Download Pool Tip #61: Coming Soon (PDF format, 0KB)

Download Pool Tip #60: Coming Soon (PDF format, 61KB)

Download Pool Tip #59: Safe Pool Chemical Storage Practices (PDF format, 35KB)

If you store or use hazardous chemicals at your pool site, you are vulnerable to accidents which can lead to injury, death, downtime, elevated maintenance costs, bad PR, and loss of customer confidence. Accidents and releases of hazardous materials into the environment are preventable. All pools should develop a Chemical Safety Management Plan. Start by taking inventory of the hazardous materials on site. List the chemicals, their quantity and where and how they are stored.

Determine what can go wrong by using the “What if…?” hazard analysis method. For example: What if someone mixed the muriatic acid and sodium hypochlorite? What if a child picked up a trichlor tablet and bit into it, thinking it was candy? What if a contaminated barrel of calcium hypochlorite exploded then started a fire?

Assess the likelihood of accidents, and evaluate potential consequences of accidents if they occur. Establish a preventative maintenance program and standard operating procedures for handling chemicals. Gather MSDS sheets, provide MSDS stations and train staff on the information provided on the chemical labels and in the MSDS sheets. Properly label all hazardous materials. Implement employee training and retraining programs. Develop an emergency response plan and practice emergency procedures. Document and investigate accidents if they occur.

Safe Chemical Storage

• Do not allow children to handle pool chemicals
• Don’t smoke near pool chemicals
• Store chemicals in a cool, dry, well ventilated area
• Separate incompatible chemicals
• Keep pool chemicals away from flammable products
• (paints, solvents, soaps, detergents, fertilizers, pesticides, oils, fuels, acids…)
• Store chemicals on pallets or shelves, not on the floor
• Follow chemical manufacturer’s stacking procedures and storage guidelines
• Store liquid chemicals below solid chemicals
• Keep the chemical storage area clean
• Inspect chemical containers regularly
• Use chemicals on a first in, first out basis
• Wear appropriate protective gear when handling chemicals (eye, skin, and respiratory protection)

Download Pool Tip #58: Pool Water Temperature (PDF format, 21KB)

Here’s something you will never get two people to agree on. Water temperature preferences vary from person to person, depending on their age, health, the activity in which they are participating, and what they have become accustomed to when they enter a pool.

What is considered to be an appropriate pool water temperature varies by region of the country. For example, pools are usually kept colder in New England and warmer than average in Florida. Typically, spas are maintained at 104° Fahrenheit. Multi use pools are usually kept at 83° – 86°, while competitive pools are usually maintained at cooler temperatures between 78° – 82°. Depending on the target population, instructional and therapy pool water temperatures usually range between 86° – 94°.

As water temperature increases, costs of pool operation also increase. Besides the obvious cost of energy to heat the pool and surrounding area, evaporation rates speed up and destruction to the surrounding equipment and surface materials intensifies. Chemical usage goes up. Calcium is less soluble in warm water, so water is more difficult to balance and problems associated with calcium scale deposits mount. Perspiration rates increase and more ammonia is added to the pool. Chloramine levels escalate rapidly as a result. Organic loading escalates. TDS levels also increase at a faster rate, requiring more frequent dilution, and draining and refilling of the pool.

Pool operators should select a temperature based on priority facility usage and programming, and age of participants, while managing the maintenance concerns.

Cooler water temperatures are needed for: high level competitive or fitness swimming, aerobic fitness activities, and activities in which participants are generating a lot of heat that needs to be dissipated. Warmer temperatures are needed for instructional programs, low level fitness and health maintenance programs, therapeutic programs, and programs catering to young children or seniors.

No matter what the water temperature, someone is likely to complain that the water is either too warm or too cold. If a patron tells you the water feels too warm, tell them not to wear a bathing cap, to drink plenty of water, and to reduce the level of intensity at which they are working out. If the water feels too cold, suggest they wear a bathing cap, wear a Lycra dive skin, rash guard or neoprene wet suit, and work faster and harder so that they use more energy and generate more heat.

Ambient air temperature in indoor pools should be maintained for the comfort of participants and instructors, coaches or therapists who are in the water – not for spectators on the deck who are dressed in street clothes. To prevent excessive loss of heat due to evaporation, make sure air temperature is always maintained 1-3 degrees warmer than pool water temperature. Relative humidity should be maintained around 50%. At a minimum, ventilate in compliance with ASHRAE Standard 62-1989 “Ventilation for Acceptable Indoor Air Quality”. Provide at least 8 complete air exchanges per hour in the natatorium with a minimum 40% fresh air. Make sure you have the capability of bringing in 100% fresh air when needed. Since pollutants travel from positive to negative pressure areas, natatoriums should be positively pressured in relation to the out of doors, and negatively pressured in relation to surrounding occupied spaces. Maintain air contaminants below specified values or concentrations.

Drafts, stratification of air, thermoclines or temperature gradients should not be evident. The air velocity in the area from deck level to 8′ above the deck should be less than 25 feet per minute. Air should be introduced into the pool area from low to high. A common design error is to install all ductwork at ceiling level. Supply registers should be placed low in the natatorium and grills adjusted so that fresh air blows across the pool surface. This is necessary even though it increases the rate of evaporation, because heavier than air pool chemical gasses need to be moved away from the pool surface.. Return/exhaust ducts should be located at ceiling level.

The air temperature in spectator seating areas should be cooler than the air in the natatorium, and the velocity should be higher, in the range of 40 – 50 fpm. Better yet, design a spectator viewing room adjacent to the pool deck, and separated from the pool deck by safety glass windows. The room should be large enough to accommodate the anticipated number of spectators, allowing at least 20 square feet per person. Depending on the season, the viewing room should be heated and/or air conditioned and the temperature in the room maintained for the comfort of the spectators. Comfortable seating, coat racks, vending machines, reading materials, toys, televisions and other distractions are often provided to help keep people occupied while they wait.

Download Pool Tip #57: Circulation Pattern Dye Testing (PDF format, 20KB)

Pool operators typically use sodium fluorescein (AKA: Solvent Yellow 73, Acid Yellow 73, Fluorescein Disodium Salt, Uranine, Fluorescein Water Soluble) to test water circulation patterns, look for circulation “dead spots” and leaks in pools, and evaluate inlet operation.

To use sodium fluorescein, first read the MSDS sheet for the sodium fluorescein provided by the chemical distributor. Clear the pool of bathers, and allow the water to settle for a few minutes. Make sure the water is at the proper level.

Put on protective goggles and disposable latex gloves to prevent skin contact with the dye. Empty the container of dye into the surge chamber, or skimmer basket or gutter drain nearest the pump. Use approximately 3 ounces (a small Dixie Cup full) per 100,000 gallons of pool water.

