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Glossary of Swimming Pool Terms

Whats New:

Astral Swimming Pool Parts Diagrams has been updated with five new products, Including Astral Multiport Valves. Please call 954-442-1066

Updated: June 14, 2016

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Recent Events:

Whitefly Invasion

demo The Whitefly arrived in Florida in 2009. Today it is found from the Florida Keys to the Palm Beaches. Areas infested leave a "honeydew-like" like film on pools that rapidly depletes chlorine. A favorite host to the white fly is the coconut palm, often found near pools. If you are experiencing rapid chlorine depletion that cannot be explained by any other means, contact you pool professional.

Updated: August 2014

Swimming Pool Chemical Glossary of Pool Terms

Swimming pool equipment general information including: MSDS, water chemistry, parts diagrams and directory of swimming pool manufacturers.

A liquid or dry chemical, used to lower the pH of Swimming pool or spa water. See Muriatic Acid(Hydrochloric Acid) or sodium bisulfate.
  Acid Demand The amount of acid needed to bring the pH into the desired range of 7.2-7.6
  Algae Small plants that propogate by air borne process. Upon entering a swimming pool they can turn water green, yellow or cause black or dark green stains. Best dfense is to maintain a free chlorine residual at all times.
A natural or synthetic substance used for killing, destroying or controlling algae.
  Algaestat A chemical used to prevent algae growth.
  Algae Spores Dormant or resting algae in the atomosphere introduced into a swimming pool by wind, rain, showers, dust storms, etc.
Alkalinity Increaser
A chemical used to stabilize the pH. Sodium Bicarbonate
Aluminum Sulfate (Al2SO4), which is used to cause suspended solids in water to be coagulated and subsequently filtered or vacuumed out.
  Backwash Reversing the flow of water thru a filter with the purpose removing contaiminats.
  Bacteria Miscrsopic Organsism typically brought into the pool by living beings.
  Balanced Water Swimming Pool Wtaer that has a pH between 7.2-7.6 and contains proper levels of Alkalinity and Calcium and ideally has a Langellier Saturation index of +/- 0.3
  Base A chemical when added to the water increases the pH
  Base Demand A liquid or dry chemical, used to increase the pH of Swimming pool or spa water. See Sodium Carbonate or Sodium Bicarbonate.
An alternate sanitizer to chlorine, the prinicipal santizer used in spas
Calcium Increaser
A chemical used to increase the water hardness (calcium Hypochlorite)
  Calcium Hypochlorite Bleach, Typically 5-10% chlorine content
  Cartridge Filter A filter using a replaceable element, Eliminates Backwashing, conserves water.
  Chloroamines Chlorine combined with ammonia. Strong Irritants and odor of chlorine.
  Chlorine The principal sanitizer used in pools to kill bacteria and algae, comes in gaseous, liwuid, powder and tablet forms.
  Chlorine Demand The amount of chlorine needed to zero. The amount of chlorine required to overcome the debris in the swimming pool, which may include algae, leaves, pollen, grass, etc.
  Cyanuric Acid The active ingredient in chlorine stabilizer or stabilizer, Prevents UV rays from breaking down the pool chlorine.
  Corrosion A chemical process which causes metal detioration. Caused by low pH or unbalanced water.
  Corrosion Resistance A material that maintains its original appearance and is not affected by conditions typically within a swimming pool.
  DE Diatomaceous Earth, Animal Skeletons ftom the ocean used as a filtration medium
  DPD A chemical reagent used to test chlorine, Both Free and Total Chlorine
A chemical having ability to kill undesirable or pathogenic organism, having a measurable residual at a level adequate to achieve the desired kill.
  Dry Acid A powder chemical, Sodium Bisulfate, used to lower the pH or Alkalinity,
  Effective Filtration Area The total filtration area, which controls the flow rate of water thru the filter.
  Feeder A mechanical devices used to introduce chemicals into a pool.
  Filter Aid Typically Diatomaceous Earth,or similiar material such as Perlite, used to coat the grids or elements of a DE Filter
