OPERATIONAL STANDARDS FOR SWIMMING POOLS. Fargo Cass Public Health rd Ave N Fargo North Dakota /26/09

Transcription

1 OPERATIONAL STANDARDS FOR SWIMMING POOLS Fargo Cass Public Health rd Ave N Fargo North Dakota /26/09

2 TABLE OF CONTENTS FORWARD...1 Chapter 1 - Laws and Regulations Maintenance and Operation of Public Water Works Systems, Swimming Pools, and Sewage Systems; Regulation by Health Department Submission of Construction Plans and Specifications Required Approval of Construction Plans and Specifications Inspection of Swimming Pools...2 A. Pool Facilities in Fargo, North Dakota...3 Chapter 2 - Operational Practices Bacterial Testing Keeping Records Personnel Bathhouse Footbaths Showers Regulations Pool Safety...6 Chapter 3 Water Chemistry ph Adjusting ph Alkalinity Adjusting Alkalinity Hardness Adjusting Hardness...9 Chapter 4 Disinfection Chlorine Chlorine Gas Calcium Hypochlorite Sodium Hypochlorite Stabilizer Bromine Ozone Ultraviolet Iodine...16 Chapter 5 Recirculation System Hair and Lint Strainer Pumps...17 i

3 5.3 Sand filters High-Rate Sand Filters Diatomaceous Earth Filters Cartridge Filters Length of Operation...23 Chapter 6 Special Conditions Swimming Pool Start-up Pool Temperature Wind Protection Pool Bottom Surface Film Hard Water Scale Iron Removal Organic Color Cloudy Water Algae Control Insects Painting...28 Chapter 7 Special Pools Wading Pools Spas Natural Bathing Areas...31 Appendix Off Season Protection Pool Loading Indoor & Outdoor Pools Chemical Dosage Superchlorination Chlorinator Settings Safety Rules for Gas Chlorine Equipment Dechlorination Testing Chlorine Residuals Testing ph Bacteriological Testing Enclosure for Swimming Pool Chlorinators Injector Location for Vacuum-Operated Chlorinators Recommended Swimming Pool Operations Standards...44 ii

4 FORWARD This manual has been prepared to aid swimming pool operators, design engineers, and other interested persons in the construction and operation of a swimming pool following good public health practices. Proper swimming pool design and operation protects the bather against: 1. Infections transmitted through the pool. 2. Infections transmitted through the bathhouse facilities. 3. Physical injury within and about the pool. Definite epidemiological evidence has been recorded to show transmission of infectious diseases through pool waters. Definite proof of the transmission of eye infections, impetigo, etc. through the common bathroom is also known. Dermatitis, such as athlete s foot, is commonly transmitted in bathing facilities. The primary responsibility of the swimming pool manager is to provide clean, healthful recreation. Rules must be understood and followed. Only safe equipment should be brought into the pool environment. Another responsibility of the pool operator or owner is that of protection against physical injury within and about the pool area. The attendants should have full charge of the bathing facilities and have the authority to enforce rules of safety and sanitation. Only qualified lifeguards should be employed. We believe that if the operational practices outlined in this manual are observed, your swimming pool can serve as a healthful source of recreation. 1

5 CHAPTER 1 - LAWS AND REGULATIONS 1.1 Maintenance and Operation of Public Water Works Systems, Swimming Pools, and Sewage Systems; Regulation by Health Department. For the protection of public health and the prevention of pollution of waters, all public water works systems, swimming pools, and sewage systems shall be maintained and operated in accordance with applicable public health standards, codes, and regulations. The health department, and agents and employees thereof, shall have authority to regulate the public health and safety in the city of Fargo concerning use, design, operation, and maintenance of swimming and wading pools and shall have such authority to adopt regulations, rules, standards and practices. Such regulations, rules, standards, and practices shall be approved by the board of city commissioners, are hereby adopted by reference and fully incorporated herein, including any amendments hereinafter adopted, and shall be controlling within the jurisdiction of the health department. Fargo Municipal Code Submission of Construction Plans and Specifications Required. Before work or construction is commenced on any water works system, sewage system, or public or semi-public swimming pool, or for any alteration, addition, remodeling or other improvement thereof, the plans specifications, and any other pertinent information shall be submitted to FARGO CASS PUBLIC HEALTH for review prior to construction. Residential swimming pools are exempt from this requirement, but must meet fencing requirements and other design standards adopted by the health department and approved by the board of city commissioners. 1.3 Approval of Construction Plans and Specifications. Plans and specifications reviewed by FARGO CASS PUBLIC HEALTH will be approved only when such plans and specifications fully meet and comply with existing statutes, local rules, and applicable sanitary standards. Plans and specifications upon which approval is being withheld will be returned with the reasons for withholding approval. 1.4 Inspection of Swimming Pools. The health department may inspect or cause to be inspected all public or semi-public swimming pools and family residential pools within the city at such times as it may deem necessary to carry out the intent of this ordinance. The health department is hereby authorized to enter upon any premises, private or public, to take such samples of water from such pools at such times as it may deem necessary and to require the owner, proprietor or operator to comply with rules and regulations pertaining to swimming pools promulgated by the health department in accordance with this ordinance., and as approved by the board of Fargo city commissioners. In the event of the failure of compliance after due notice with the rules and regulations and requirements of the health department or the requirements of this ordinance, the health department shall have the power to abate or cause a suspension of the use of such public or semi-public swimming pool or family residential pool until such time as the same is, in the opinion of the health department, no longer a menace or a hazard to health, safety or morals. 2

