Pool Care Terms Glossary, Labels, and Concepts

A Pool Care Glossary is an invaluable tool, given the vast array of terms, labels, and concepts that can be challenging to navigate. It provides definitions and explanations for various pool maintenance and water treatment terms and concepts, enabling individuals to make more informed decisions about their pool care and its impact on their health.

Pool care essentially involves the regular maintenance and treatment of the water and surfaces in a swimming pool. The glossary includes definitions for concepts like pH balance, chlorine levels, and filtration systems, among others. Pool owners can use this knowledge to better understand the impact of pool maintenance on their health and make beneficial changes to their overall well-being.

Understanding pool care and water treatment terminology is crucial for making informed decisions regarding one’s health and well-being.


1. What is Acid?

Acid is a chemical compound that lowers pH by contributing hydrogen ions to a water solution. It is the opposite of a base.

2. What is Acid Demand?

Acid Demand refers to the amount of acid needed to bring the water pH to a specific level.

3. What is Aggressive Water?

Aggressive Water is water with corrosive properties due to low pH, calcium hardness, and/or total alkalinity.

4. What is Algae?

Algae is a general class of microscopic plant life that includes many species. It enters water by rain, wind, dust, storms, or tap water. Some float freely in the water; others grow on surfaces.

5. What is Algaestat?

Algaestat is a chemical that inhibits the growth of algae.

6. What is Algicide (a.k.a. Algaecide)?

Algicide, also known as Algaecide, is any chemical that kills algae.

7. What is Alkali?

Alkali, also known as Base, is a chemical that neutralizes acids, usually by furnishing hydroxyl ions (OH). It is the opposite of an acid.

8. What is Alkalinity?

Alkalinity, also known as Total Alkalinity, is a measure of the capacity of water to neutralize acids.

9. What is Alum?

Alum, also known as Aluminum Sulfate, is a white solid chemical that brings together fine particles in water to form larger particles that can be filtered (Flocculant).

10. What is Ammonia (NH)?

Ammonia is a chemical compound of hydrogen and nitrogen that combines with free chlorine in pools to form inorganic chloramines (Combined Chlorine).

11. What is Ammonium Hydroxide (NH OH)?

Ammonium Hydroxide is an ammonia and water mixture used for detecting chlorine gas leaks.

12. What is Amperometric Probe?

An Amperometric Probe is an electrode that measures changes in current within the probe due to changes in concentrations of specific chemicals in water.

13. What is Anion?

An Anion is an ion that has a negative charge.

14. What is Atom?

An Atom is the smallest particle into which matter can be broken by ordinary means. Atoms combine with other atoms to form molecules or chemical compounds.

15. What are Automatic Feeders?

Automatic Feeders are chemical feeders that have valves controlled by electronic equipment to deliver needed chemicals. The electronic device (controller) receives signals from electrodes (probes) that monitor the water’s properties.

16. What is Available Chlorine Content?

Available Chlorine Content is the relative strength of a chlorine-releasing chemical compared to elemental chlorine gas (Cl,), which is arbitrarily assigned an available chlorine content of 100%.

17. What is Backwash?

Backwash is the process of cleaning a swimming pool filter by reversing the flow of water through the filter.

18. What is Backwash Rate?

Backwash Rate is the rate of flow required for efficient filter cleaning. Typically measured as the volume of water (gallons or litres) per minute per filter surface area.

19. What are Bacteria?

Bacteria are single-celled microorganisms that lack chlorophyll and reproduce by fission. They play many important positive roles in human life, but some are also pathogenic (disease causing).

20. What is Bactericide?

Bactericide is any chemical that kills bacteria.

21. What is Balanced Water?

Balanced Water refers to the correct ratio of hardness, alkalinity, temperature, dissolved solids, and pH that prevents pool water from being either corrosive or scale forming.

22. What is a Barrier?

A Barrier is a device or system of devices that control access to a pool, spa, or other recreational water. Barriers may include fencing or walls, pool or spa covers, surrounding buildings, etc.

23. What is Base Demand?

Base Demand is the amount of alkaline material needed to achieve a specific pH level.

24. What is Bather Load?

Bather Load is the number of bathers in the water at a given moment or during a specific period of time. Maximum allowable bather loads are often regulated in public pools and spas.

25. What is Bicarbonate Alkalinity?

Bicarbonate Alkalinity is that portion of the total alkalinity composed of bicarbonate (HCO,) and carbonate (CO,).

26. What is Calcium Carbonate (CaCO,) (a.k.a. Scale)?

Calcium Carbonate, also known as Scale, is a water-insoluble white solid that is the major component of scale.

27. What is Bleach?

Bleach, also known as Sodium Hypochlorite, is a chemical compound often used as a disinfectant or a bleaching agent.

28. What is Calcium Chloride (CaCI,)?

Calcium Chloride is a soluble white salt used to raise the calcium hardness level.

29. What is Bluestone?

Bluestone, also known as Copper Sulfate, is a chemical compound used for various purposes including as an algaecide in swimming pools.

30. What is Calcium Hardness?

Calcium Hardness is the calcium portion of the total hardness. The level of calcium determines whether water is overly soft (too little) or hard (too much). Excessively high hardness levels may cause cloudy water and scale. Excessively low levels may harm the pool.