  Flocculating Agent A chemical, substance or compound that promotes the combination, agglomeration or coagulation of suspended particles in water.
  Free Chlorine The active chlorine in the pool after the chlorine demand is meet
  GPM Gallons per minute. Important that the pump and filter are matched to the proper GPM.
  Hardness The amount of Calcium, Magnesium, Iron, Carbonates, sulfates, chlorides, silicates dissolved in water. When the Langellier Saturation Idex is greater than +0.3 scaling may occur
  Hydrochloric Acid Muriatic Acid(HCl). A very strong corrosive acid. Used in swimming pools to lower the pH of the water.
  Hypobromous Acid The most powerful disinfecting form of Bromine
  Hypochlorus Acid The active form of Chlorine (HOCl)
  Hypochlorite A family of chemical compounds (salts), found in various forms(liquid, powder, tablets) used a a chlorinating agent. Forms Available: Sodium Hypochlorite (liquid), Lithium Hypochlorite (powder) and Calcium Hypochlorite (powder or tablets). Non-Stabilzed chlorine
  Iodine A chemical element that is biocidal, used to disinfect pool and spa water. The spa disinfectant is in the form of liquid iodine.
  Isocyanurates A family of pool sanitizer products that are self stabilizing. Also called stabilized chlorine
  Langelier Saturation Index A formula developed by Dr. W.F. Langelier to determine the scale forming or scaling propeirs of water
  Lithium Hypochlorite LiOCl. A white solid inorganic chlorine. pH approximately 9. Available chlorine 35%.
  Muriatic Acid Used to Lower pH and or Total Alkalinity in pools or spas (Hydrochloric Acid)
  OTO Orthotolidine. An indicator reagent used to measure chlorine, Cannot readily distingquish free chlroine with combined chlorine, Not preferred method of testing.
  Ozone A gaseous molecule composed of three (3) atoms of oxygen that is generated on site and used for oxidation of water and contamination.
  pH How basic or acidic water is. Less than 7.00 is acidic, requires a base to increase the pH greater than 7.0 is basic, requires an acid to lower the pH.
  Phenol Red A dye used to measure the pH of water.
  Potable Water Any water, that is approved for drinking. Contains no bacteria or other harmful chemicals
  Quats Quaternary Ammonium Compounds: Organic compounds used as algaecide or germicides.
  Sequestering Agent Sometimes referred to as Chelating agents. These compounds are capable of combining with metals (copper, Iron, Etc.) to prevent staining of the pool surface
  Sand Filter Filter using Silica Sand as a medium. Requires Backawahing.
  Service Factor Motor Related Term used to express the overload built into a motor.
  Shock Treatment Introduction of 5-10 times the normal amount of chlorine into a pool, the purpose of which is to remove chloramines or kill algae.
  Soda Ash Sodium Carbonate: A white powder (chemical) to increase the pH of the water
  Sodium Carbonate See Soda Ash (Na2C03)
  Sodium Bicarbonate A white powder used to increase Alkalinity (Baking Soda, NaHC03))
  Sodium Bisulfate A white powder used to lower pH (NaHS04)
  Sodium Dichloro-isocyanurate

Dichlor (sodium dichlori-s-triazinetriaone), a granular product, containing approximately 62% chlorine. Fast Dissolving, non-clouding, oxidizer. Can be used for maintenance and shocking (pH 6.0)

  Sodium Hypochlorite A clear liquid (bleach), typically 5-15% available chlorine.
  Source Water Water used to fill a pool or spa. Can be Potable or from wells.
  Stabilizer See Cyanuric Acid.
  TDS Total Dissovled solids, Everything ever added to the pool, can lead to problems with chlorination of the pool. A factor used in the Langelier Saturation index.
  Total Alkalinity A measure of the pools ability to resist changes in pH. High levels of cyanuric acid can contribute to the alkalnity, but may not help with stabilizing the pH
  Weir Part of the skimmer, that helps skim debris from the surface of the pool and prevents it from returning to the pool.

Links to Other Water Chemistry Topics

Calcium Deposits

Chlorine Products

Glossary of Chemical Terms

Potassium Monopersulfate

Saturation Index

Spa Disinfectants

Water Testing