A chemical compound that releases hydrogen ions in water solution.
Microscopic forms of plant life that enter the pool by rain, wind and dust storms. There are numerous varieties – some are free floating; others grow on walls and surfaces and come in different colors. Some are more resistant to chemical treatment than others.
Chemicals that prevent and control algae. Some prevent algae growth; others are designed to kill specific types of visible algae growth.
A chemical that inhibits the growth of algae.
The property of a compound that allows it to neutralize an acid.
The amount of bicarbonate, carbonate and hydroxide compounds present in water solution. A measure of the pH buffering capacity of water.
Any one of several aluminum compounds used in pools to form a gelatinous floe on sand filters or to coagulate and precipitate suspended particles in water. Most commonly refers to aluminum sulfate. aluminum sulfate See above.
An ammonia and water mixture used for detecting chlorine leaks.
A chemical compound of hydrogen and nitrogen that combines with free chlorine in pools to form chloramines, or combined chlorine. ammonia nitrogen Brought into pools by swimmers: perspiration, urine or waste. Reacts with chlorine to form chloramines. Causes eye irritation.
Ammonium aluminum sulfate. No longer used as a flocculent or coagulant in pools due to chloramine formation. anthracite Hard coal.
Trade name for anthracite specifically ground into particles of the proper size to be used in a swimming pool filter. atom The smallest particle into which matter can be broken by ordinary means. Combines with other atoms to form molecules of chemical compounds. automatic feeders Electronic equipment that senses water variables (primarily chlorine and pH) and controls feed systems to maintain desired levels. available chlorine Chlorine, both free and combined, that is active to some degree against bacteria in pool water. average head The resistance to flow of water in a pool recirculation system obtained by averaging the maximum and minimum resistance encountered in the course of a filter run.
The process of cleaning a swimming pool filter by reversing the flow of water through it.
The rate of flow, in gallons per minute per square foot of filter surface area, required for efficient filter cleaning.
Microorganisms present in all water supplies. Some are necessary to life; others cause disease. bactericide Any chemical that kills bacteria.
The correct ratio of mineral content and pH level that prevents pool water from being corrosive or scale forming.
A chemical that neutralizes acids. Usually by furnishing hydroxyl ions.
Common name for copper sulfate, an effective algicide that is declining in popularity as a swimming pool algicide because of its toxicity and incompatibility with some pool chemicals.
Diatomaceous earth that builds up on a filter element during the course of a filter run to help maintain filter porosity.
Diatomaceous earth fed constantly or intermittently during a filter run to produce a body coat.
A tube, closed at one end, that measures pressure against air trapped in the tube. It is used as the basic element in many pressure gauges and flow meters in swimming pool instrumentation.
The point in a rising chlorine residual at which the concentration of available chlorine becomes great enough to oxidize all organic matter and ammonia compounds in a pool com pletely. Chlorine added thereafter will be in an uncombined, or free, state. Breakpoint is charac terized by a sudden drop in total residual available chlorine. The magnitude of the drop depends upon the amount of combined chlorine present and other factors.
Buildup of a body coat on diatomaceous earth filter elements to the point where the body coats of two adjacent elements touch.
A chemical compound containing bro mine, sodium or potassium bromide in solution; will produce free bromine if an oxidizer is introduced.
A chemical dye sensitive to changes in pH. Used to test pH over a range of 6.0 to 7.6. Turns from yellow to blue as pH increases.
Formation of calcium carbonate on the walls of pools or pipes, or in a filter, due to the precipitation of calcium carbonate. Also refers to incrustation caused by magnesium hydroxide.
The calcium portion of the total hardness. About 65 75% of total hardness. Concentrations of calcium determine whether water is “soft” (too little) or “hard” (too much). Higher hardness levels can cause cloudy water and scale. Lower levels can harm the pool and its equipment.
A compound of chlorine and calcium used in white granular or tablet form as a bactericide in pools. In water solution, it provides 65% available chlorine. Must be handled with care.
A pool water filter that uses paper or fabric like cartridges as its filtering medium.
The outward force exhibited by anything in circular motion. The principle by which water is propelled through a circulation system by a pump impeller that imparts circular motion to the water in a pump.