31. What is Body Coat?

Body Coat is a layer of filter medium like diatomaceous earth or another material on a filter element.

32. What is Body Feed (a.k.a. Slurry Feed)?

Body Feed, also known as Slurry Feed, is diatomaceous earth fed constantly or intermittently during a filter run to produce a layer of material over the filter elements.

33. What is Borax (Na, B,O, 5H,O)?

Borax is a naturally occurring mineral in the form of a white powder that is used to soften water, add buffering capacity, or inhibit the growth of algae.

34. What is Breakpoint Chlorination?

Breakpoint Chlorination is the elimination of inorganic chloramines by adding enough Free Chlorine to destroy the inorganic chloramines that contribute to combined chlorine. Ten times the Combined Chlorine minus the existing Free Chlorine is used.

35. What is Bridging?

Bridging refers to an excessive buildup of a body coat on diatomaceous earth filter elements to the point where the body coats of two adjacent elements touch.

36. What is Broadcasting?

Broadcasting is a method of distributing chemicals broadly over a water surface.

37. What is Bromide (Br)?

Bromide is a salt that contains the bromide anion.

38. What is Bromine (a.k.a. 1-bromo-3-chloro-5,5-dimethylhydantoin or BCDMH; 1,3-dibromo-5,5-dimethylhydantoin or DBDMH; bromide/oxidizer)?

Bromine is a generic term used to describe any chemical that releases hypobromous acid when dissolved in water. Elemental bromine (Br,), a brown liquid, is no longer used to treat recreational water.

39. What is Bromine Feeder?

A Bromine Feeder is a chemical feeder designed specifically to dissolve chemicals that release hypobromous acid into water.

40. What is 1-Bromo-3-chloro-5,5-dimethylhydantoin (a.k.a. BCDMH)?

1-Bromo-3-chloro-5,5-dimethylhydantoin, also known as BCDMH, is a type of bromine used in water treatment.

41. What is a Buffer?

A Buffer is a mixture of chemicals added to water that causes the solution to resist pH change. The amount of buffer in the water is measured by the total alkalinity.

42. What is Calcification?

Calcification is the formation of calcium carbonate scale on pool walls or the surface of circulation system components due to the precipitation of calcium carbonate.

43. What is Calcium Hypochlorite (Ca(OCI),) (a.k.a. Cal Hypo)?

Calcium Hypochlorite, also known as Cal Hypo, is a white solid disinfectant and oxidizer that releases chlorine (Hypochlorous Acid) when dissolved in water. It is available as granules, briquettes, and tablets. It contains from 65-78% available chlorine content in the industrial grade, or less in formulated products.

44. What is Calibration?

Calibration is the process of checking or adjusting (by comparison with a standard) the accuracy of a measuring instrument.

45. What is Carbon Dioxide (CO,)?

Carbon Dioxide is a gas that is used to lower pH in water.

46. What is a Cartridge Filter?

A Cartridge Filter is a filter that uses a replaceable and disposable porous element as the filter medium.

47. What is a Cation?

A Cation is an ion with a positive charge.

48. What is Caustic Soda?

Caustic Soda, also known as Sodium Hydroxide, is a strong base used in many industries, primarily as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents.

49. What is Cavitation?

Cavitation is the formation of partial vacuums when the pump volume exceeds the water supply.

50. What is Centrifugal Force?

Centrifugal Force is the outward force exhibited by anything in circular motion. It is the principle by which water is propelled through a circulation system by a pump impeller.

51. What is a Certified Pool & Spa Operator (CPO) Certification?

A Certified Pool & Spa Operator (CPO) Certification is a certification for an individual who has satisfied the classwork requirements and demonstrated knowledge of course material by passing the examination administered by PHTA certified instructors.

52. What is Channeling?

Channeling is the creation of paths through a sand media bed caused by water hardness, organic load, or by exceeding the filter media rate. This allows water to bypass the filter medium and not remove solids from the water.

53. What is a Check Valve?

A Check Valve is a device that limits flow in a pipe to a single direction.

54. What is a Chelating Agent?

A Chelating Agent, also known as a Sequestering Agent or Complexing Agent, is an organic chemical that forms more than one bond to metal ions in solution, forming complexes that have different properties than the metal ion.

55. What is Combined Chlorine?

Combined Chlorine, also known as Combined Available Chlorine or Chloramine, is the chemical species that forms when chlorine chemically bonds to nitrogen-containing compounds like urine, perspiration, dead algae, etc. Combined chlorine can cause eye and skin irritation and has a strong chlorine-like odor.

56. What is a Chemical Feeder?

A Chemical Feeder is a device that dispenses chemicals into water at a predictable rate. It may be controlled automatically or manually.

57. What are Chloramines?

Chloramines are the same as Combined Chlorine. They form when chlorine chemically bonds to nitrogen-containing compounds.

58. What is a Contaminant?

A Contaminant, also known as an Impurity, is a substance that makes another substance impure.

59. What are Chlorinated isocyanurates?

Chlorinated isocyanurates are a family of stabilized chlorine disinfectants used commonly to destroy germs and algae in pools and spas.