If your pool has water–to–waste rather than recirculating gutters, turn off the circulation pump and isolate the hair & lint strainer. Remove the strainer lid, empty the contents of the container into the basket and replace the lid. Then open the valves to permit normal water flow through the hair & lint strainer, and turn the circulation system back on.

Start the video camera and record the test for future reference, or prepare a chart showing the pool and location of all inlets. Number your inlets on the diagram. Wait one to three minutes. Water dyed a bright, fluorescent yellow–green color will then be seen entering the pool through one of the return inlets. While dyed, the pool will glow in the dark when exposed to black light. Record which inlet through which the color was first observed entering the pool. Record the order of color introduction. Document the inlet pattern, any inlets that don’t work, inlets where the water stream was weak, inlets pointed in the wrong direction, or inlets in need of adjustment. Observe the circulation pattern. Look for circulation “dead spots” where the water does not change color, and record.

After 10 minutes, or when the dye reaches all areas of the pool, stop the test. Depending on the condition of your pool circulation and filtration system, whether the pool is located indoors or outdoors, and the length of turnover time, the water soluble dye should disappear completely in a time frame ranging from less than 15 minutes to a maximum of 4 hours. It won’t hurt bathers to swim in the pool while the dye is still present, but explain to them why the pool water is discolored.

If you spill any powdered dye on the deck, just dilute it and wash it down the deck drains. If you get full strength powdered dye on yourself, scrub with soap and water (–– it may take a day or so to remove all traces of color). Do not breathe or swallow the dye. If you spill dye on your clothes, just wash normally in the washing machine with detergent and water.

Crystal violet is also commonly used as a dye for evaluating pool circulation patterns. The test is conducted in a similar manner with a few notable exceptions. Since the purple color produced by crystal violet will not appear in the presence of chlorine, all traces of chlorine must be removed from the pool prior to starting the test. Add sodium thiosulfate to the pool at a concentration of 1 ounce per 1 ppm per 10,000 gallons of pool water. For example, to remove 2.5 ppm of chlorine from a 360,000 gallon pool, 5.6 pounds of sodium thiosulfate would be needed.

Ex. (1 oz) (2.5 ppm) (36) = 90 ounces ÷ 16 = 5.6 pounds

After the chlorine has been removed from the pool, pre mix crystal violet with water (25 grams per 2 gallons of water) and pour the solution into a skimmer or gutter drain. Use 25 grams, about one ounce, of crystal violet for each 67,500 gallons of pool water which will be dyed. To remove the dye once the test is completed, turn on the chlorinator and inject chlorine into the return lines.

Sodium fluorescein or crystal violet can usually be purchased from your local specialty pool chemical distributor, or can be ordered directly from a chemical manufacturer.

Download Pool Tip #56: Pool Water Testing (PDF format, 52KB)

As most experienced pool operators know, it’s usually easier to avoid a water chemistry related problem than it is to solve it. For instance, it’s difficult to eliminate an algae bloom once it has discolored and clouded the water. By time patrons are complaining of skin rashes, dermatological problems, or bacterial infections acquired from contact with contaminated pool water or poorly ventilated natatorium air, it’s too late to prevent the spread of the disease. Once the pool walls are stained, or pool equipment has corroded, the damage has already occurred. By frequently monitoring the chemical content of water, accurately testing the ingredients of the water using quality test reagents and instruments and proper water sampling techniques, calculating proper dosages of chemicals needed for adjustment, correctly applying chemicals to the pool, and maintaining recommended levels, many costly and time consuming water chemistry problems can be prevented.

Pool operators should become more familiar with good water testing and analysis practices, and be knowledgeable about common water tests, the recommended frequency of performing testing procedures, various types of test kits and instruments available, proper testing methodology, how to avoid common testing errors, and the importance of keeping accurate records of water test results.

Proper Testing Methods

Test results should be consist and repeatable. Two different people performing the tests at the same time should get the same results. It is important to carefully read and follow the test kit manufacturer’s directions.

When analyzing pool water, it is important to obtain a representative sample of water from the pool. It is best to gather water samples from at least 12 to 18 inches below the surface of the water. Do not take water samples in close proximity to perimeter return inlets, nor directly from the return lines in the pump room. If dye tests have indicated the presence of circulation “dead spots”, make sure that samples are taken from several areas of the pool, and from both the shallow and deep ends of the pool.

Use a clean, plastic water sample jar. Rinse the jar with pool water several times before collecting the water sample. While holding the jar up–side–down and in a vertical position, plunge the jar below the water surface. When the water level is at your elbow, tilt the jar into an up right position and let the jar fill with water. Cap the jar while its still submerged. If you are taking samples from more than one pool, make sure to label the sample jars so you don’t accidentally mix up the samples.

Many test reagents are temperature sensitive. Directions may indicate that sample water should be allowed to cool to room temperature before tests are performed. After allowing the water to cool, perform the tests within a reasonable amount of time so the water constituents do not change.

Take the water sample jars, test reagents and instruments to a well lit room away from the pool deck. Do not wear sunglasses when interpreting test results. Follow the test kit manufacturer’s directions closely in order to obtain accurate results. Make sure all testing equipment and test cells are clean. Adding a reagent to a cell which contains traces of reagents from past tests will affect the accuracy of the test. Empty and rinse all testing instruments after each use. Use fresh reagents, and only apply reagents designed to be used with a specific test kit. Do not interchange or substitute reagents from one manufacturer with those from another test kit manufacturer. Color standards, color intensity and concentration may be different. Hold the test cell at eye level and fill test cells with the sample water to the indicated line, making sure the bottom of the meniscus curve touches the cell fill line.

When using liquid reagents, always hold the reagent bottle in a vertical position. If you hold the bottle like you would hold a pencil, the reagent drop sizes will not be uniform. Make sure you don’t accidentally interchange the reagent caps. Put the same cap back on the bottle from which it was removed. Replace the caps on reagent bottles immediately after performing the test. Reagents will react and begin decomposing when exposed to air and their shelf life will be diminished. If you lose count of the number of drops of reagent you’ve added to a sample, discard the sample and start over.

If you are performing tests which require the use of tablet reagents, do not touch the tablets when you remove them from their foil packets. If the foil packets are torn, or the tablets have gotten wet, discard the reagents.

If using dip and read test strips, bottle caps should be replaced immediately after use. The strips will become reactive with moisture in the air. Check the timing of the tests –– the colors change if you wait longer than the time specified. Remember to follow the manufacturer’s directions. Many of the tests involve a two step process. For example, total alkalinity, pH, total hardness, and cyanuric acid results are read after 30 seconds, then the test strip is re dipped, swished for an additional 30 seconds and then chlorine and bromine results are read immediately.

Make sure all testing instruments are properly calibrated. Avoid dropping instruments on the pool deck, do not expose test instruments to high levels of humidity, and do not fully submerge testing instruments unless they are sealed and the o–ring or seal is intact.