6 A. POOL FACILITIES IN FARGO, NORTH DAKOTA All public and semi-public pool facilities are also required to adhere to the rule as set forth in Article of the Fargo Municipal Code. The primary aim of these rules is to regulate the water quality and record keeping practices of public and semi-public pool facilities. Following is a brief synopsis of the rules: (i) (ii) (iii) (iv) Routine Bacteriological Sampling: The owner or operator is required to sample the microbiological water quality of the pool facility at least once per week for public pools and once monthly for semi-public pools. Public pool facilities, which are open for a full year, may substitute 50 percent of the required microbiological water samples with ph and free chlorine residual test results. Record Maintenance: The owner or operator of a pool facility shall maintain records of microbiological analysis, all pool related correspondence, plus documentation of daily operation and maintenance practices for a minimum of 3 years. Turbidity/Clarity Requirements: Swimming pool water must have sufficient clarity at all times so that the main drain or drains located at the deep end of the pool are clearly visible from the pool decking. Disinfectant Residual: All pool facilities shall disinfect the pool water by continuous chlorination or other means or methods of equal bactericidal efficiency. A minimum of free chlorine residual of 1.0 milligrams per liter (mg/l) or a department approved halogen or compounds of them, imparting an equivalent disinfecting residual must be maintained in the water at all times. 3

7 2.1 BACTERIAL TESTING CHAPTER 2 - OPERATIONAL PRACTICES All public and semi-public pool facilities must meet microbiological water quality requirements. To meet these requirements, a microbiological water sample must be collected once weekly from public and once monthly from semipublic pool facilities during their period of operation. A satisfactory sample is one that does not show greater than 200 bacterial colonies per one milliliter of sample and does not show the presence of the coliform group in a fermentation tube or membrane filter test. All samples must be submitted to a laboratory which has been certified by this department. 2.2 KEEPING RECORDS Fargo Cass Public Health requires that a daily operational log of the pool is kept. Results must be recorded twice a day for public pools and once a day for semi-public pools. This is of great value as a source of information for the pool operator, as an assurance to responsible officials and the public that proper health and safety standards are being followed, and as a reference for future operation of the pool facilities. 2.3 PERSONNEL Sufficiently trained personnel should be available to accomplish effective pool management, bathhouse supervision, lifeguarding, and maintenance of filtration and re-circulation systems. We recommend that a permanent employee of the City or Park Board be assigned to maintain the mechanical equipment. An adequate number of lifeguards are essential. Many authorities feel that at least one lifeguard should be provided for every 75 swimmers. Roving lifeguards, in addition to those on duty in the lifeguard chairs are desirable. The use of water safety aides to assist lifeguards in controlling patrons during periods of heavy loading could markedly increase in efficiency. These aides are generally responsible high school students who show an interest in pool activities. Pools operating on limited budgets may use aides and compensate the aides with free swimming. There is no substitute for qualified lifeguards but, under certain circumstances, water safety aides may help prevent a dangerous situation. The manager s responsibility does not cease when the swimming period is over. The swimming pool is an attractive nuisance and may be very dangerous if accessible when not officially in use. Using the pool facilities without supervision must not be permitted. 4

8 2.4 BATHHOUSE The first contact the public has with the pool is the bathhouse and their opinion of the entire facility will be based on what they see here. Good housekeeping is essential and results in a clean appearance that will greatly promote the swimming pool program. The bathhouse should be adequately lighted and ventilated. Lavatories and toilets should be cleaned and disinfected twice daily if odors and unsightliness are to be avoided. Adequate waste receptacles should be provided. Clean floors are especially important. Contact with the dressing room floors, shower stalls, and other places where the fungus might live, frequently transmit athlete s foot and other fungal infections. In most pools, fungal infections may be controlled by a daily scrubbing with hot, soapy water followed by liberal applications of a chlorine solution (1/4 to 1%). 2.5 FOOTBATHS Footbaths for the control of athlete s food have been known to promote the growth of bacteria and shall be eliminated. 2.6 SHOWERS As a further aid in preventing the spread of disease, every effort should be made to inspect all patrons and exclude those showing symptoms of infection. Before entering the pool, hot water and soap shall be provided and nude bathing shall be required. This removes much of the perspiration, mucus, and bacteria from the swimmer s body that otherwise would be washed off in the pool. Some authorities state that permitting the public to swim without bathing reduces the efficiency of the disinfecting system by as much as 50%. It is important to remember at this point that good house keeping, along with a thorough cleansing of the bather before entering the pool, will eliminate many of the operational difficulties that often develop. 2.7 REGULATIONS The following regulations should be enforced to assure the sanitation and purity of the pool. A. Refuse admission to all persons having any contagious disease or infectious condition such as a cold, ringworm, foot infections, etc. Also, exclude those persons with excessive sunburn, corn plasters, adhesive tape, or bandages of any kind. B. Do not allow suntan ointments, food, gum, or tobacco in the pool area. C. Require nude showers before entering the pool. D. Glassware and similar material with a tendency to shatter on impact is not allowed in pool area. E. Unnecessary spouting of water, roughness, or rowdiness shall be prohibited in the pool area. F. Domestic animals are not permitted in pool area. 5