60. What is Coping?

Coping refers to the deck edge around a pool or spa water surface.

61. What is Copper Sulfate?

Copper Sulfate, also known as Blue Stone or Cupric Sulfate, is a blue water-soluble solid used on its own or in formulated products to kill algae.

62. What is a Chlorinator?

A Chlorinator is any chemical feeder used to dispense any form of chlorine.

63. What is Chlorine?

Chlorine is a heavy, green, highly poisonous gas compressed in liquid form and stored in heavy steel tanks. It is used in swimming pools as a disinfectant and algicide. Extreme caution must be used in handling.

64. What is Chlorine Demand?

Chlorine Demand is the amount of free chlorine that is consumed by the contaminants that are readily oxidized by chlorine.

65. What is a Chlorine Generator?

A Chlorine Generator is a device that uses electrolysis to convert sodium chloride (salt) or sodium bromide into free chlorine or total bromine.

66. What is Chlorine Residual?

Chlorine Residual is the same as Residual.

67. What is Circulation?

Circulation refers to the flow or movement of water through a given area or volume including the pool or spa vessel and through the pump, filter, heaters, feeders, and any other system components.

68. What is a Clarifier?

A Clarifier is a chemical that causes small particles to combine into larger particles that can be removed by a filter.

69. What is Clarity?

Clarity refers to the degree of transparency of pool water. It is characterized by the ease with which an object can be seen through a given depth of water or by use of a turbidity meter.

70. What is Coagulation?

Coagulation, also known as Flocculation, is the process of separating or precipitating solids suspended in a liquid as a result of the particle’s growth.

71. What are Coliform Bacteria?

Coliform Bacteria is a family of bacteria common in soils, plants, and animals. The coliform family is made up of several groups, one of which is the fecal coliform group found in the intestinal tracts of warm-blooded animals including humans. They may cause gastroenteritis in humans.

72. What is Cyanuric Acid?

Cyanuric Acid, also known as Stabilizer, Conditioner, or 2,4,6-trihydroxy-s-triazine, is a white, granular solid chemical that reduces the loss of chlorine due to the ultraviolet rays from sunlight.

73. What is a Deck?

A Deck is the area immediately surrounding or next to a pool or spa, giving bathers room for sitting, standing, or accessing the water.

74. What is a Defoamer?

A Defoamer is a product designed to remove foam from pool and spa water typically containing silicone emulsions.

75. What is a Degreaser?

A Degreaser is a product designed to remove grease from filters.

76. What does Dermal refer to?

Dermal refers to the skin.

77. What is the Design Rate of Flow?

The Design Rate of Flow is the average rate of flow used for design calculations in a system.

78. What is Emissivity?

Emissivity refers to the relative ability of a surface to emit radiant energy.

79. What is a Diaphragm Pump?

A Diaphragm Pump is a positive displacement metering pump in which a diaphragm isolates the operating parts of the pump from the liquid. It is used in conjunction with one-way suction and discharge check valves to provide a constant and adjustable feed rate regardless of varying injection pressures, flow rates, and liquid levels.

80. What is Diatomaceous Earth (D.E.)?

Diatomaceous Earth (D.E.) is a white powder composed of fossilized skeletons containing microscopic pores from one-celled organisms called diatoms. It is used as a replaceable filter medium for D.E. swimming pool filters.

81. What is a Diatomaceous Earth Filter?

A Diatomaceous Earth Filter, also known as a D.E. Filter, is a filter designed to use diatomaceous earth, cellulose fiber, volcanic ash, or other such specially formulated filter medium on a filter element. It may be either a pressure or a vacuum type.

82. What is Dichlor?

Dichlor refers to Sodium dichloro-s-triazinetrione.

83. What is Diethyl-p-phenylenediamine (DPD)?

Diethyl-p-phenylenediamine (DPD) is a reagent used in test kits or strips to measure and indicate either total or free available chlorine. The presence of chlorine turns the reagent pink.

84. What is Dilution?

Dilution is the process of reducing the concentration of a substance or chemical in solution, usually simply by mixing with more water.

85. What is a Disinfectant?

A Disinfectant, also known as a Sanitizer, is an agent that destroys microorganisms that might carry disease.

86. What is Disinfection?

Disinfection, also known as Sanitization, is the process of destroying microorganisms that might cause disease.

87. What is Dry Acid?

Dry Acid refers to Sodium Bisulfate.

88. What is a Dry Feeder?

A Dry Feeder is a device consisting of a small, electrically operated, revolving auger in the bottom of a hopper that feeds solids into water.

89. What is Effluent?

Effluent is the outflow of water from a filter, pump, or other system component.

90. What is an Enzyme?

Enzymes are proteins that are produced by living cells that catalyze (cause) chemical reactions to take place without the enzyme itself being altered or destroyed.

91. What is an Equalizer Line?

An Equalizer Line is a flow 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.

92. What is Erosion?

Erosion is the process of wearing away a solid substance by running water.

93. What is an Erosion Feeder?

An Erosion Feeder is a chemical feed device in which powder, tablets, sticks, or briquettes are placed in a container and through which a water stream is passed, eroding and dissolving the chemical.