Any of several types of devices that dispense chemicals into pool water at a predictable rate. Types include diaphragm, pis ton, erosion, peristaltic, dry and vacuum.
Compounds formed when chlorine combines with nitrogen from urine, perspiration, etc. Chloramines cause eye and skin irritation, as well as unpleasant odors.
Any chemical feeder used to dipense any form of chlorine, often used conversationally to refer specifically to gas chlorinators.
A heavy, green, highly poisonous gas compressed in liquid form and stored in heavy steel tanks. Used in swimming pools as a bactericide and algicide. Extreme caution must be used in handling.
The amount of chlorine neces sary to oxidize all organic matter present in pool water, chloramines, bacteria and algae.
The amount of available chlo rine remaining in pool water after the chlorine demand has been satisfied.
The degree of transparency of pool water. Characterized by the ease with which an object can be seen through a given depth of water.
A chemical, usually alum, used in pools for the purpose of gathering and precipitating suspended matter.
Bacteria found in the intes tines of warm blooded animals. Their presence in pool water indicates the possibility of the presence of disease causing bacteria.
Chlorine that has combined with a nitrogen compound, usually ammonia, forming compounds known as chloramines. Al though combined chlorine does have some bacteri cidal powers, it is far less effective than free chlorine.
Impure. Can refer to presence of harmful bacteria in water or to the presence of any unwanted substance in any other substance.
An effective algicide, declining in popularity for pool use because of its toxicity and incompatibility with some other compounds found in pools.
Caused by unbalanced and aggressive water. Metal parts are eaten away, usually due to acidity or very soft water conditions.
An unprotected connection be tween a domestic water supply and a pool or other non potable water where a contamination of the domestic system could occur. Protective devices must be used to eliminate possible contamination.
The chemical 2,4,6, trihydroxy triazine, also known as stabilizer or conditioner. It stops sunlight from dissipating chlorine strength.
The average rate of flow used for design calculations in a system. Usually refers to gallons per minute per square foot of filter surface area.
A chemical feeder of the posi tive displacement type in which an electrically operated flexing diaphragm in conjunction with one way suction and discharge check valves makes possible constant, repeatable and adjust able feed rate regardless of varying injection pressures, flow rates and liquid levels.
White powder composed of fossilized skeletons of one celled organisms called diatoms. Porous, containing microscopic spaces. Used as a filter medium for swimming pools.
A filter designed to use diatomaceous earth or volcanic ash as a filter medium. May be either pressure or vacuum type. Commonly called a D.E. filter.
(NHCI2) A poor disinfectant that gives off disagreeable odor and irritates the eyes.
Percent of HOCI at varying temperatures and pH values.
A chemical that will destroy infection causing organisms.
A process of filtering water to waste after backwashing to insure that all pipes in the system are free of debris before beginning a filter run.
The preferred reagent used in test kits to measure and indicate free available chlorine. The presence of chlorine turns the indicator pink.
The granular chemical (sodium bi sulfate) that slowly lowers pH and total alkalin ity. Safer to handle than liquid (muriatic) acid.
A chemical or D.E. feed device consist ing of a small, electrically operated, slowly revolving auger in the bottom of a hopper.
The outflow of water from a filter, a pump or a pool.
A sensor placed in a sample for meas urement and control of water variables through automation.
Thermodynamics, the relative ability of a surface to emit radiant energy compared to an ideal, black body at the same temperature and with the same area.
Flow of electrical current through a liquid solution by means of electrically charged ions. Usually produces corrosion of metals in the liquid.
A chemical feed device in which powder, tablet or sticks are placed in a closed container through which a regulated stream of pool water is allowed to flow, gradually eroding the chemical. Feed rate varies with flow velocity.
A line from below the pool surface to the body of a skimmer, designed to prevent air being drawn into the filter when the water level drops below the skimmer inlet. Operates automatically.
The piping, with all valves and fittings, that is used to connect the filter systemtogether as a unit. This includes all valves and piping necessary for the filter plant to perform the functions of filtering or backwashing, either by the plant as a whole or any unit operating singly.