9 G. Diving is not permitted except in designated area. H. All diaper age children must wear waterproof diapers. 2.8 POOL SAFETY About 80% of all accidents at the pool are the result of falls, which can be caused by walk defects such as poor drainage, slippery surfaces, and steps. Pooling of water in low spots is the most common reason for walk accidents. If the water stands and is not swept away, it will collect dirt and algae, creating a slippery condition. This water is also a source of bacterial contamination if carried into the swimming pool. It is good practice to scrub and disinfect walkways in the same manner that is used for dressing rooms. Broken walks are a source of cuts and bruises. Cracks, broken sidewalks and walk areas shall be patched and properly pitched to drain away from the pool. A pool surface area of about 300 square feet around each diving board shall be restricted for diving only, as injuries have occurred when divers have collided with each other. If the diving bay dimensions or water depth is limited, the heights of the diving boards shall be restricted to reduce the chances of injuries caused by divers colliding with the pool bottom or sides. Fatalities have occurred while swimming alone or when accidentally falling into a pool that is either empty or inadequately supervised. Motel and private club pools are a special safety hazard. Many of these pools do not have locked protective fences or barriers to control access. These pools become attractive nuisances and are a hazard to both children and adults. Doors to all indoor pools should be kept locked when adequate supervision is not provided. Fences or barriers shall protect outdoor pools. 6

10 CHAPTER 3 - WATER CHEMISTRY A swimming pool, like a lake or stream, is subject to constant pollution, making it difficult to maintain the water purity at all times. Wind blown dust and dirt, perspiration, mucus, and bacteria from swimmers bodies are all dissolved by the water, providing an ideal nutrient for the growth of various microorganisms. These substances cause changes in the physical and chemical condition of the water, stimulating the growth of bacteria and algae. Lack of vigilance on the part of the pool operator can cause massive bacterial and algal growths, resulting in high water turbidities and subsequent closing down of the swimming pool facility. 3.1 ph There is a precise scientific definition for ph, of course, but for pool operators it is sufficient to state that ph is simply a numerical scale representing a condition of pool water. It represents the degree to which water is acidic or basic. The scale ranges from 0 to 14, with the midpoint, 7, representing the neutral condition neither acidic nor basic. The scale moves from this neutral condition at 7 upward to 14, representing an increasingly more basic or alkaline state. Below 7 the scale represents more acidity, with the lower numbers representing a more strongly acidic condition. For example a ph of 4 is more acidic than a ph of 6. The ph of pool water varies with mineral content and may require a chemical analysis to determine the optimum ph for stability to prevent scale or corrosion from occurring. It is important that the pool water be kept on the alkaline side at all times. Therefore, a ph range of 7.2 to 7.8 is recommended. Neglect on the part of the pool operator to check and adjust the ph will create operational problems should the ph fall outside the recommended limits. Some problems that may occur with an improper ph are: (a) Irritation to eye and mucous membranes of the bathers. (b) Unstable chlorine residuals. (c) Corrosion or scaling problems. (d) Turbidity problems caused by chemical imbalance. Body acids introduced by bathers and the addition of gas chlorine are the major reasons for the ph to drop. The ph will rise with the addition of calcium, hypochlorite, sodium hypochlorite, and soda ash. Since chlorine and bathers are a normal part of the operation of swimming pools, it can be seen that adjustment of the ph must be done daily. 3.2 ADJUSTING ph Adding soda ash (sodium carbonate) normally does raise the ph. Soda ash is available as a powder in 100-lb bags. When added to water, soda ash combines with carbon dioxide producing sodium bicarbonate, the desired type of alkalinity. 7

