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Swimming Pool Terms Glossary

Swimming pools themselves are simple, right? Well, sometimes they are! However, there are terms and words that come up from time to time which can stump even the most experienced pool service tech.

Listed below are many of the common words and phrases for equipment, chemicals, water testing and part replacement. How many times have you tried to explain a problem to your pool tech and just couldn't find the right words? Now with a little practice, you can be an expert! Or if he tells you "your impeller is stuck." you can see exactly what an impeller is and what it does!

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Acid A sour chemical substance that releases hydrogen ions with the ability to dissolve metals, neutralize alkaline materials and to combine with bases to form salts. Acid is used to lower (decrease) pH and total alkalinity of swimming pool and spa water. Examples are muriatic acid (hydrochloric) and dry acid (sodium bisulfate). All liquids with a pH lower than 7.0 are acidic or acid.
Acid Demand The amount of acid required to bring high pH and total alkalinity down to their proper levels. Determined by the Acid Demand Test.

Acid Demand Test A reagent test usually used in conjunction with a pH test to determine the amount of acid needed to lower high pH and total alkalinity levels.

Acid Rain Precipitation having an unusually low pH value (4.5 or lower) caused by absorption of air polluted by sulfur dioxide, carbon dioxide and nitrous oxide.

Acid Wash A procedure using an acid solution to clean the interior surface of a plaster, gunite, marcite or shotcrete pool with subsequent neutralization of the acid.

Activated Carbon A granular medium material (available in granular, powdered or block form) produced by heating carbonaceous substances (coal) or cellulose bases (wood, coconut shells) in the absence of air. The carbon has a very porous structure and may be used as an adsorbent for organic matter and dissolved gases in water.

Aeration The bringing about of intimate contact between air and water by bubbling air through the water or by drawing air in through a hydrotherapy jet or venturi.

Agglomeration The gathering of fine suspended matter in water into flocs or larger masses that then can settle and be filtered from the water.

Aggressive Water Water that is corrosive because it is low in pH, alkalinity or calcium hardness.

Aggregate The major component of plaster, composed of sand, marble dust, pebbles and other solid material.

Air Blower Mechanical device that forces air through holes in the floor, bubbler ring or hydrotherapy jets in a spa.

Air Relief Valve A brass or plastic manually operated valve located at the top of a filter tank for relieving the pressure inside the filter and for removing the air inside the filter (called bleeding the filter). Sometimes called a pressure relief valve.

Air switch A pneumatic control device used to operate pool and spa equipment safely. A button located near the water and convenient for use is pushed which sends air pressure through a small flexible tube or hose to a switch.

Algae Microscopic plant-like organisms that contain chlorophyll. Algae are nourished by carbon and use sunlight to carry out photosynthesis. They are introduced by rain or wind and grow in colonies producing nuisance masses. Algae are not disease-causing but they can harbor bacteria and they are slippery. There are 21,000 known species of algae. The most common pool types are black, blue-green, green and yellow or mustard. Pink or red colored algae-like organisms exist but are bacteria and not algae. Maintaining proper sanitizer levels, shocking and superchlorination will prevent their occurrence.

Algaecide – also Algicide – A natural or synthetic chemical designed to kill destroy or control algae.

Algaestat – also Algistat – Any chemical or substance that inhibits the growth of algae.

Alkali – also called Base – A class of compounds which will react with an acid to give a salt. A substance that creates a bitter taste and a slippery feel when dissolved in water. An alkali has a pH greater than 7.0 and is the opposite of an acid. Alkalis may include the soluble hydroxide, carbonate and bicarbonate salts of calcium, magnesium, potassium, and sodium. A reaction between an acid and a base is called a neutralization.

Alkalinity – also more commonly called total alkalinity – A measure of the pH-buffering capacity of water. Also defined as the water's resistance to change in pH. Composed of the hydroxides, carbonates and bicarbonates in the water expressed in ppm or mg/L. One of the basic water tests necessary to determine water balance. The ideal range is from 60 to 140 ppm.

Alum The most common chemical is aluminum sulfate. Any one of several aluminum compounds used in pools to form a gelatinous floc on sand filters or to coagulate and precipitate suspended particles in the water.

Ammonia Introduced into the water by swimmers as waste (perspiration or urine). Quickly forms foul-smelling, body-irritating chloramines – a disabled less effective form of chlorine. See chloramines or combined chlorine.

Amperage (amps) The term used to describe the strength of an electrical current. It represents the volume of current passing through a conductor in a given amount of time. Amps = watts ÷ volts.

Anode The electrode (positive) that attracts negatively charged anions. The positive pole of an electrodialysis system.

Anti-Foam A chemical added to the water to make the suds or foam go away. These products do not remove the source of the sudsing. Most often, the water must be drained and refilled to remove the soaps, oils and other causes of foaming. Shocking, superchlorination, clarifiers and enzymes may help remove the causes.

Anti-Scalant A chemical that inhibits or delays precipitation and subsequent scale formation.

Anti-Vortex Drain Cover A cover or grate attached to the main drain that prevents a vortex (whirlpool) from forming as the water passes through.

Ascorbic Acid A chemical compound used to remove iron stains from fiberglass and vinyl pools. It is Vitamin C and can also be used to dechlorinate or debrominate water.

Automatic Controller A device that automatically executes the decision making necessary to determine the proper adjust of a chemical parameter. Controllers are currently capable of automatically adjusting pH and sanitizer levels in water.

Automatic Pool Cleaner Pool maintenance system that will agitate or vacuum debris from the pool interior.

Available Chlorine Content A term used or an index used to compare the oxidizing power of chlorine-containing products to gas chlorine. It permits easy comparison of chlorine compounds. Gas chlorine provides 100 percent available chlorine, trichlor provides 90 percent available chlorine, Cal Hypo provides 75 percent available chlorine, Dichlor provides 56 or 62 percent available chlorine, Lithium Hypo provides 35 percent available chlorine, and sodium hypochlorite (liquid chlorine) is 10-12 percent by weight which means a gallon contains about 1 pound of pure chlorine.

Available Chlorine The amount of chlorine, both free and combined in the pool water that is available to sanitize or disinfect the water. Sometimes called residual chlorine.

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Knowing as much as you possibly can about your swimming pool makes life a whole lot easier! Swimming pool maintenance and vacuuming becomes a breeze, repairs are easier to diagnose, and when ordering parts you have all the information you need to make your purchase quick and simple.