Make sure the test kit you are using is capable of giving a reading in the range you are likely to encounter in the pool. Purchase wide range test kits. Dilution testing can be complicated and the operator is more likely to make an error. Watch for bleaching, unusual color appearance, difficulty reaching an end point because sanitizer levels are elevated, tests results which are not within range of the reagent being used, or metal ions that are masking out the titrant and interfering with the tests.

Directions may indicate that a sample should be swirled rather than shaken. If you shake a sample meant to be swirled, oxygen or carbon dioxide in the air will dissolve in the water producing bubbles which may alter test results. If test cell caps are lost or destroyed do not use your fingers to cap test cells, you’ll contaminate the sample. Have a supply of extra test cell caps available. Never add test reagents directly to the swimming pool in order to do a quick “flash test”. It’s not very professional and the results are worthless.

Most reagents have a relatively short life span of less than one year. However, some reagents can go bad in an afternoon if improperly stored. Reagents are stamped with an expiration date, and should be discarded and replaced if they have expired. Store reagents in a cool, dark location. High temperatures may cause reagents to go bad. Do not store reagents on the pool deck in direct sunlight, in the trunk of your car, or in the pump room on top of the heater. Heat and ultraviolet light degrade many common reagents. Do not allow reagents to freeze either, because reagents may crystallize and become useless for further testing. Don’t store reagents in a chemical storage area. Pool chemicals, other reagents, and air can be absorbed and contaminate the reagents.

Common Water Tests

Tests should be performed to make sure acceptable chemical levels are being maintained. The operator should look for problems that might contribute to poor water clarity, produce favorable conditions for bacterial and algae growth, cause the water to irritate bathers, or lead to staining and destruction of pool components. Tests kits and instruments should be purchased so the following items can be monitored:

• Free, total and combined chlorine
• Total bromine, or other sanitizers and oxidizers if used
• Cyanuric acid
• Bacteriological water quality
• Oxidation reduction potential
• ph
• Acid and base demand
• Total alkalinity
• Calcium hardness
• Total dissolved solids
• Metals: iron, copper, manganese
• Nitrite and nitrates
• Phosphates
• Clarity
• Water and air temperature
• Relative humidity
• Dissipated chemicals over the pool
• Saturation index

Test Frequency

It is necessary to diagnose water problems before they can be solved. Constant monitoring, evaluating and adjusting of the water ingredients will lead to consistent water quality. Large fluctuations in water chemistry may necessitate costly and time consuming rectification. Several factors govern how often water tests should be performed, including the parameter’s tendency to change rapidly, bather load, pool volume, water temperature, turnover time, amount of sunlight shining on the pool, the surrounding environment, code requirements, and whether the pool is residential or commercial. The content of the source water and the dilution rate based on the amount of fresh water being added to the pool can also influence the need for frequent testing.

Pool water should always be tested and corrections made before allowing patrons to enter the water on a given day. Heavily used commercial pools should be tested at least once every one or two hours. Small apartment pools which are primarily decorative and only used by a half dozen residents on an average day may only need to be tested twice or three times per day. Sanitizer levels and pH should be checked at every test. Some chemical levels, like calcium hardness or TDS, are slow to change and need only be performed daily or weekly. Water chemistry changes can occur so rapidly in warm water, heavily used commercial spas that testing, monitoring of pH and ORP, and chemical adjustments must be augmented by the use of automated controllers.

Test Kits and Testing Instruments

Test kits, chemical reagents and testing instruments must be available so that detailed water analysis can be conducted by the pool operator and all chemical levels can be maintained within acceptable ranges. Regardless of the cost or sophistication of the testing equipment, the tests must provide reliable, accurate, repeatable results. Directions should be easy to follow. All staff members required to perform water tests should be thoroughly trained in the use of the testing equipment. Some of the more common types of test kits and instruments found at commercial pools include:

Color Comparitor

Liquid or tablet reagents are added to a water sample and react with a chemical present in the water to produce a color of a specific intensity or shade. Reagents are chemicals used to measure, detect, or analyze another chemical. The color of the test sample is compared to a printed color chart, or liquid encapsulated color standard. Accuracy of test results is somewhat subjective and depends heavily on lighting conditions and the pool operator’s visual ability to differentiate color graduations. (Commonly used to test for chlorine, bromine, and pH).

Colorimeter

Just as is done when using a color comparitor test kit, liquid or tablet reagents are added to a water sample and react with a chemical present in the water. Then the sample is placed in a colorimeter chamber or filter photometer and capped to shield outside light. The pool operator presses a button on the battery operated meter and a light beam is passed through the test tube containing the sample. The amount of light which passes through the sample is detected by a photocell, which then responds by sending an electrical current in proportion to the amount of light detected to an analog or digital display on the meter.

Some colorimeters require that the results be converted using calibration graphs requiring some analytic skills, but most meters being sold to the pool industry today are calibrated to perform specific tests and use an appropriate light color or wavelength so that results can be direct–read. Results from a colorimeter are more accurate and reproducible than those obtained using color comparitors because they do not depend on human visual acuity or ambient light levels. Metering instruments are much more sensitive to tiny variations in color.

Titration

A color change occurs as a measured indicator reagent is added to a test sample. A titrant is added, depending on the manufacturers directions, either drop by drop or by depressing a plunger on a syringe to dispense the titrant until a second distinct color change occurs when an end–point is reached. The amount of titrating reagent added to cause the color change is related to the concentration of the chemical in the sample. Titration is commonly used to test chlorine, bromine, total alkalinity, and calcium hardness levels in pools.

For pool operators who are color blind, or who have trouble color matching or differentiating colors when chlorine levels are greater than 3.0 ppm, titration rather than color comparitor test kits should be used to obtain accurate results.

Two scoops of buffered DPD indicator powder are added to a 25 milliliter pool water sample, turning the sample pink. FAS (ferris ammonium sulfate) titrant is added drop by drop, swirling after each drop, until the sample goes colorless. The endpoint is reached when the pink sample turns to clear. The number of FAS drops added is multiplied by an equivalency factor of 0.2 to obtain a free available chlorine reading to an accuracy of 0.2 ppm. It is possible to tell for instance that a spa contains exactly 9.4 ppm of FAC.

Then to the same sample, DPD reagent #3 is added. If the sample does not change color, no combined chlorines (chloramines) are present. If the sample turns pink again when DPD #3 is added, the FAS titrant is added again drop by drop until the sample turns clear. The total number of FAS drops added in both the free and total tests multiplied by 0.2 is the total available chlorine reading.

The same kit can be used to test for bromine by multiplying the answers by 2.25, the molecular weight difference between chlorine and bromine, or a special FAS kit for testing bromine can be ordered.