11 Soda ash should be applied with a solution pump capable of feeding accurate amounts of soda ash solution. About 1.2 lbs. of soda ash is necessary for each pound of chlorine gas to maintain a constant ph and to prevent the water from becoming corrosive. It is false economy to shorten the life of the equipment by the small savings realized from insufficient use of soda ash. Adding muriatic acid (a commercial name for hydrochloric acid) normally does lower the ph, which often must be done when calcium hypochlorite or sodium hypochlorite is used as the disinfectant. The ph may also be lowered using a dilute from of sulfuric acid (40% strength) or sodium bisulfate. Sodium bisulfate is a dry form of acid, milder than the liquid types and much safer to handle, but more expensive. Severe damage has occurred to pool equipment when operators have added the acid without first diluting it. Dilute the acid at least 2 to 1 before adding it to the pool. To prevent splattering, always add the acid to the water. NEVER ADD WATER TO ACID. 3.3 ALKALINITY Pool operators are seldom aware of alkalinity or, more specifically, bicarbonate alkalinity. Few test kits sold to operators are equipped for checking alkalinity, yet a pool with no alkalinity would be completely unmanageable, as the ph would rapidly fluctuate. Maintaining the proper alkalinity will provide a buffer against rapid ph changes that could occur with changes in bather loads or chemical feed rates. The recommended alkalinity of a swimming pool is between 100 and 150 mg/l. For pools using hypochlorite solutions, the alkalinity should be maintained slightly lower, at about 70 to 80 mg/l, as the hypochlorite solutions add alkalinity. 3.4 ADJUSTING ALKALINITY Some pool operators have difficulty in maintaining the ph low enough even though they discontinue the use of soda ash. These pools usually have make-up water of high alkalinity and/or may use hypochlorite solutions which add to the alkalinity of the water. Feeding muriatic acid or a solution of sodium bisulfate may control excessive alkalinity. Waters of excessive alkalinity and high ph, common in western North Dakota, may precipitate dissolved minerals such as calcium, magnesium, iron, and manganese, resulting in considerable pool turbidity. Such waters require the addition of large quantities of acid for stabilization. The addition of 1.5 pints of muriatic acid per 10,000 gallons of water will lower the total alkalinity by 10 mg/l. The acid will lower the ph to the recommended level, but may not be in an amount sufficient to neutralize the excessive alkalinity. When this condition occurs, the ph may rise to near the original level in a relatively short time. Additional acid must be added at intervals until the ph finally stabilizes within the desired range. 8

12 Pools with low alkalinity may be adjusted upwards with the addition of sodium bicarbonate. The addition of 1.5 lbs. of sodium bicarbonate per 10,000 gallons of water will raise the total alkalinity by 10 mg/l. If the ph needs adjustment upward, then soda ash may be used to increase both the alkalinity and the ph. 3.5 HARDNESS Hardness in swimming pools consists mainly of the dissolved salts of calcium and magnesium. Hardness is generally not a problem when the total alkalinity and ph are kept within limits. Therefore, testing for hardness and adjusting the level are not necessary after the initial filling of the pool. Very soft waters may be turbid and may have to be adjusted to at least 150 ppm total hardness to obtain clarity. 3.6 ADJUSTING HARDNESS The total hardness may be increased without an increase in alkalinity by adding calcium chloride. A dosage of 0.2 lbs. of calcium chloride in 25,000 gallons of water will increase the hardness by 1 ppm. Additional calcium chloride may have to be added from time to time depending upon the amount of make-up water added. Use this procedure only with waters of low hardness and high alkalinity because it can increase the corrosive tendency of the water. 9

13 CHAPTER 4 - DISINFECTION Swimming pools receive all manners of dirt and debris and it is essential that some form of disinfectant be used to destroy any potentially dangerous organisms. To do this, swimming pool disinfectants must possess certain properties. Above all others, they must be effective and must be capable of rapidly killing bacteria. They must have residual properties such that they maintain a presence in the water to eliminate bacteria and harmful organisms as they enter the pool. A disinfectant must be safe and harmless to bathers. It should not create undesirable conditions in the pool. It must be readily available, inexpensive, easily stored and handled, and it should possess algaecidal properties. 4.1 CHLORINE The most common means of swimming pool disinfection is through the application of chlorine. Chlorinating of pool water will provide for disinfection to kill bacteria and diseaseproducing microorganisms, which might infect bathers and oxidation (to react with and destroy other contaminants such as algae, body oil, minerals, dust, and other materials, which cause color, odor, and turbidity). The advantages of using chlorine as a swimming pool disinfectant are: A. Chlorine is effective. It possesses both bactericidal and algaecidal properties. B. It is easy to store and handle. C. It is available in a variety of forms such as a gas, liquid, or solid. D. It can be dispensed by hand or automatically through a wide variety of devices. E. Its presence in water is easily detected and measured. F. It is widely available and relatively inexpensive. When chlorine, in any form, is added to water a chemical reaction takes place with the resulting formation of hypochlorous acid. This is the chemical agent which reacts with and destroys bacteria and other undesirable contaminants in pool water. The amount of hypochlorous acid, which is produced by this reaction, is dependent on the ph of the water. Therefore, maintaining the ph within the proper range will also aid in establishing and maintaining an adequate and effective chlorine residual. Chlorine is a very active chemical. As it is added to the water, it will react with many substances both dissolved and suspended in the water in the following ways: (pg 13, fig 1). 10

14 A. CHLORINE DEMAND: Swimming pools are reservoirs open to contamination for all manners of dirt and debris. Bathers, rain, wind, and chemicals can also contribute impurities to the water. When chlorine is added to a pool, it immediately reacts with and begins to destroy some of this foreign matter. The amount of chlorine required to react completely with these chlorine-destroying compounds is termed the chlorine demand. Also related to chlorine demand is the amount of chlorine required to kill the bacteria and other microorganisms present in the water. Sufficient chlorine must be added to the pool water to satisfy its chlorine demand, in addition to the amount required to maintain an adequate residual. B. COMBINED CHLORINE RESIDUAL: As more chlorine is added to the water, it will react with any dissolved ammonia present to produce combined chlorine (chloramines). These products are odorous, irritating to the eyes and mucous membranes and are weak disinfectants. C. BREAKPOINT: Further addition of chlorine will oxidize the previously formed chloramines and cause the combined chlorine residual to be reduced to almost zero. As reaction of all chloramines nears completion, additional chlorine will be retained in the water as a residual and will be available to act on bacteria, which may be subsequently introduced into the pool water. This point on the curve is referred to as the break point. D. FREE CHLORINE RESIDUAL: Residual chlorine exists after break point as free chlorine (hypochlorous acid), which is a strong disinfectant. This is the desired area on the curve due to the nearly complete oxidation of all bacteria and contaminants and the presence of a strong disinfectant in the form of free chlorine. To insure that adequate disinfecting is taking place, it is a requirement under Fargo Municipal Code that a minimum free chlorine residual of 1.0 ppm be maintained at all times. Various ammonia and nitrogen products may enter the pool through wind blown plant life and perspiration and urine from bathers. Their levels can gradually build up until 11