94. What are Feet of Head?

Feet of Head is a basic measurement of pressure or resistance in a hydraulic system that is equivalent 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, fittings, or vessel.

95. What is Ferric Iron?

Ferric Iron, also known as Fe3+ or Fe(III), is a brown water-insoluble iron ion precipitate.

96. What is Ferrous Iron?

Ferrous Iron, also known as Fe2+ or Fe(II), is a green water-soluble iron ion. When exposed to an oxidizer, it will convert to ferric ion, which can precipitate from water.

97. What is a Filter?

A Filter is a mechanical device for separating suspended particles from water. It refers to the complete mechanism including all component parts.

98. What is a Filter Cartridge?

A Filter Cartridge is a disposable element, usually of fibrous material, used as a filter septum in some pool filters. It may filter dirt from the water at the cartridge surface or allow penetration of smaller suspended particles within the matrix of fibers.

99. What is a Filter Cycle (a.k.a. Filter Run Time)?

A Filter Cycle, also known as Filter Run Time, refers to the amount of time of filter operation between backwash and cleaning procedures.

100. What is an Electrode (a.k.a. Probe)?

An Electrode, also known as a Probe, is a device placed in a liquid or mounted in a liquid stream that measures specific water properties based on the conductance of electricity within the device. It is usually linked to an automatic controller.

101. What is a Filter Element?

A Filter Element refers to a filter cartridge, or that part of a D.E. filter on which the filter aid is deposited.

102. What is Electrolysis?

Electrolysis is a method by which chemical reactions are carried out by passing an electrical current through a substance. Examples include chlorine generation or ionizers.

103. What is Filter Media Rate?

Filter Media Rate is the rate of flow of water through a filter during a set period of time expressed in U.S. gallons per minute per square foot of effective filter area.

104. What is Filter Medium?

Filter Medium is the portion of the filter that performs the separation of solids from liquid including sand, cartridge, or diatomaceous earth.

105. What is Hardness (water)?

Hardness in water refers to the quantity of dissolved minerals, chiefly calcium and magnesium compounds, in the water. It may be measured as Total Hardness (TH), which includes both calcium and magnesium hardness, or as Calcium Hardness (CH), which isolates only the calcium portion of the Total Hardness. Improper water balance may lead to these minerals being deposited as scale in pipes, pools, and heaters.

106. What is Filter Sand?

Filter Sand is a type of filter media composed of hard, sharp silica, quartz, or similar particles with proper grading for size and uniformity.

107. What is Filter Septum?

Filter Septum is that part of a filter on which diatomaceous earth or similar filter media is deposited. It usually consists of cloth, wire screen, or other fine mesh material.

108. What is Floc?

Floc is a gelatinous substance resulting from the use of a flocculant.

109. What is a Flocculant?

A Flocculant is a chemical that brings together fine particles in water to form larger particles. It is a compound usually used with sand-type filters to form a thin layer of gelatinous substance on the top of the sand, aiding in trapping fine suspended particles that might have passed through the sand.

110. What is a Flow Meter?

A Flow Meter is a device that measures pressure differential across a calibrated orifice and indicates the rate of flow at that point, usually given in gallons per minute or litres per minute.

111. What is a Foot Spray?

A Foot Spray is a device for spraying bather’s feet with water or a disinfectant. It is usually a shower head at knee height used to rinse sand, soil, and grass from feet before entry into the pool.

112. What is Free Chlorine (a.k.a. FC or Free Available Chlorine)?

Free Chlorine, also known as FC or Free Available Chlorine, is the portion of total chlorine that is not combined chlorine and is available as disinfectant (HOCI, and OCr). It is the portion of total chlorine that reacts with DPD.

113. What is Friction Head?

Friction Head refers to the head lost by flow in a stream due to friction between water and the piping and by friction between water molecules.

114. What are Gallons per Minute (gpm)?

Gallons per Minute (gpm) is a measurement of water flow rate.

115. What is Galvanic Corrosion?

Galvanic Corrosion is the corrosion of metals that occurs when two or more dissimilar metals are immersed in an electrolyte, including pool water.

116. What is Gastroenteritis?

Gastroenteritis is an inflammation of the stomach and intestines.

117. What is a Gutter?

A Gutter is an overflow trough at the edge of a pool.

118. What is a Hair & Lint Strainer?

A Hair & Lint Strainer is also known as a Pump Strainer.

119. What is Hypochlorous Acid (HOCI)?

Hypochlorous Acid (HOCI) is an unstable acid with excellent bactericidal and algicidal properties. It is the active agent by which chlorine serves as a disinfectant. It is formed by dissolving chlorine gas, hypochlorites, chlorinated isocyanurates, or any other chlorinating agent in water. It is in dynamic equilibrium with hypochlorite ion (OCl-), dependent on the pH of the water.

120. What is Melamine?

Melamine is the reagent used to test for cyanuric acid and cyanurate concentrations in pool or spa water.

121. What is a Micron?

A Micron is a unit of measure representing one millionth of a meter, or one thousandth of a millimeter.

122. What is a Microorganism?

A Microorganism is a microscopic plant or animal.

123. What are Milligrams Per Litre (mg/L)?

Milligrams Per Litre (mg/L) is another term for Parts Per Million.