Turbidometric

A test reagent, typically melamine for cyanuric acid level testing, is added to the water sample and forms a suspended non soluble compound or precipitate which clouds the water sample. The higher the chemical concentration, the greater the cloudiness of the solution. The sample is pored slowly into a calibrated test cell until an indicator dot at the bottom of the cell is no longer visible. Some kits raise or lower a test stick down into a test cell instead. When the indicator dot is obscured, the water level in the cell is compared to the calibration scale on the side of the cell. Test results can be read visually or by a photometer.

Neflometric

Neflometers are used to measure water clarity. The meters are usually battery operated, and can test in the range of 0 to 1,000 NTUs without the need to perform calculations or interpolate calibration charts, with a resolution of 0.1 NTUs. The detector compensates for sample color, stray light and light fluctuation. A water sample is taken from the pool, the meter is switched on, the sample solution is placed in the meter, a narrow beam of light is passed through the sample and scattered by the particles. A light detector and a scatter detector collect the light. The digital display can be read directly within approximately 10 seconds.

Laser particle counters are also available, but are out of the price range of most recreational water organizations. However, water samples can be sent to laboratories for laser particle analysis to determine filter efficiency and capability of particle size removal.

Electrometric

Portable electrometric meters are used to measure pH, total dissolved solids, and oxidation reduction potential. An electrode or electrical probe is inserted in a test sample, the battery operated meter is turned on, electrical current passes between the electrodes, then the results are displayed on an electronic meter.

Some of the meters have automatic temperature compensation, and automatically turn off after a set period of interruption to extend battery life. Devices range from simple, low cost hand held pocket meters to professional laboratory instruments. It should be remembered though, that the inexpensive devices will not have the accuracy of quality laboratory instruments.

The meters must be calibrated frequently, as often as daily. Some meters use a calibration solution of a known standard in order to avoid drift. Others have screwdriver or push button calibration adjustment. The operator must be careful not to drop the meter on the pool deck, or fully submerge the instrument, unless the meter is designed to be immersed (and most are not).

Dip–and–Read Strips

Plastic strips with chemically treated reagent pads, are dipped in the water, and removed. After a 30 second wait for a chemical reaction to take place and color to develop, the reagent pad color is matched to the color patches on the strip container. Single or multiple test strips are available to test for chlorine, bromine, cyanuric acid, nitrite, nitrates, pH, total alkalinity, calcium hardness, and polymeric biguanides. Test strips have a shelf life of between 10 and 20 months depending on the specific test.

Test strip technology was originally developed for the medical industry, and has been adapted for use in the swimming pool industry. The test strips are quick and easy to use, and are a good, quick way to identify problems and determine when further testing needs to be done.

Thermometer

A water thermometer with a direct reading dial on a stainless steel stem probe, with a battery operated analog or digital display is recommended for measuring pool water temperature. The probe is inserted into the pool for a few seconds in order to obtain a result. Inexpensive plastic or glass thermometers which are often tied to a pool ladder or rail and left in the pool are easily broken or stolen. And as every pool operator knows, if a thermometer is left in the pool, patrons will come complain about the water temperature. Half of them will insist the water is too cold, while the other half will complain that the water is too warm.

Volumetric Pump

Volumetric pumps are used with various gas detector tubes to measure airborne contaminant gasses or vapors in the air over the pool, and insure that contaminants are within safe levels specified by OSHA for work environments. Pool operators typically test for chlorine, ozone and carbon dioxide six inches above the pool water surface.

Detector tubes are purchased separately for each of the specific gasses needed to be tested, within a measurable concentration range, usually in boxes of 10 or 12 tubes.

To perform a test, a gas detector tube is selected, the ends of the glass tube are carefully snapped off, the detector tube is inserted into the pump, the pump is stroked and a precisely measured, representative ambient air sample is drawn through the tube and into the pump. Some tests require multiple air samples of an indicated length or volume. Many of the pumps have stroke counters and end–of–stroke or flow finish indicators to help insure more accurate measurements. The chemical vapor drawn into the tube reacts with a reagent and stains the material in the tube. A chemical reading is obtained by observing the stain and referring to the calibrated scale printed on the indicator tube.

If test results show overexposure to a regulated chemical in excess of the permissible exposure limit (PEL) and the level of contaminants cannot be reduced, adjustments must be made in work hours, the environment, or work policies and procedures.

Dosimeters

In order to comply with the OSHA “Confined Spaces” Regulation [29 CFR 1910.146] the employer must provide testing and monitoring equipment at no cost to employees, maintain testing and monitoring equipment properly, and ensure proper use of testing equipment by employees. Before an employee enters a confined space, internal atmosphere of the confined space must be tested with a direct reading, calibrated instrument (dosimeter), for: oxygen level, flammable gasses and vapors, and toxic air contaminants such as hydrogen sulfide, and carbon monoxide.

Most dosimeters have a sensing cell or probe mounted on the end of a cable or wand which is attached to a sampling hose, pump and monitor. Dosimeters are battery operated, have digital read–out displays, and visual and audible alarms that sound to warn the employee of dangerous conditions within the confined space.

The regulation exists to protect workers who must enter confined spaces in order to perform their jobs. In an aquatic setting, large pool filter tanks and surge chambers would be considered confined spaces. The regulation also requires that employers must provide a lifeline and retrieval system, provide harnesses for employees which must be worn when entering a confined space, post a floor sign when employees have entered a confined space, provide annual inspections to insure proper operation of the rescue and recovery winch, purchase a ventilation blower to provide steady, fresh airflow to confined spaces and reduce contaminant levels. The employer must also establish a permit system and controlled entry authorization procedures, and train personnel for confined spaces operations.

Record Keeping

Pool chemical logs are one of the most important records which must be kept in an aquatic facility. The records can provide data for determining costs of operation, chemical purchases, patron satisfaction, causes and prevention of disease, and for budget recommendations and justification for future expenditures. The daily pool chemical log should be posted. State, federal and local ordinances may require that certain water tests be performed and records maintained to ensure the safety and health of the public. Well maintained documents may be used as part of a successful legal defense in cases of accidents resulting in litigation.

Records should be completed accurately and on time, summarized for the facility owner or aquatic supervisor, and stored for an extended period of time in case documentation or retrieval of information is necessary. Do not forge test results. If it can be shown that pool logs were filled out without the actual water tests being made, the documents will be worthless to your defense. Most state codes require that pool chemical and maintenance logs be kept for a period of not less than 1 to 3 years. However, records should be kept indefinitely if there is any chance they might be needed for review in a legal matter.

Additional Information

For more information on pool water testing, the following resources are recommended:

“Standard Methods for the Examination of Water and Wastewater”. Edited by Clesceri, L. S., Greenberg, A. E., and Trussell, R. R., and published by a joint committee of The American Public Health Association, American Water Works Association, and Water Pollution Control Federation. This 1,500 + page book was originally published in 1905, and is in its 20th edition. The comprehensive text covers everything you ever wanted to know about water testing, testing methods and analysis. The book can be found in most research libraries or can be purchased for around $155.00.