15 a substantial amount of chloramines are being formed due to the reaction with the chlorine residual. This will cause the free chlorine residual to drop, thereby decreasing disinfection effectiveness, causing irritations to the eyes and mucous membranes, and producing associated odors. This undesirable condition can be avoided to a great degree by routinely super-chlorinating. Super-chlorination is the process of quickly raising the free chlorine residual 5.0 to 10.0 ppm and then allowing this higher residual to dissipate over night. Super-chlorination can be performed on an established schedule, for example, every two weeks or a test kit can be used to determine when it is necessary. If testing of the pool water shows an appreciable amount of combined chlorine (the difference between the total and free residuals), 0.2 ppm or more, then super-chlorination may be necessary. This method will be more economical and accurate than an established schedule, but either will work. Chlorination, as the term implies, is the practice of introducing chlorine to pool water. Regardless of the product used or the method of application, the goal is to achieve a chlorine residual possessing strong oxidizing and disinfecting properties. Chlorine may be supplied as a gas, a solid, or a liquid, each having different handling and safety conditions, but still providing chlorine for effective disinfection. 4.2 CHLORINE GAS Chlorine gas is packaged under pressure as a liquid in metal cylinders and is fed into the system by a chlorinator, which regulates the amount of gas which; is introduced. The cylinders are of seamless steel construction with an operating valve equipped with a safety device in the form of a fusible metal plug. These plugs are designed to melt at 158ºF to permit the escape of chlorine gas to prevent tank rupture. This fusible plug should not be tampered with under any circumstances. The valve on the chlorine cylinder has a non-standard pipe thread requiring a special wrench. The use of these non-standard connections is intended to discourage anyone from using pliers, wrenches, or hammers to force connections or otherwise depart from standard handling techniques. If you do not presently have one of these special wrenches, please obtain one from your chlorine supplier. The wrench must remain on the valves in use at all times. Always use a new lead washer when connecting a chlorine cylinder to the chlorinator. Open the valve only one-quarter to one-half turn after connecting the chlorinator and check the connection for the presence of leads. This may be accomplished by holding a swab moistened in ammonia near all the connections. The presence of chlorine gas will be indicated by the formation of a white smoke-like cloud of ammonium chloride. Do not force the chlorine cylinder valve if it is difficult to open. Damage to the valve may occur, causing a major chlorine leak. Return the cylinder to the supplier rather than risk the danger of a leak caused by a broken valve. The quantity of gas in a chlorine cylinder can be determined only by weighing the cylinder on a platform scale. When a new cylinder is connected to the chlorinator, its weight should 12

16 be noted. Daily loss of weight records will indicate the number of pounds of chlorine used during the previous day and will indicate when the cylinder is empty. Before removing the chlorine cylinder from the chlorinator, be sure the valve is closed and tested for leaks. Replace the valve hood. The empty tank should then be treated and handled as though full until it is removed from the premises. If a leak occurs, all persons should be cleared from the area and kept away until the cause of the leak is found and the trouble corrected. Any person overcome by, or exposed to chlorine should be moved at once to an uncontaminated area and should be kept completely at rest and warm until medical assistance can be obtained. If breathing has ceased, immediately apply artificial respiration or use approved inhalation equipment or oxygen. 4.3 CALCIUM HYPOCHLORITE Chlorine is also available as a granular powder or in solid tablets. The most common form of dry chlorine is calcium hypochlorite, which contains 65% available chlorine. Calcium hypochlorite is commonly used as a disinfecting agent for pool water, decks, dressing rooms, and equipment. It is safer material than chlorine gas with respect to handling and feeding, but it may present serious problems if spilled or scattered in a moist or wet environment or if oxidizable material is introduced to the container. Calcium hypochlorite can be manually fed directly into the pool from handheld containers to either facilitate super chlorination or as an alternative feed in the event of equipment failure. Normally, however, it is mixed with water in tanks and the clear liquid is fed to the recirculation system by means of mechanical feeders or hypo chlorinator. A heavy precipitate of calcium carbonate forms when calcium hypochlorite is dissolved in water, so this must be allowed to settle and the clear liquid siphoned off the top. When calcium hypochlorite is used as a source of chlorine for public swimming pools, it is recommended that the chemical be fed continuously by means of a chemical feeder. Calcium hypochlorite is often used for chlorination of small private and semi-public swimming pools. Several methods may be used for applying this chemical. A. Granular calcium hypochlorite can be broadcast over the surface of the pool water. B. A solution of calcium hypochlorite can be poured on top of the water. C. A stock solution may be fed continuously by means of a diaphragm typeproportioning pump. Calcium hypochlorite is a powerful oxidizing agent and the hazards attributed to this product are directly related to its oxidizing power. Calcium hypochlorite may be used with safety if the following precautions are followed: A. Always keep calcium hypochlorite in its original container and store in a cool, dry place away from oils, rags, and other combustible organic materials. B. Use only a clean, dry, non-combustible scoop when handling the powder. C. Never mix calcium hypochlorite with other chemicals. 13