124. What is a Molecule?

A Molecule is a group of atoms bound together in a specific arrangement.

125. What is Monopersulfate?

Monopersulfate refers to Potassium Monopersulfate and Non-Chlorine Oxidizers.

126. What is a Multiple Filter Control Valve (Multi-port Valve)?

A Multiple Filter Control Valve, or Multi-port Valve, is a special switching valve with a separate position for each of various filter operations such as normal filter operation, backwash, rinse, recirculate, waste, and closed.

127. What is an Impeller?

An Impeller is the rotating part of a centrifugal pump.

128. What is an Impurity?

An Impurity, also known as a Contaminant, is any unwanted substance that is not originally part of a system or product.

129. What is Influent?

Influent refers to water flowing into a pool, pump, filter, chemical feeder, or other space.

130. What is Iodine?

Iodine is a blue-black crystalline chemical element of the same chemical family as chlorine and bromine. It is no longer used to treat pool or spa water.

131. What is an Ion?

An Ion is an isolated atom or molecule that has gained or lost an electron and has acquired a negative or positive charge, respectively.

132. What is an Ionizer?

An Ionizer is a device that releases heavy metal ions, such as copper or silver, into water. It is used in conjunction with a residual disinfectant such as chlorine or bromine. This device combines in one unit the functions of several direct-flow valves including filtration, backwash, drain, and circulation.

133. What is Muriatic Acid?

Muriatic Acid is another term for Hydrochloric Acid.

134. What is Isocyanurate?

Isocyanurate is another term for Chlorinated Isocyanurates.

135. What are Non-Chlorine Oxidizers?

Non-Chlorine Oxidizers are products other than chlorine that oxidize body wastes, organic matter, or reduce combined chlorine or chloramines. These products may not kill bacteria or algae. Many non-chlorine oxidizers are sold for pool and spa use, including potassium monopersulfate, hydrogen peroxide (H2O2), and sodium percarbonate (NaHCO3).

136. What is a Lifeguard?

A Lifeguard is an individual with the proper training and skills designed to keep bathers of aquatic facilities safe in and around the water.

137. What is a Lifeline?

A Lifeline is a rope line across a pool to designate a change in slope in the pool bottom or the beginning of deep water. It is usually supported by regularly spaced floats.

138. What is a Lint Strainer?

A Lint Strainer, also known as a Pump Strainer, is a container installed in the pump suction line with a removable basket, designed to protect the pump from debris in the water flow.

139. What is Lithium Hypochlorite (LiOCl)?

Lithium Hypochlorite is a white granular solid disinfectant that contains 35% available chlorine content.

140. What is a Logarithm?

A Logarithm is a mathematical term. In pool usage, it represents 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.

141. What is Makeup Water?

Makeup Water is potable water used to fill or refill a pool or spa.

142. What is a Manometer?

A Manometer is an instrument that measures pressure differential across an orifice by means of a column of liquid, usually mercury.

143. What is Marcite?

Marcite is a regional term used to describe pool plaster, specifically plaster containing a marble (calcium carbonate) aggregate.

144. What is Organic Waste?

Organic Waste refers to the portion of several contaminants in water (perspiration, body oils, urine, saliva, suntan oil, cosmetics, and/or contaminants) that contain carbon atoms. Other sources of organics in the water may include spilled food, animal wastes, soil, pollen, remnants of plants, etc.

145. What are Organisms?

Organisms refer to plant or animal life. In the context of pool water, it usually refers to algae (plant), bacteria, viruses, or protozoa.

146. What is an Orifice?

An Orifice is an opening, usually calibrated in size, through which liquid or gas flows.

147. What is an Orifice Plate?

An Orifice Plate is a disc with a sharp edged, circular opening 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.

148. What is Orthotolidine (a.k.a. OTO)?

Orthotolidine (OTO) is a test reagent that turns yellow in the presence of total chlorine or total bromine. At higher concentrations, OTO darkens to gold and brown. OTO is a suspected carcinogen and banned by some health departments.

149. What is an Overflow Gutter (a.k.a. Overflow Trough or Scum Gutter)?

An Overflow Gutter is a trough around the top perimeter of a pool. It is used to remove the water on the surface either to waste or to a filter.

150. What is Oxalic Acid?

Oxalic Acid is a weak organic acid, usually contained within products designed to remove metal stains from pool walls and floors or to clean rust from filter septa.

151. What is Oxidation?

Oxidation is the process of changing the chemical structure of water contaminants by increasing the number of oxygen atoms or reducing the number of electrons in the contaminant.

152. What is Oxidation Reduction Potential (a.k.a. ORP)?

Oxidation Reduction Potential (ORP) is a method of measuring the potential, which often relates to the concentration of an oxidizer in the water. ORP probes send signals to electrical controllers that can open valves on chemical feeders to dissolve and release disinfectants into the water.

153. What is an Oxidizer?

An Oxidizer is a substance capable of increasing the number of oxygen atoms or reducing the number of electrons in another chemical.

154. What is Polyhexamethylene Biguanide (a.k.a PHMB)?

Polyhexamethylene Biguanide (PHMB) is a disinfectant used largely in residential pools or spas as part of a program that includes an oxidizer (hydrogen peroxide) and an algaecide that is compatible with biguanide.