“Pool/Spa Water Chemistry and Testing Video”. This video is available in VHS format, and examines water chemistry and testing in detail. The video and the accompanying workbook can be ordered from Taylor Technologies.

Download Pool Tip #55: Pseudomonas Aeruginosa (PDF format, 27KB)

In recent years, pool operators across the country have been reporting Pseudomonas aeruginosa outbreaks at their facilities, in record numbers.

Pseudomonas aeruginosa is a gram negative bacterium present in the environment. It is passed into the pool water from the human skin and gastrointestinal tract, and frequently through broken pool circulation pipes, or from dirt tracked onto the pool deck. Pseudomonas aeruginosa is often cultured from warm, moist environments, particularly when turbulent or aerated, because the bacteria grows rapidly under these favorable conditions. Because of this fact, many aquatic professionals mistakenly believe that Pseudomonas is only a problem in warm water pools and spas. Unfortunately, Pseudomonas can grow in swimming pool water as well as spa water, on the pool edge and decks, into filter liners, in the filter sand bed, and inside PVC pipe, racing lanes, and water hoses.

If bacteriological analysis of pool water is not performed on a regular basis, a pool operator will probably be unaware of the contamination problem until bathers start complaining of infection. Bathers who spend lengthy amounts of time soaking in a spa, staff members who wear wet bathing suits throughout their work shift, or patrons who swim regularly for extended periods of time are most likely to experience problems.

The most common sign or symptom of a P. aeruginosa infection is a dermatological problem resulting in a red, bumpy, itchy rash, which looks like measles. On most bathers, the rash appears on the legs, trunk, inside of the arms, lower back, neck and shoulders, or anywhere the skin is broken, or where a swim suit rubs against and irritates the skin.

Pool associated folliculitis or skin rashes from Pseudomonas aeruginosa can be prevented by taking a soapy, hot water shower in the nude, immediately after leaving the pool, and before cooling down and allowing the pores to close over the bacteria.

According to the Centers for Disease Control, other symptoms associated with P. aeruginosa infection include: earaches (otitis externa), breast inflammation (mastitis), feeling ill (malaise), inflammation of the eye membrane (conjunctivitis), coughing and sore throat caused by inflammation of the mucous membrane of the pharynx (pharyngitis), fever, lymph gland inflammation (lymphadenopathy), urinary tract infections causing impaired ability to pass urine (dysuria), flu–like symptoms, and nausea.

Although it is not uncommon to find Pseudomonas bacteria present in pool water, Pseudomonas aeruginosa outbreaks rarely occur in properly treated and rigorously maintained public aquatic facilities. To prevent the uncontrolled growth of P. aeruginosa, the following practices are recommended:

Collect water samples from the pools and spas, and take swabs from inside the filters, on a regular weekly basis for bacteriological water analysis. Simple tests for Pseudomonas are available, and can be done by the knowledgeable pool manager. If samples are sent to an independent laboratory, specifically request that tests for both the presence, and quantity, of Pseudomonas be performed.

Pressure test the pool recirculation systems to make sure there are no suction side breaks in the lines which may be allowing dirt to enter the closed systems.

Institute rigorous deck maintenance procedures. The purpose of cleaning a pool deck is two–fold. Oil, grease, dirt and debris must be removed through sweeping, rinsing, power washing, and scrubbing the pool deck with an all–purpose cleaner, detergent, or degreaser which is compatible with pool water. But more importantly, decks must be disinfected to prevent bacterial growth, including P. aeruginosa, and the formation of a slippery biofilm layer. The best, and least expensive way to disinfect a pool deck, is to spray a 20 to 1 solution of water and sodium hypochlorite on the deck, and rinse with a high pressure nozzle and hose. For clean–up of blood or bodily fluids, and to comply with the OSHA regulations for preventing transmission of bloodborne pathogens, the decks, or any contaminated surface, should be cleaned with 5.25% sodium hypochlorite (household bleach) diluted to between 1:10 and 1:100 with water. This is equivalent to disinfecting with a 1:20 solution of 10–12% sodium hypochlorite (liquid pool chlorine). Clean and disinfect the decks on a nightly, or at least twice weekly basis, depending on the level of facility use, and, immediately after any contamination with blood or bodily fluids.. Attempt to keep patrons in street shoes off the deck, or at least away from the pool edge.

Require that infants and young children who are not yet toilet trained wear tight fitting rubber pants or swim suit diapers while in the pool.

Shock spas daily and pools at least weekly, or as needed if combined available chlorine levels exceed 0.2 ppm. Make sure that you allow enough time for the chlorine to reach the breakpoint. Double check your calculations to make sure the correct amount of chlorine is being used. Inject the chlorine into the return lines using a chemical metering pump, or install a slurry feed bucket so that large amounts of chemicals can be poured into the return lines. Do not hand feed or pour the chlorine directly into the pools. Do not remove high levels of chlorine from the water with sodium thiosulfate. Let chlorine levels return to normal gradually after the breakpoint has been achieved.

Install an automated pH/ORP controller, or at a minimum, purchase a portable ORP meter. Maintain a minimum 750 mV oxidation reduction potential in commercial pools and spas. Oxidation reduction potential (ORP) is a standard method of a measuring the chlorine’s (or bromine, ozone or other sanitizer–oxidizer’s) ability to oxidize and sanitize the water. ORP sensors measure HOCl conductivity of water, the potential generated for oxidation, and permit constant monitoring of sanitation levels. ORP takes into consideration all water constituents, including oil, grease, TDS, cyanurates, and organic contaminants. It is a true measure of water cleanliness. ORP falls whenever pH is either high or low, and when TDS, chloramine or cyanurate levels are high. Organic and chemical loading drastically reduce the ability of the bactericide to overcome bacteria. The amount of chlorine needed by weight in parts per million (ppm) in order to maintain a 750 mV ORP level will vary from pool to pool depending on other water constituents. 650 millivolts of ORP is the minimum recommended level for residential pools and drinking water promulgated by the American Water Works Association (AWWA). The German DIN Standard recommends a minimum 750 mV ORP for commercial pools and spas.

Buy fresh chlorine and other pool chemicals from a reputable vendor, rather than from a mass merchant or local store where the chemicals may have been sitting in a warehouse or on the shelf for a lengthy period of time. Store chlorine in a cool, dark, well ventilated location. Some forms of chlorine have a very short half life and lose their effectiveness rapidly when exposed to heat or ultraviolet light. If sodium hypochlorite (liquid chlorine or bleach) is used as the primary bactericide, purchase a sodium hypochlorite test kit. Sample and test all sodium hypochlorite deliveries for percentage of available chlorine. Use sodium hypochlorite on a first in, first out, basis.