17 D. Always pour calcium hypochlorite into the water when making a solution. E. Wash hands immediately after handling. F. Clean up any spilled material immediately by flushing down a drain. G. Avoid inhaling the calcium hypochlorite dust. H. Read and follow directions on the label of the container. 4.4 SODIUM HYPOCHLORITE Sodium hypochlorite is a liquid compound (5.25 to 6% available chlorine) sold as a household bleach. In a commercial form it may be obtained in strengths up to 10% available chlorine and is usually purchased in one gallon jugs, five gallon carboys, or 55 gallon drums. 4.5 STABILIZER Cyanuric acid, or simply stabilizer, is a chlorine-extending compound. It reportedly helps chlorine resist the deteriorating effects of ultraviolet light (sunlight). One serious drawback in using chlorine has been its susceptibility to the weakening effects of sunlight, especially in outdoor pools. Cyanuric acid acts as a shield, protecting the free chlorine residual from these effects and extending its useful life. Cyanuric acid stabilizer is a semi-permanent additive. Losses from the pool usually occur from splash out and drag out into the deck area, filter backwash, vacuuming to waste and leakage. In other words, when water is physically removed from the pool, the stabilizer goes with it. Assuming that the pool does not leak, stabilizer losses will be very small on a day to day basis. One serious drawback to the use of cyanuric acid is that it reduces the effectiveness of the chlorine residual. A stabilized free chlorine residual is only about 40% as effective as an equivalent value of free chlorine with no cyanuric acid present. This means that to obtain equivalent disinfecting action, the stabilized free chlorine residual would have to be two and one half times greater (at least 2.5 ppm) than a free chlorine residual without cyanuric acid stabilization. Some chlorine compounds already contain cyanuric acid and are known as chlorinated isocynaurates, cyanurates, or stabilized chlorine. They contain 60% available chlorine and are designed to do two jobs at once. While killing bacteria and algae, they also add a measured quantity of stabilizer sufficient to maintain an effective level. The danger of using these chemicals as the only disinfecting agent is the gradual buildup of cyanuric acid (which is toxic at high concentrations) in the pool water over an extended time. Whey the cyanuric acid level exceeds the maximum value; it may be reduced only by diluting the pool water with water that is free of cyanuric acid. It is certainly not necessary to use the chlorinated isocynaurates to stabilize the pool. Stabilizer may be purchased as cyanuric acid, a whit granular powder. At the time of pool start up, it may be added slowly through the skimmer and in sufficient quantity to achieve a 14

18 residual of between 30 and 100 ppm. Consider 40 ppm as the ideal level. Follow the directions on the package for adding the recommended quantity to reach the ideal level. 4.6 BROMINE A dry bromine compound containing about 66% bromine is normally used for swimming pools. It has reduced the danger involved in handling bromine chemicals to a risk similar to that experienced with dry chlorine. Bromine is more expensive than chlorine and its bactericidal effectiveness is slightly less. The bromines primary advantage is that it is less affected by ph than chlorine. When combined with organic materials, perspiration, urine, etc., the compounds which form the bromamines have disinfecting capabilities similar to free bromine. These compounds are also less irritating to the eyes and mucous membranes than are chloramines. One further advantage of bromine is that it remains fairly stable in pool water as the temperature rises. Since spas and hot tubs maintain water temperatures higher than those normally found in swimming pools, bromine could be used in these cases. A disadvantage of using bromine is that the ph must be maintained in a range of 7.0 to 7.4, which increases corrosion problems. Bromine levels should be kept between 1.0 and 3.0 ppm. A chlorine test kit may be used to measure these values, but the reading obtained must be multiplied by 2.25 to obtain the actual bromine level in the water. 4.7 OZONE Ozone has proven itself over the years as a powerful disinfectant and oxidizer in treating drinking water. It is expensive to generate, toxic, corrosive, and does not leave a disinfecting residual. For these reasons, ozone is not a suitable disinfectant for pool use. Should ozone be used, another disinfectant such as chlorine, maintained at a proper level, must be used to provide a constant disinfecting residual. Ozone equipment should be located in a separate room. Even minor leaks could severely damage the pool equipment, as ozone is extremely corrosive. Careful monitoring of the ozone levels must be made to insure that ozone is not present in the pool area especially in indoor pools, as ozone is also toxic. 4.8 ULTRAVIOLET Ultraviolet radiation has been used to disinfect water supplies but, like ozone, does not leave a disinfecting residual. Also, the water must be completely free of turbidity because ultraviolet radiation has limited powers of penetration into water. Should ultraviolet radiation be used, chlorine or another disinfectant maintained at the proper level, must be used to provide a constant disinfecting residual. 15