A basic measurement of pressure or resistance in a hydraulic system that is equiva lent to the height of a column of water that would cause the same resistance. The DYNAMIC HEAD is the sum of all the resistance in a complete system when in operation. The principle factors of”head~ are vertical distances and resistance due to friction of the flow against the walls of the pipe or vessel. FRICTION HEAD is the head due to friction only.
Compounds of iron that are insoluble in water and will precipitate.
Compounds of iron that are soluble in water and will impart a clear green color. filter A mechanical device for straining suspended
Usually refers to powder like substance such as diatomaceous earth or volcanic ash used to coat a septum type filter. Can also be used to refer to alum as an aid to sand filtration.
A disposable element, usually of fibrous material, used as a filter septum in some.
The time of filter opera tion between backwash procedures.
A filter cartridge, or that part of a D.E. filter on which the filter aid is deposited. filter media Any fine grain material, carefully graded as to size, that entraps suspended parti cles as water passes through.
The rate of flow of water through a filter during the filtering cycle expressed ingallons per minute per square foot of effective filter area.
Graded, rounded rock or gravel used to support filter media. filter sand A type of filter media composed of hard, sharp silica, quartz or similar particles with proper grading for size and uniformity.
That part of a filter on which diatomaceous earth or similar filter media is deposited. Usually consists of cloth, wire screen or other fine mesh material.
A compound usually used with sand type filters to form a thin layer of gelatinous substance on the top of the sand. Aids in trapping fine suspended particles that might pass through the sand.
A gelatinous substance re sulting from the use of a floccueant.
(See rate of flow indicator).
A shallow water area between bath house showers and pool deck through which pool patrons must walk. Originally designed to contain a disinfectant solution for control of athlete’s foot. Because it was proved to be ineffective, the foot bath has either been eliminated or modified to contain a continuous flow of clean water.
A device for spraying bathers’ feet with water or a disinfectant. Usually a shower head at knee height to rinse sand and grass from feet before entry into the pool. free chlorine Also called available, usable chlo rine. It is the most active form of chlorine that is free to kill bacteria and algae.
Creation of electrical current by electro chemical action.
Corrosion of metals that occurs when two or more dissimilar metals are immersed in an electrolyte. gutter Overflow trough at edge of pool.
Refers to the quantity of dis solved minerals, chiefly calcium and magnesium compounds, that may be deposited as scale in pipes, pools and heaters.
(See feet of head.
Also called MURIATIC ACID when diluted. A very strong acid used in pools for pH control and for certain specific cleaning needs. A byproduct of the addition of chlorine gas to water. Use extreme care in handling.
The lightest chemical element. A com ponent of water and a frequent product of many chemical reactions. In its ionic form it is used as a measure of acidity and pH.
The positively charged nucleus of a hydrogen atom. Its presence in water solution is used as a measure of acidity of the solution.
A negatively charged particle com posed of one hydrogen atom and one oxygen atom.
A chemical feeder through which liquid solutions of chlorine bearing chemicals are fed into the pool water at a controllable rate.
Refers to any compound containing a metal and the (OC1 ) radical. Most commonly refers to calcium, sodium or lithium hypochlorite in pool usage.
An unstable acid with excellent bactericidal and algicidal proper ties. The active agent by which chlorine serves as a disinfectant. Formed by dissolving chlorine gas, any hypochlorite or other chlorinating agent in water. impeller The rotating vanes of a centrifugal pump.
Water flowing into a pool, a pump, a filter, a chemical feeder or other space.
A chemical compound containing iodine. Potassium or sodium iodide, when used with a suitable oxidizing agent such as chlorine, will release iodine in pool water.
A blue black crystalline chemical element of the same chemical family as chlorine and bromine. An excellent bactericide in pool water solution. Not effective as an algicide.
A rope line across a pool to designate a change in slope in the pool bottom or the beginning of deep water. Usually supported by regularly spaced floats.
A device mounted in the pump influent line to screen out lint and other debris that might cause damage to the pump.
Chemicals used to reduce pH and total alkalinity in pool water. Most common types are muriatic and sulfuric. They are extremely corro sive and dangerous chemicals to handle.