155. What is Polymeric Clarification?

Polymeric Clarification is the process of using a large organic chemical to flocculate contaminants and clear cloudy or colored water.

156. What is Potable?

Potable refers to water that is safe and suitable for drinking.

157. What is Potassium Alum (a.k.a. Potassium Aluminum Sulfate)?

Potassium Alum, also known as Potassium Aluminum Sulfate, is a flocculant in sand filter operation.

158. What is Potassium Monopersulfate (KHSO5) (a.k.a. Potassium Peroxymonopersulfate)?

Potassium Monopersulfate, also known as Potassium Peroxymonopersulfate, is a non-chlorine oxidizer used to reduce contaminants or to activate bromide ions to produce hypobromous acid.

159. What are Pounds per Square Inch (a.k.a. psi)?

Pounds per Square Inch (psi) is a U.S. unit of measure for pressure or head.

160. What is a Precipitate?

A Precipitate is a solid substance separating from a liquid as a result of a chemical or physical change to the environment. For example, the formation of scale or a scum line.

161. What is Ozone (O3)?

Ozone is a gaseous oxidizer and supplemental disinfectant that is generated on-site, and then dissolved into water to oxidize contaminants and disinfect the water containing the ozone. Ozone is generated either by UV light or by a corona-discharge generator.

162. What are Parts per Million (a.k.a. ppm)?

Parts per Million (ppm) is the amount of item being measured in one million units. In dilute water solutions, the weight volume relationship of milligrams per litre (mg/L) may be substituted.

163. What is a Pathogen?

A Pathogen is a microorganism that causes disease in humans.

164. What is Perlite?

Perlite is created from siliceous volcanic rock or glass. Like D.E., the product contains some crystalline silica, which has been linked to the lung disease silicosis, so care should be taken when using this product.

165. What is pH?

pH is the negative logarithm of the hydrogen-ion concentration of a water solution. It is 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.

166. What is Phenol Red?

Phenol Red is an organic dye that is yellow at a pH of 6.8 and then turns progressively deeper red and purple in color as the pH increases to 8.4. It is the most commonly used test reagent for pH in pools.

167. What is a Pump Curve?

A Pump Curve is a graph of performance characteristics of a given pump under varying power, flow, and resistance factors. It is used in checking and choosing a pump.

168. What is a Pump Strainer (a.k.a. Lint Strainer, Pump Pot, or Hair and Lint Trap)?

A Pump Strainer, also known as a Lint Strainer, Pump Pot, or Hair and Lint Trap, is a container installed in the pump suction line with a removable basket, designed to protect the pump from debris in the water flow.

169. What is a Probe?

A Probe, also known as an Electrode, is a device used to measure specific properties in a solution, such as pH or oxidation reduction potential.

170. What are Protozoa?

Protozoa are single-celled parasites that cause gastroenteritis (stomach diseases) and release oocysts which are resistant to disinfectants, in the feces of the victim. These oocysts can then infect other bathers. The most common pool-related protozoa are Giardia and Cryptosporidium.

171. What is a Pump Curve?

A Pump Curve is a graph of performance characteristics of a given pump under varying power, flow, and resistance factors. It is used in checking and choosing a pump.

172. What is a Sequestering Agent?

A Sequestering Agent is a chemical that forms a complex with a metal ion to prevent the precipitation of the metal ion. The sequestering agent is often used to form a complex that will precipitate from solution to remove the metal from water.

173. What is a Pump Strainer (a.k.a. Lint Strainer, Pump Pot, or Hair and Lint Trap)?

A Pump Strainer, also known as a Lint Strainer, Pump Pot, or Hair and Lint Trap, is a container installed in the pump suction line with a removable basket, designed to protect the pump from debris in the water flow.

174. What is a Pressure Differential?

A Pressure Differential is the difference in pressure between two points in a hydraulic system, such as the difference in pressure between the influent and the effluent points of a filter, a pump, a venturi tube, or an orifice plate.

175. What is a Pressure Filter?

A Pressure Filter is a filter through which dirty water is pushed by a pump mounted on the influent side of the filter.

176. What is a Precoat?

A Precoat is the layer of diatomaceous earth deposited on the filter septa at the start of a filter run with D.E. filters.

177. What is a Precoat Feeder?

A Precoat Feeder is 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.

178. What is a Service Factor?

A Service Factor refers to the degree to which an electric motor can be operated above its rated horsepower without the risk of overload failure.

179. What are Quaternary Ammonium Compounds (a.k.a. Quat)?

Quaternary Ammonium Compounds, also known as Quat, are a family of chemicals used in various mixtures and concentrations to kill and prevent algae growth.

180. What is a Skimmer?

A Skimmer is a device other than an overflow trough used for the continuous removal of surface water and floating debris from a pool. Water drawn through the skimmer goes to the filter.

181. What is a Rate of Flow Indicator?

A Rate of Flow Indicator is also known as a Flow Meter.

182. What is a Recirculating System?

A Recirculating System is the entire system of pipes, pumps, and filters that allows water to be taken from the pool, filtered, treated, and then returned to the pool.