19 4.9 IODINE Iodine is an effective bactericide for swimming pool use. Iodine residuals have normally been obtained through the chemical reaction of an iodine compound such as potassium iodide and chlorine. Iodine produces a long lasting residual, making it a good choice for decks and dressing rooms. The use of iodine produces a characteristic iodine odor in the pool area and causes the water to take on a yellow-green color (for aesthetic purposes, a high level of ph is desired to prevent water discoloration). Iodine has been more expensive to use as compared to chlorine. This, coupled with the odor and color problems, has all but eliminated the use of iodine in swimming pools. Iodine levels may be measured with a chlorine test kit by multiplying the reading by

20 CHAPTER 5 - RECIRCULATION A re-circulating type of pool has the necessary equipment to keep the water continuously clean and disinfected. Water is drawn from the pool through a hair and lint strainer by means of a centrifugal pump and then to the filters for removal of fine suspended material. After filtration, the finished water is returned to the pool through the inlets. This round trip the water takes is called the turnover rate. The capacity of the re-circulation system must be sufficient to provide one complete turnover of the pool water every six hours (1-hour for wading pools and 30 min for spa type pools). All of the water, however, does not go through the filters every six hours. The water that is filtered comes back to and mixes with the water in the pool and a portion of this water goes back through the filters. Continuous (24 hour per day) re-circulation reduces the amount of water that does not pass through the filters. Studies have indicated that a six-hour turnover rate will provide 95% to 98 % dilution of the pool water with filtered and chlorinated water. There will always be some water that does not get filtered and chlorinated, resulting in the survival of algae, bacteria and other organisms. 5.1 HAIR AND LINT STRAINER The hair and lint strainer located on the suction side of the pump is necessary to protect the pump impellers from damage or clogging by foreign material such as stones, leaves, lint, and hair. The strainer should be cleaned as often as necessary, but not less than once weekly, to prevent the loss of the pumps efficiency by the buildup of debris. Severe accumulation in the strainer will prevent sufficient flow of water to the pump and could cause cavitation, which will result in noise, vibration and erratic performance of the pump. Prolonged cavitation will result in serious damage to the pump impeller, bearings, and seal. Two strainers should be provided so that a clean one is available for immediate replacement. The wing nuts on the strainer bowl cover should also be firmly tightened to prevent air leaks. 5.2 PUMPS The heart of the re-circulation system is pump. It draws water from the pool, forces it through the filter and returns it to the pool. Single stage centrifugal pumps are commonly used due to their low cost and maintenance. The pump, and particularly the motor, should be protected against excessive moisture and chemicals. The floor of the pump room should be equipped with a drain and adequate ventilation should be provided at all times. The packing glands of centrifugal pumps are lubricated by a controlled leakage of water. The stuffing box gland nut should be adjusted to provide a leakage rate of several drops per minute. Most pool pumps are self-priming, but they should never be run dry. Even a short run on dry seals will injure them. Self-priming is accomplished by removing the cover from the pump strainer bowl and filling it with water. The pump will not self-prime unless the strainer bowl has water in it. 17

21 Centrifugal pumps, which are not self-priming, are primed by allowing the air on the suction side to escape through a bleeding valve or plug on the top of the pump casing. This allows the pump and impellers to be flooded on the suction side. Priming must be done with the pump not running to prevent damage to the water-lubricated packing rings. Lubrication of the ball bearings on the pump and motor should be done as prescribed in the manufacturer s instructions. Lime soap grease is often used as the lubricant. Care should be taken to prevent over lubrication, as this can result in heat damage to the bearing surfaces. Some of the more common operational difficulties encountered with pumps are: A. Failure to pump: This may be due to lack of priming, wrong direction of impeller rotation, or insufficient motor speed. B. Reduced pumping capacity: Probable causes are air leaks in the suction line, clogged hair and lint strainer, or closed valves. C. Mechanical trouble and noise: This may be caused by misalignment of the motor pump shaft, a bent shaft, damaged bearings, or improperly proportioned suction and discharge lines. D. Excessive leakage of water: The packing glands may need to be tightened or new packing rings installed. Any unusual operational problems with the motor should be noted and a qualified serviceman called for servicing. 5.3 SAND FILTERS Both gravity and pressure type sand filters are in use in North Dakota. For proper operation, sand filters should be equipped with a rate-of-flow indicator and loss-of-head gauges. Pressure filters should also be equipped with an air relief valve to prevent the filter from becoming air-bound. This valve should be opened at least daily to remove the air that collects in the top of the filter area. Care should be taken to see that automatic-type air relief valves are not sealed during the annual painting period. Its surface area determines the capacity of a sand filter. Sand filters are designed to operate at a filtration rate of from 2 to 3 gallons per minute per square foot of surface area. As the filter is used, an increase in loss-of-head or resistance to flow of water is noted. The freshly washed sand filter has some initial loss of head, usually about 2 feet, equal to a pressure of about one pound per square inch (psi). Gravity filters should be washed when the loss-of-head reaches from 7 to 9 feet. Pressure filters are generally back-washed when the loss-of-head reaches 5 to 7 psi. Cleaning of sand filters is accomplished by reversing the water flow and pumping it through the filter at a rate of 15 gallons per minute per square foot of filter area. This backwash should usually continue for 5 to 10 minutes. 18