Don’t use defoamers in the spa. Defoamers only change the water surface tension and hide, rather than correct, the problem. Defoamers are wetting agents that prevent foaming, or that neutralize and dissipate suds in aerated spas, fountains and hydrotherapy pools. Foaming in pools can be caused by: soft water, quaternary ammonia algaecides, body lotions and suntan oils, tile cleaners, high TDS levels, air pollution, body fats secreted by the sweat glands, and oils from the skin. Foaming water is usually an indicator that the water in the pool or spa needs to be changed. Discontinue use of the product which causes foaming or drain and refill the pool.

Drain and refill the pool and spas when total dissolved solids exceed 1,500 ppm. Dilute the water regularly to control for TDS build–up which might be interfering with the chlorine’s ability to sanitize and oxidize. If scheduling, or regulations enacted as a result of drought conditions prohibit the draining and refilling of a pool, consider installing a nanofiltration system to purge the water of dissolved solids.

If high levels of Pseudomonas are found in the pool, the following procedures should be followed. Rinse pool circulation pipes and equipment with high levels of chlorine, then drain the pool completely. Remove the sand or other filter media from the filter tanks, and dispose of the media properly.

Read the material safety data sheets (MSDS) before beginning work. Make sure that the area in which you are working is extremely well ventilated. Do not work alone. Both you and your partner should be knowledgeable in first aid procedures for chemical burns, and respiratory emergencies in case one of you is overcome by fumes. Don protective clothing that covers all areas of exposed skin. Wear goggles and a half mask respirator with fresh chlorine cartridges and particle filters, rubber boots and neoprene gloves.

Scrub the entire surface of the pool, the decks, and the interior of the filter tank with a solution of 1 part sodium hypochlorite to 20 parts of water. Spray the chlorine mixture or pour the mixture from the deck down, a small area at a time. Keep the rinse water on at all times, and rinse frequently with fresh water to cut down on the fumes. Do not allow the chlorine to collect in the bottom of the pool, and neutralize the chlorine before pumping it to waste. Refill the pool, add chelating agents, balance the water, and closely monitor the sanitizer levels.

Download Pool Tip #54: Ozone Generators (PDF format, 24KB)

Ozone is activated oxygen or O₃. Ozone was named by C.F. Schoenbein in 1840, and its name is derived from the Greek word “ozein” which means “to smell”.

Ozone was first used for drinking water disinfection in 1893 in Oudshoorin, The Netherlands. Nice, France began disinfecting its public water supply in 1906 and still does today. Potsdam, New York was the first U.S. city to treat its drinking water with ozone. The largest ozone generation plant in the world is in Los Angeles. The L.A. plant can treat as much as 600 million gallons of water per day. Ozone is also use to treat air, and sewage.

Pool disinfection with ozone has been common in Europe since the 1950’s. A swimming pool ozone system was displayed at the 1939–1940 New York World’s Fair. The first pool in the U.S. to use CD (corona discharge) ozone to treat its water was the Lake Mohawk Cruiser Swim & Tennis Club in Byram, New Jersey. The system was installed in 1937.

Two common methods of producing ozone on–site for swimming pool and spa water oxidation and sanitation exist.

In the ultraviolet light method of ozone generation, air is passed near special mercury vapor UV lamps made of quartz glass that produce light of a specific wavelength. Oxygen molecules, O₂, are bombarded with UV rays and recombine into ozone, O₃, but in very low concentrations.

In the side stream, corona discharge method, the preferred method of generating ozone on–site for pool water treatment, air is first oxygen enriched then dried to prevent nitric acid from forming. The oxygen enriched, dried air is then sent past a di–electric or high voltage electrodes, which give off a bluish glow or “corona discharge”. O₂ is split into individual oxygen atoms which recombine into O₃. The ozone is then injected through a venturi and transferred into a side stream of water drawn off the pool water return line. Corona discharge ozone systems should also include the use of contact chambers and may include degassing units similar to those used in the larger and much more expensive European model ozone generation systems, to treat pool water and remove the ozone from the water prior to its entering the swimming pool.

The goal of side stream sizing is to achieve one complete turnover of water in a given period, or to cause all the water in the pool to be ozonated at a given percentage of side stream. Volume of the pool in gallons is divided by the time factor in minutes in a day, and then by the actual flowrate in gallons per minute. For example, a pool containing 95,000 gallons of water divided by 1,440 minutes in a day divided by a flowrate of 265 gpm (a typical 6 hour turnover rate), equals 0.248. Therefor, a minimum 25% side stream is required. The side stream is usually sized at between 25 and 33 percent, however, if you reduce the side stream, the dose concentration goes up inside the contact chamber.

Ozone generator sizing is based on the formula “___ gallons per minute multiplied by 0.227 grams per gallon multiplied by 0.4 milligrams per liter equals ___ grams per hour”. Derivation of the 0.227 conversion constant for use in calculating ozone generator size is based on water flow rate, gpm times Xµ times ppm = grams per hour. Xµ equals grams per hour times minutes per gallon. Xµ equals 60 minutes per hour times grams per gallon. 1 ppm is equivalent to 1 milligram per liter which equals 0.00379 grams per gallon. Therefore, X = 0.00379 grams per gallon times 60 minutes per hour, or X = 0.2271 grams per gallon.

The goal of contact chamber sizing is to achieve enough contact time between the ozone produced and water in the side stream to allow at least 4 minutes of retention of the side stream flow in a contact chamber, tower, or vessel, and an ozone dose of 1.6 ppm in the side stream when ozone is the primary oxidant. CT values of at least 1.6 are achieved when the concentration of ozone in milligrams per liter equals 0.4 for a time of 4 minutes. Flowrate in gallons per minute is multiplied by 4 minutes to determine the minimum size of the contact vessel in gallons.

When sizing ozone generating systems for different types of facilities with different user profiles and characteristics, it becomes obvious that one size does not fit all. When comparing units for purchase, ask the manufacturer to provide an individualized report recommending a generator size based on grams per hour and pounds per day of ozone production, as well as the parts per million dose on main filtration. Side stream in gallons per minute and percentage of main flow should be provided along with electrical specifications, oxygen feed gas flow, and cooling water requirements. Contact tank, degassing valve, ozone destruct, injector, booster pump and ambient ozone monitors models and sizes should also be suggested.

Ozone is an excellent oxidizing agent –– thousands of times faster than chlorine or bromine at removing organic and inorganic contaminants and pathogens from the water. Organic contaminants such as perspiration, urine, creams, ointments, hair care products, cosmetics, nasal secretions, and creatine (a chemical normally found in blood and excreted into urine by the kidneys) are partially oxidized by ozone, reduced to nitrates, or flocculated and removed by the filters. Ozonated pool water will not foam, because ozone destroys foam causing organic compounds. Ozone will remove organic material before chlorine can react with the organics and help prevent the formation of carcinogenic substances called trihalomethanes (THM). No PCBs (polychlorinated biphenyls) form during ozonation, and ozone itself is not carcinogenic.