183. What is a Skimmer Weir?

A Skimmer Weir is also known as a Weir.

184. What is a Slurry Feed?

A Slurry Feed is a suspension of solid in water that is easily pumpable.

185. What is a Reducing Agent?

A Reducing Agent is a substance capable of neutralizing oxidizers.

186. What is Sodium Bicarbonate (NaHCO3) (a.k.a. Baking Soda)?

Sodium Bicarbonate, also known as Baking Soda, is a powder used to raise the total alkalinity content of a pool with a small change in pH.

187. What is Sodium Bisulfate (NaHSO4) (a.k.a. Dry Acid)?

Sodium Bisulfate, also known as Dry Acid, is a white powder that lowers pH and alkalinity.

188. What is Sodium-Carbonate (Na2CO3) (a.k.a. Soda Ash)?

Sodium-Carbonate, also known as Soda Ash, is a white, water-soluble solid used to raise the pH and alkalinity of pool water.

189. What is Sodium dichloro-s-triazinetrione (C3N3O3Cl2Na) (a.k.a. Dichlor or Dichloroisocyanuric acid)?

Sodium dichloro-s-triazinetrione, also known as Dichlor or Dichloroisocyanuric acid, is a white solid disinfectant and oxidizer that releases chlorine (hypochlorous acid) and cyanuric acid (stabilizer) when dissolved in water. It is available in tablet or granular products. It contains about 56%-63% available chlorine content in the industrial grade, or less in formulated products.

190. What is Sodium Hydroxide (NaOH) (a.k.a. Caustic Soda or Lye)?

Sodium Hydroxide, also known as Caustic Soda or Lye, is a corrosive solid with a very high pH (14) that is usually sold in a liquid form to raise pH and alkalinity.

191. What is Sodium Hypochlorite (NaOCl) (a.k.a. Bleach or Liquid Chlorine)?

Sodium Hypochlorite, also known as Bleach or Liquid Chlorine, is a liquid disinfectant and oxidizer that releases chlorine (hypochlorous acid) when added to water. It contains between 10% to 15% available chlorine for swimming pool products and about 5% for household products.

192. What is Sodium Percarbonate (NaHCO3)?

Sodium Percarbonate is a white solid oxidizer that generates hydrogen peroxide when dissolved in water.

193. What is Sodium Sesquicarbonate (Na2CO3 • NaHCO3 • 2H2O)?

Sodium Sesquicarbonate is a solid white chemical used to raise the pH and alkalinity of pool water. This chemical has properties similar to a 50:50 blend of sodium carbonate and sodium bicarbonate.

194. What is Sodium Sulfite?

Sodium Sulfite is a chemical used to neutralize oxidizers in water including disinfectants like chlorine and bromine.

195. What is Sodium Thiosulfate (Na2S2O3)?

Sodium Thiosulfate is a chemical used to remove chlorine from water. It is used to remove 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.

196. What is a Spa (a.k.a. hot tub, hydrotherapy pool, whirlpool, or swim spa)?

A Spa, also known as a hot tub, hydrotherapy pool, whirlpool, or swim spa, is a small recreational water vessel, usually designed for soaking as opposed to swimming. Spas are usually equipped with features and devices such as benches for sitting, venturi jets, air bubble bars, heated water, etc. Because of the smaller water volume, use, and water temperature, spas must be treated differently than pools.

197. What is a Stabilizer?

A Stabilizer is also known as Cyanuric Acid.

198. What does it mean to Sterilize?

To Sterilize means to kill all microorganisms.

199. What is a Suction Head?

A Suction Head is the distance in feet a pump on the inlet side must raise the water from the pool or spa to the level of the pump.

200. What is a Suction Outlet?

A Suction Outlet is a location within a pool or spa through which water is drawn by a pump through the circulation system.

201. What is Suction Piping?

Suction Piping is the piping or tube that feeds into the inlet side of a pump.

202. What is Sulfuric Acid (a.k.a. Pool Acid)?

Sulfuric Acid, also known as Pool Acid, is a mineral acid made up of sulfur, oxygen, and hydrogen. The structural formula of sulfuric acid is H2SO4. This mixture is a colorless, odorless liquid that is soluble in water, and is used to lower the pH of pool water.

203. What is Superchlorination?

Superchlorination is the practice of adding large quantities of a chlorinating chemical to kill algae and microorganisms, eliminate slime, destroy odors, or improve the ability to maintain a disinfectant residual.

204. What is a Supplemental Disinfectant?

A Supplemental Disinfectant is a chemical that kills pathogens, but does not maintain an adequate residual to maintain a sanitary state in pool or spa water.

205. What is Surface Area?

Surface Area can refer to: a. The amount of water exposed to the air in a pool or spa, usually measured in square feet or square meters. b. The amount of plaster (or other interior pool coating material) exposed to the water, usually measured in square feet or square meters. c. The area of filter medium available to filter water, usually measured in square feet or square meters.

206. What is Sodium Sulfite?

Sodium Sulfite is a chemical used to neutralize oxidizers in water including disinfectants like chlorine and bromine.

207. What is a Surge?

A Surge refers to the displacement of water in a system, such as by bathers in a pool.