22 An insufficient backwash rate will not thoroughly clean the sand bed and serious filter troubles may result. Cleaner filters and a saving on wash water may sometimes be obtained by breaking up or agitating the top of the sand layer before washing. After cleaning, a small amount of aluminum sulfate (alum) is usually added to the top of the filter bed for coagulation purposes. The alum reacts with the alkalinity in the water, producing aluminum hydroxide. Aluminum hydroxide is a sticky gelatinous substance, which clings to the sand particles and strains out the fine suspensions in the water. Care should be taken not to add too much alum, as an excess may add turbidity to the water. In most cases, 2 oz. of alum per square foot of filter surface is adequate. Use only potassium alum for coagulation and not the so-called ammonia alum. The ammonia alum introduces large amounts of ammonia into the pool water. This ammonia combines with the chlorine present forming chloramines, greatly increasing the chlorine demand of the water. Some common problems associated with sand filters are: A. Plugging. Routine inspections of the filter bed should be made to see that the sand is free from dirt and channels. Slowly wash the filter with the cover off and check to see if the water leaks through the sand surface evenly. Uneven up-flow of the water indicates that the under-drain nozzles are clogged or that there are obstructions in the sand bed. Removal of the filter sand would be necessary to replace the nozzles. Occasionally, treatment with a strong solution of sodium bisulfate is effective to prevent clogging. Two pounds of sodium bisulfate are added per square foot of filter area. Allow the sand to soak about 12 hours and then backwash. Acid treatment of this type may cause some corrosion damage. In areas with hard water, care must be taken to prevent the precipitating calcium and magnesium salts in the water from causing scale buildup on the sand and under-drains, resulting in clogging that cannot be removed by backwashing. Chemical cleaning will be required in these cases. The use of water softeners for treating the pool water would be highly beneficial in these areas. B. Mud Balls. Mud balls consist of large accumulations of dirt and sand held together by organic growths. These organic growths may consist of filtered algae, bacterial organisms, or surface debris removed by the filters. Mud balls usually occur because of insufficient wash rate and the lack of chlorine in the filter influent. Maintaining clean filters may prevent mud balls. Provide a sufficient backwash rate of at least 15 gallons per minute per square foot of surface area. Chlorine should be fed ahead of the filters so that the sand is covered with a strong chlorine residual at all times. This will prevent bacterial and algae growths from forming on the filter surface. C. Oil and Grease. Frequently, the sand particles become coated with oils and grease as well as with an accumulation of hair and dirt. Detergents are effective in removing oil and grease from sand filters. Add a solution (approximately 1 pound of sodium hexametaphosphate per 100 gallons of 19

23 water) to the filter in an amount sufficient to cover the sand. Soak the sand several hours, re-circulating through the make-up water tank when possible. Drain to waste and thoroughly backwash. The filter piping should have a re-circulation line to permit re-circulation of the water from the effluent back to the influent for chemical cleaning of the filter media. This line should be about one-half the size of the main return piping. Sand contaminated with oil and grease had been traditionally cleaned with a lye solution. This procedure should only be used if other materials are not effective. Lower the water level in the filter to within 2 inches of the top of the sand and apply the lye at a rate of 1 pound per square foot of the sand surface. Allow the upper portion of the sand to soak several hours and slowly empty the filter to waste. Follow with a longer than usual backwash. This treatment will prevent replacement of costly filter sand. Provide adequate wash water flow rates to prevent further accumulation of such conditions. Use extreme caution when handling lye as it can cause severe burns. Lye is particularly destructive to the tissue of the eye and may cause loss of sight. 5.4 HIGH RATE SAND FILTERS High rate sand filters may be operated at filter flow rates of up to 10 gallons per minute per square foot of surface area (as compared to 2 to 3 for conventional sand filters). Filtration is accomplished in-depth rather than on the surface, thereby, increasing the dirt holding capacity of the filter. Operation and cleaning of high rate sand filters should be compliant with the instructions supplied by the manufacturer. Usually the filter is back-washed when the differential pressure reaches 25 psi. The design of the under drain system causes strong agitation, rubbing together the sand grains to release suspended materials. Trade literature indicates that the collected solids are generally discharged during the first minute or less of backwash water source within about 2 minutes. Recommended backwash periods vary, but for some filters it is approximately 2 ½ minutes. High rate sand filters have had erratic success in North Dakota. Operation of the filter at a considerably reduced flow rate after back washing may prove beneficial. The reduced flow will allow the suspended materials to collect and settle on the sand, rather than being driven completely through the clean filter media. Once a coating of suspended material has been built up on the filter surface, the flow may be increased to the normal re-circulation rate. 5.5 DIATOMACEOUS EARTH FILTERS This type of filter has several advantages over the sand filter; greater removal of turbidity, smaller size and the elimination of chemical coagulants such as alum. They also require very little water for back washing. 20