Elite level competitive swimmers believe they can swim faster in an ozonated pool. Swim event times can drop because of the decreased friction resulting from more complete oxidation and increased oxygen levels in the water.

Disease causing bacteria, waterborne viruses, yeasts, protozoa, cysts, parasites, spores, and amoebas can all be destroyed by ozone depending on the contact time and concentration of ozone in the water. Ozone is drawn to bacteria and explodes bacteria walls on contact

Because ozone is only being generated when the pool water is circulating, and ozone leaves no residual for killing bacteria about to be introduced into the water, it must be used in conjunction with chlorine or bromine if continuous disinfection of pool water is desired. However, use of ozone results in a reduced halogen consumption. Less bromine or chlorine are needed to maintain the oxidation reduction potential (ORP), and lower halogen residuals are required. Ozone does not dry skin, or bleach swimmers’ hair. For swimmers with halogen sensitivities, contact dermatitis problems and the resulting skin rashes will be reduced.

Ozone helps prevent formation of chloramine compounds. Eye, sinus, mucous membrane and throat irritation from chloramines are eliminated. No objectionable odor is produced. Ozone is often described as smelling “like watermelons”. Ozonated pools will only occasionally need to be shocked or superchlorinated.

Ozone will floc particulate matter increasing filter effectiveness, and the water will appear clearer, due to removal of finely suspended colloidal particles. Ozone does not contribute to the total dissolved solid (TDS) build–up, and may actually reduce the TDS because of particle coagulation. Therefore, less frequent draining and refilling of the pool is required.

Ozone is safe and inexpensive to use once the generating system is installed. Since ozone is generated on–site, from oxygen in the air, as needed, there is less storage and transportation of large quantities of hazardous materials. Ozone in pool water is not explosive and is not flammable. Ozone injection lines are under vacuum. If a leak in an ozone line should occur, air would leak into system rather than ozone leaking into the air.

Ozone helps remove metals which can discolor water and stain pool surfaces, prevents calcification, and softens the water. Ozone has no effect on pH or total alkalinity, so fewer chemicals are needed to adjust pH and water balance. Ozone destroys oils and converts them to carbon dioxide (CO₂). The use of enzymes to remove oils is not necessary and bathtub ring formation at the waterline will be reduced.

When properly sized and installed, a corona discharge ozone generation system should result in easier to maintain, less costly, and better smelling, better tasting, and better quality pool water.

Download Pool Tip #53: Problems Reaching Breakpoint (PDF format, 33KB)

Although rarely a problem in outdoor pools, since sunlight destroys chloramines, and the objectionable odors blow away, many pools operators have a great deal of difficulty ridding their indoor pools of chloramines. Unfortunately, HOCl also reacts with UV light (sunlight) and becomes an inactive chloride ion or salt (Cl–).

Some pools have enormously high bather load to water volume ratios, resulting in heavy organic loading, and high levels of ammoniated impurities in the water. Spray features at amusement parks, health club spas, therapy pools, swim school pools, and children’s wading depth pools with interactive play features, for example, often have chlorine levels unfathomable to operators of more traditional swimming pools. It is not surprising to find that an 18,000 gallon swim school pool maintained at 94° Fahrenheit having a bather load of 300 pre–school aged children per day, will have a continuing problem with chloramines. Ten thousand gallon children’s wading pools at successful commercial waterparks may have bather loads exceeding 2,000 children per day. It is not unusual to find amusement park water spray features with interactive fountains that have more users coming into contact with the water than number of gallons of water in the water feature. These same pools often have problems reaching breakpoint or keeping chloramines within acceptable levels.

If a chloramine residual persists in a pool in spite of the operator following proper breakpoint chlorination techniques, and continues to be a chronic nuisance, some of the following suggestions should be tried.

Regular Dilution

Drain and replace with 30 liters (approximately 8 gallons) of fresh water per user per day, as recommended in the German DIN (Deutsch Industrie Normen) Standard 19,643: “Treatment & Disinfection of Swimming & Bathing Pool Water”. The DIN Standard has been adopted by the European Community, and FINA requires water standards compatible with the DIN standard during international swimming competition.

Increase Exposure Time and Chlorine Concentration

You may be successful in reaching breakpoint by superchlorinating for longer periods of time with higher levels of chlorine.

Draw Water from the Pool Surface

Chloramines are concentrated near the surface of the water, as are most organic contaminants. During breakpoint chlorination, turn off the valve which draws water from the main drains and direct all the water through the perimeter overflow system. By circulating only through the skimmers or gutters, you will speed up the process by removing the water where chloramines are concentrated first.

GAC Filtration

Install secondary granulated activated carbon (GAC) filters and remove ammonia through filtration. GAC filters can be used to treat a slip–stream of water continually drawn off the main effluent line, or to treat source water prior to its being added to the pool. Many pools in areas of the country where municipal water utilities are adding ammonia to the source water to prevent trihalomethane formation in drinking water are installing GAC filters to pre–treat fill water to keep ammonia levels below 0.02 ppm. Chloramination has become a common practice by water utilities in order to comply with U.S. EPA water quality standards for drinking water to prevent formation of chloroform, a known carcinogen. Since chloramines do not react with raw water organic precursors which form when vegetation decays, monochloramines are commonly being used to treat water which has been stored in reservoirs. This practice is causing havoc in swimming pools.

Non Chlorine Oxidizers

Potassium peroxymonosulfate (AKA: monopersulfate), can be used instead of chlorine to shock , or oxidize chloramines and other organic contaminants from the water. The product is a buffered chemical compound which utilizes oxygen to prevent or destroy the eye irritation and odor qualities of pool water by reacting with ammonia to produce chloride and nitrogen. Sold under various trade or brand names, the product has be successfully marketed to homeowners, and is beginning to make inroads into the commercial pool market.

Unlike chlorine which must reach a “breakpoint”, any amount of potassium peroxymonosulfate added to water will oxidize some material. Normally though, between 5 ounces and one pound per ten thousand gallons of water is added on a weekly basis to pools, and daily basis to spas. Non chlorine oxidizers will not raise chlorine levels, are totally soluble, do not cause bleaching, and they don’t affect water balance or pH. Monopersulfates are especially recommended for pools or spas with high bather load to water volume ratios where total dissolved solids and ammonia normally build–up at a rapid pace.

The pool owner should be cautioned however, that regular use of non chlorine oxidizers may irritate bathers causing them to itch. Also, potassium peroxymonosulfate is known to have an effect on DPD reagents in both liquid and tablet form, causing water samples to turn dark red, and may cause a false high free available chlorine reading. DPD reagent #3 is oxidized by monopersulfate so the test actually reads the monopersulfate residual preventing an accurate reading which distinguished between free and total chlorine. Some test kit manufacturers sell FAS–DPD reagents that eliminate monopersulfate interference.