208. What is a Surge Tank?

A Surge Tank is a holding tank, pit, or vessel designed to offset surge displacement in a pool.

209. What is a Titrant?

A Titrant is a standard solution of known concentration used for titration.

210. What is Titration?

Titration is a method of analyzing the composition of a water solution by adding known amounts of a standardized solution until a given reaction and color change occurs.

211. What is Total Alkalinity?

Total Alkalinity is a measure of the ability of the water to maintain a desirable pH when acid is added to the water. This value is usually expressed as the equivalent amount of calcium carbonate (CaCO3) in either mg/L or ppm.

212. What is Total Chlorine (a.k.a. TC or Total Available Chlorine)?

Total Chlorine, also known as TC or Total Available Chlorine, is the total of all free available chlorine and combined chlorine in the water.

213. What are Total Dissolved Solids (TDS)?

Total Dissolved Solids (TDS) is the amount of residue that would remain if all the water evaporated or was removed. It is expressed as the mass of solid per the total initial volume of water (ppm or mg/L). It is typically measured by electrical conductance.

214. What is Total Dynamic Head?

Total Dynamic Head is a measure of a system’s resistance to flow.

215. What is Total Hardness (TH)?

Total Hardness (TH) is the total of all calcium hardness and magnesium hardness in water.

216. What is Trichloro-s-triazinetrione (C3N3O3Cl3) (a.k.a. Trichlor or Trichloroisocyanuric acid)?

Trichloro-s-triazinetrione, also known as Trichlor or Trichloroisocyanuric acid, is a disinfectant that releases chlorine (hypochlorous acid) and cyanuric acid (stabilizer) when dissolved in water. It is available as an active ingredient in tablet or granular products.

217. What is a Trihalomethane (CHX3)?

A Trihalomethane (CHX3) is a potentially carcinogenic chemical produced by the reaction between either chlorine or bromine with organic contaminants in water. It consists of one carbon atom (methane) with three halogen (X) atoms (chlorine or bromine) bound to the carbon.

218. What is Turbidity?

Turbidity is a measure of the cloudiness or haziness of an otherwise clear liquid due to the presence of small liquid or solid particles in the liquid. Turbidity is measured in Nephelometer Turbidity Units (NTUs).

219. What is a Virus?

A Virus is a microscopic infectious agent that replicates itself within living cells; many are pathogenic (disease-causing). They are carried and passed from infected people or animals. The most common pool-related viruses are Norwalk, Hepatitis A, and Adenovirus.

220. What are Voids?

Voids refer to spaces in or between particles or fibers of a filtering medium. These spaces determine the permeability and the dirt-holding capacity of the filter.

221. What is Volume?

Volume is a measure of the size of a three-dimensional space. Typically, it refers to the amount of water that occupies that space measured in gallons, cubic feet, or litres. One U.S. gallon is equivalent to 3.79 litres. One cubic foot is equivalent to 28.3 litres.

222. What is a Weir?

A Weir is a flap within a skimmer that adjusts automatically to small changes in water level and assures a continuous water flow to the skimmer.

223. What is Winterizing?

Winterizing is a method of closing a pool for the off-season. This may include preparing for cold or freezing conditions with both chemical and mechanical strategies for the pool and the facility.

224. What is Zeolite?

Zeolite is a family of minerals containing hydrated aluminum silicates formed in cavities in lava flows and in plutonic rocks. It is used as a filter medium that may be used in place of sand in sand filters.

225. What is a Turnover Rate?

A Turnover Rate is the time it takes (in hours) to circulate an amount of water equivalent to the volume of the pool or spa.

226. What is Ultraviolet Light (UV)?

Ultraviolet Light (UV) is electromagnetic radiation with a shorter wavelength (higher frequency) than visible light that is part of the spectrum of light emitted by the sun or can be generated artificially. It is subdivided into three wavelengths: UV-A (315-400 nanometers), UV-B (290-315 nanometers), and UV-C (220-290 nanometers). It is used to generate ozone and as a supplemental disinfectant to inactivate microorganisms. Exposure to UV light can lead to sunburn and ultimately skin cancer.

227. What is an Underwater Light?

An Underwater Light is a fixture designed to illuminate a pool from beneath the water’s surface. It 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.

228. What is a Vacuum Cleaner?

A Vacuum Cleaner is one of several types of suction devices designed to collect dirt from the bottom of the pool. Some vacuums discharge dirt from the bottom of the pool, some discharge dirt and water into the filter, some discharge to waste, and some collect debris in a porous container, allowing water to return to the pool. Some vacuums are self-propelled; others must be manually pushed or pulled across the pool.

229. What is a Vacuum Filter?

A Vacuum Filter is a filter through which dirty water is pulled by a pump mounted on the effluent side of the filter.

230. What is a Valve?

A Valve is a device used to control, restrict, or redirect the flow of water through the circulation system. It includes backwash, multi-port, gate, ball, bleeder, and other types of valves.

231. What is Velocity?

Velocity is the distance water travels in a unit of time expressed in feet per second or meters per second.

232. What is a Venturi Tube?

A Venturi Tube is a tube mounted in a water line that causes restriction of flow. The restriction causes a pressure differential that can be used to draw a liquid or a gas into the water line.