A mathematical term. The number that represents the power to which a given number must be raised to obtain another number. In pool usage, the power to which 10 must be raised to equal the reciprocal of the hydrogen ion concentration of the pool water. It is represented by the term pH.
Fresh water used to fill or refill the pool.
An instrument that measures pres sure differential across an orifice by means of a column of liquid, usually mercury. In pools, usually calibrated to show rate of flow of water in gallons per minute.
A unit of measure representing one mil lionth of a meter, or one thousandth of a millimeter. microorganism A microscopic plant or animal.
The smallest particle to which a chemi cal compound can be reduced without destroying its chemical composition.
A special switching valve with a separate position for each of various filter operations. Combines in one unit the functions of several direct flow valves.
A dilute solution of hydrochloric acid.
An element introduced into the pool via perspiration, hair spray, cosmetics, etc. Reduces the effectiveness of chlorine; stimulates algae growth. Forms eye irritating chloramines (See chloramines).
National Spa and Pool Institute. A trade organization of people and institutions in the swimming pool and spa industry.
National Swimming Pool Foundation. A research, education and safety organization representing both the pool industry and the general public.
An opening, usually carefully calibrated in size, through which water flows.
A disc with a sharp edged, circular orifice in the center. When placed in a water flow line, it creates a pressure differential to operate a rate of flow indicator, chemical feeder or other hydraulic mechanism.
The perspiration, urine, saliva and suntan oil that swimmers introduce into a pool. When these wastes accumulate, they must be chemically oxidized because most won’t filter out.
Plant or animal life. Usually refers to algae or bacteria like growth in pool water.
An organic test reagent (also called OTO) that turns yellow green in the presence of chlorine, bromine or iodine.
Trough around the top pe rimeter of a pool. Used to skim the surface of the water to waste or to filters. Also called scum gutter.
A mild organic acid, usually pur chased as a solid white granular substance. Used specifically to dissolve rust stains on pool walls and floors or to clean rust from filter septa. Poisonous; use with care.
A microorganism that causes disease in man.
The negative logarithm of the hydrogen ion concentration of a water solution. A measure of the degree of acidity or alkalinity of a solution. A pH below 7.0 is considered acid. A pH above 7.0 is considered alkaline. Above 7.8, the water is too alkaline and could cause cloudiness and scale formation. Below 7.2, the water is too acidic and could cause corrosion and plaster etching. Im proper pH also affects chlorine’s germ killing power and causes swimmer discomfort.
An organic dye that is yellow at a pH of 6.8 and turns progressively deeper red in color as the pH increases to 8.4. The most commonly used test reagent for pH in pools.
A flocculating agent designed to clear cloudy or colored water. Rapidly collects, settles and allows for easy removal of dead algae, insoluble minerals and suspended iron, copper or manganese.
May filter dirt from the water at the cartridge surface or allow penetration of smaller suspended particles into internal interstices.
Water that is safe and suitable for drinking.
Potassium aluminum sulfate. Sometimes used as a floccueant in sand filter operation.
A non chlorine oxidizer used to shock treat pool and spa water and to activate bromide ions to produce hypobromous acid.
Calculated in weight units. In dilute water solution, the weight volume relationship of milligrams per liter may be substituted. Equals i/~o,ooo of 1%.
Pounds per square inch. Commonly, a unit of pressure or head.
An insoluble compound, such as cal cium carbonate, that may appear in a solution as the result of chemical action. For example, addition of chlorine to a pool containing dissolved iron will cause a reddish precipitate of insoluble iron compounds.
A chemical feeder designed to inject diatomaceous earth into a filter in sufficient quantity to coat the filter septa at the start of a filter run.
The difference in pressure between two points in a hydraulic system. As the difference in pressure between the influent and the effluent points of a filter, a pump, a venturi tube or an orifice plate.
A graph of performance charac teristics of a given pump under varying power, flow and resistance factors. Used in checking and choosing a pump.
A device containing a removable strainer basket designed to protect a pump from debris in the water flow when installed in the pump suction line. Also called lint strainer or hair and lint catcher.
A family of compounds (also known as “quats”) used in various mixtures and concentrations to combat algae growth in pools. May cause foam on the surface of the water due to their ability to decrease the surface tension.