Some pools maintain a residual of monopersulfate to help eliminate bather waste and the build–up of organic contaminants, as a preventative rather than corrective treatment. One manufacturer (U.S. Filter) has patented a continuous breakpoint halogenation and peroxygenation system. Potassium peroxymonosulfate doesn’t react with chlorine, but rather oxidizes contaminants and reduces the demand on the sanitizer. It should be noted though that not all products sold as non chlorine oxidizers contain the active ingredient potassium monopersulfate. For example, sodium percarbonate (AKA: sodium carbonate peroxyhydrate) releases or produced hydrogen peroxide, and reacts with chlorine.

Eliminate the Chlorine to Eliminate the Chloramines

Hydrogen peroxide or sodium thiosulfate can be added to the pool to drop the chlorine level to zero. This eliminates the free chlorine residual by converting chlorine back to chlorine salt. When chlorine is eliminated from the water, chloramines will also be eliminated. However, when chlorine is reintroduced, it will start combining with the ammonia which is still present in the water and form chloramines, but hopefully in a gradual manner and as a less objectionable monochloramine rather than nitrogen trichloride.

A word or two of caution – don’t overdo the amount of hydrogen peroxide or sodium thiosulfate you add to the water or you will create a chlorine demand and have a difficult time reestablishing a chlorine residual. Also, do not add products containing hydrogen peroxide to a pool which utilizes diatomaceous earth filters, since hydrogen peroxide reacts with and dissolves D.E.

Zeolites

Zeolites with a high (at least 80%) percentage of clinoptilolite can be used as a filter media instead of #20 silica sand in sand filters. Zeolites are a family of granular, extremely porous volcanic minerals capable of removing ammonia from the water as well as particles down to 5 microns in size, equivalent to the filtering capabilities of a diatomaceous earth filter. Zeolites for swimming pool filtration are marketed under various trade names by Neptune Benson (Clinopure 80), British Zeolite Co. (Zeoclere–30), Innovative Water Science (Zeo–Pure 90), Eco Smarte (Hydroxite #2), and others.

When a layer of 10% sodium chloride (table salt) is added to the filter bed an ionic reaction occurs which causes the absorption and removal of ammonia as the water passes through the filter, thereby reducing chloramine formation. The pool operator must regenerate filter media every 6 months by backwashing, shocking with a salt solution, allowing the bed to reactivate for 24 hours, agitating the media, then backwashing. Zeolites supplied by a reputable distributor should have a life expectancy 5 to 7 years.

Corona Discharge Ozone Systems

Organic contaminants are slightly reactive with ozone, but after being partially oxidized, microflocculation allows their removal by filtration. Inorganic contaminants such as ammonia react significantly with ozone when the pH is maintained below 9.0. Ozone constantly oxidizes monochloramines to form chloride and nitrate ions. Unfortunately, ozone also destroys high free chlorine residuals in the process of destroying chloramines, so chlorine lost in the process must be constantly replaced.

Ultraviolet Light

UV light whether from natural sunlight or from UV light sanitation systems can be used to destroy chloramines and aerosolized chlorine compounds. If natural sunlight cannot be brought into the natatorium, UV light sanitation systems can be installed to provide supplemental sanitation and destroy chloramines.

UV light systems are installed in–line and are used in combination with either hydrogen peroxide or chlorine which provides a residual sanitizer and oxidizer in the pool water. The system consists of a treatment chamber installed on the filter effluent line, control box and power supply. Photolytic liners are permanently attached to the internal surfaces of the treatment chamber. Water flows through clear, quartz glass or Teflon tubes through the treatment chamber, passes the UV lamps (arc tubes) and pathogens are destroyed. UV kills microorganisms by destroying the DNA in the cells. There is no change in water color, temperature, taste, pH or chemical composition, however, turbid water will absorb UV light and make UV less effective as a disinfectant.

Disinfectant level is related to light intensity and exposure time. UV dosage is measured in either microwatt seconds per square centimeter (MWS/cm2). You may also see intensity and exposure time expressed in millijoules per square centimeter (mJ/cm2) instead. Six thousand to 10,000 MWS/cm2 or a minimum of 60 mJ/cm2are needed to destroy pathogenic organisms.

There are two types of UV lamps: low pressure (with an electromagnetic spectrum between 185 and 254 nanometers); and more commonly used today, medium pressure high intensity (with a wider electromagnetic spectrum between 180 and 400 nanometers, and not affected by water temperature). UV is most germicidal in wavelengths between 240 and 280 nanometers. Organic compounds are best photo oxidized by hydroxyl radicals in wavelengths below 230 nanometers. The bond between chlorine and nitrogen is broken, and chloramine destruction is most effective in the range of 245 and 340 nanometers, making low pressure bulbs a poor choice for chloramine destruction.

Increase Airflow Over the Water Surface

It is not possible to superchlorinate below a pool blanket or inside an enclosed pipe. By definition, oxygen is needed for oxidation to occur and off gassing into the air must take place. If there isn’t enough oxygen over the pool, breakpoint will not be achieved. Think of a fire. If the fuel is present but oxygen is lacking, combustion will not occur. Do whatever you can to get more air moving over the pool. So open the windows and doors, turn on the exhaust fans to move large volumes of air.

Unfortunately, as you speed up the removal of chloramines from the water, you release them into the air in the natatorium. Since like an outdoor pool, you do not have the ever present wind to blow away the odors and irritants, the air handling system must be designed to take the place of nature.

Chloramines are very volatile and easily vaporized into the air surrounding the pool. You can reduce the chloramine concentration in the air, by increasing the percentage of outside air brought into the natatorium and diluting the objectionable chloramine odors and irritants with fresh air. There should be at least 8 complete air exchanges per hour. Open air dampers to permit 100% fresh air to be brought in especially during breakpoint chlorination. During regular operation, as little as 15% fresh air may be permitted by code, but a minimum of 40% is recommended (up to 100%) depending on usage patterns, natatorium design, and equipment installed. For instance, pools that have water features installed that agitate water or aerosolize water vapor, particulates, or pathogenic organisms should exchange more air.

The location and placement of supply registers and return/exhaust ducts should be such that air is supplied low, moved across the water surface at a velocity less than 25 feet per minute to move the heavier than air gasses concentrated and settled directly over the pool, and exhausted high near ceiling level. Pollutants travel from positive to negative pressure areas, so natatoriums should be positively pressured in relation to the out of doors, and negatively pressured in relation to surrounding occupied spaces.

The air handling system installed should be capable of providing thermal environmental temperatures acceptable to 80% or more of the primary/priority facility users, averting sick building syndrome problems, and preventing discernible odors, without evident drafts, stratification of air, thermoclines or temperature gradients.

Download Pool Tip #52: Recommended Pool Chemical & Natatorium Air Levels (PDF format, 44KB)