A device that measures pressure differential across a calibrated orifice and indicates the rate of flow at that point. Usually in 8pm.
The entire system of pipes and pumps and filters that allows water to be taken from the pool, filtered, treated and returned to the pool.
(See chlorine residual).
The name given to a pool water circulation system in which water is taken from the surface of the pool and returned through inlets at the bottom of the pool.
A ring shaped floating buoy capable of supporting a drowning person. Usually attached to 50 to 60 feet of light line and kept at poolside for rescue use.
A pool filter using sand, or sand and gravel as a filter medium.
A mathematical calculation, based on the interrelation of temperature, cal cium hardness, total alkalinity and pH, that predicts if the pool water is corrosive, scale forming or neutral.
Calcium carbonate deposits that can befound deposited in the filter, heater or on pool wall. Generally caused by high mineral content combined with high pH.
A chemical that when added to pool water keeps dissolved metals and minerals in clear solution.
The degree to which an electric motor can be operated above its rated horsepower without danger of overload failure.
A device other than an overflow trough for continuous removal of surface water and floating debris from a pool. Usually returns water so removed to the filter system.
Part of a skimmer that adjusts automatically to small changes in water level to assure a continuous flow of water to the skimmer.
Body feed for a D.E. filter introduced as a liquid slurry.
A chemical feeder designed to handle a gritty slurry without clogging.
Sodium carbonate (Na2CO3) used to raise pH and increase total alkalinity in pool water. Also to react with alum to produce floe on sand filters and to neutralize hydrochloric acid resulting from use of chlorine gas for chlorination.
A chemical (NaHCO3) used to raise total alkalinity content of a pool with little change in pH.
A dry white powder (NaHSO4) that produces an acid solution when dissolved in water. Used in pools to lower pH. Safer to handle than hydrochloric acid.
(NaOCl) A liquid that provides 12% to 15% available chlorine. One of the most commonly used products for chlorination of pools. Produces hypochlorous acid when added to pool water. Use care when handling.
Chemical solution used to remove all chlorine from a test sample to avoid false pH test readings or false bacteria test results. It is also used in larger quantities to dechlorinate swimming pools.
A particularly rough, coarse form of scale. Formed when the calcium hardness of water is 100 ppm or less.
(See cyanuric acid).
To kill all microorganisms by heat or chemical action.
The prac tice of adding 8 10 times the normal chlorine dose to destroy algae or reach breakpoint for the reduction of chloramines.
The number of persons in the pool area at any given moment, or during a stated period of time.
The total amount of carbonates, bicarbonates and hydroxides in the pool. Total alkalinity affects and controls pH. If total alkalin ity is too high, pH will be hard to adjust. If it’s too low, pH will be unstable, difficult to maintain within the desired range. The total alkalinity level should be 80 to 150 ppm, depending on sanitizer.
Degree to which suspended particles in pool water obscure visibility.
The number of times a quantity of water equal to the total capacity of the pool passes through the filters in a stated time. Usually in turnovers per 24 hours.
The distribution at the bottom of a sand filter to collect the filtered water during a filter run and to distribute the backwash water during backwash.
A lighting fixture designed to illuminate a pool from beneath the water surface. May be “wet niche” located in the pool water, or “dry niche” located in the pool sidewall behind a waterproof window and serviced from outside the pool.
One of several types of suction devices designed to collect dirt from the bottom of the pool. Some discharge dirt and water into the filters, some discharge to waste, and some collect debris in a porous container, allowing water to return to the pool. Some are self propelled; others must be pushed or pulled across the pool.
A filter, usually of the D.E. type, through which water is pulled by a pump mounted on the effluent side of the filter.
The rate of movement of water in feet per second.
A tube mounted in a water line so as to cause restriction of flow. The constriction causes a change in velocity of water through the tube, resulting in a pressure differential that is proportional to the flow rate. The pressure differential can be used to measure flow or operate hydraulic chemical feeders.
Spaces in or between particles or fibers of a filtering medium. These spaces determine the permeability and the dirt holding capacity of the filter.
A fine white porous powder similar to diatomaceous earth but lighter in weight. Used as a filter medium or filter aid in D.E. type filters.