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Swimming Pool Glossary


CALCIUM CARBONATE: Crystalline compounds formed on swimming pool surfaces when the calcium hardness, pH or total alkalinity levels are too high. Once formed, the crystals adhere to the plumbing and pool surfaces. These crystals are also known as scale.

CALCIUM CHLORIDE: A soluble white salt used to raise the calcium hardness or total hardness level of pool water.

CALCIUM HARDNESS: The calcium content of the water. If the calcium hardness level is too low, the water may be corrosive. If the calcium hardness level is too high, the water may have a tendency to form scale.

CALCIUM HYPOCHLORITE: A compound of chlorine and calcium used as a disinfectant, sanitiser, bactericide, algaecide and oxidizer in swimming pool water. It is available as a white granular powder which usually contains 65% - 70% available chlorine and has a pH of 11.8 . It is also used as a disinfectant in drinking water.

CARBON DIOXIDE: A gas, which when present in the water, provides necessary nutrients for the algae to photosynthesise and reproduce in the presence of sunlight. Also used to lower pH in large pools.

CARTRIDGE: A disposable porous element made of paper or polyester which is used as the filter medium in cartridge filters.

CARTRIDGE FILTER: A water filter that uses a replaceable porous element made of paper or polyester.

CHECK VALVE: A mechanical device in a pipe that permits the flow of water in one direction only. Also called a one-way valve or a non-return valve.

CHELATOR: A chelating agent is a water soluble molecule that can bond tightly with metal ions, keeping them from coming out of suspension and depositing their stains and scale onto pool surfaces and equipment. Similar to sequestering agents.

CHELATED COPPER: Copper algaecides that contain a special ingredient to prevent the copper from staining the pool surfaces or producing coloured water.

CHEMICAL FEEDER: A device that dispenses chemicals into the pool water at a predetermined rate. Some provide chlorine or bromine while others add pH-adjusting chemicals.

CHLORAMINES: Undesirable smelly compounds formed when insufficient levels of free available chlorine react with ammonia and other nitrogen containing compounds (swimmer waste, sweat, urine, ...). Chloramines are a threat to human health and are very poor sanitisers. Chloramines can be destroyed by shock treatment or superchlorination.

CHLORINATOR: A mechanical or electrical device for adding chlorine to a pool at a controlled rate. Most often a floater filled with tablets of chlorine or an in-line feeder.

CHLORINE: A member of the halogen family of sanitisers. Its use in swimming pools is in the form of a gas, as a liquid, in granular or tablet forms. When added to water it acts as an oxidiser, sanitiser, disinfectant and biocidal agent.

CHLORINE, combined: The measure of chlorine which has attached itself to other molecules or organisms, typically ammonia or nitrogen compounds. Most of these compounds are present as unwanted chloramines.

CHLORINE, free available: Free available chlorine is active chlorine and is not combined with any other molecule. A portion of the free available chlorine is present as hypochlorous acid, which reacts to destroy organic material in the pool water.

CHLORINE, total: The sum of combined and free available chlorine levels. With a DPD test kit, DPD1 determines free available chlorine and DPD3 shows total chlorine. The difference, if any, is the level of combined chlorine.

CHLORINE DEMAND: The amount of chlorine necessary to oxidise all organic matter (bacteria, algae, chloramines, ammonia and nitrogen compounds, . . .) in the pool water.

CHLORINE ENHANCER: A chemical compound used in conjunction with chlorine, that makes the chlorine perform better as an algaecide.

CHLORINE GENERATOR: An electrical device that generates chlorine from a salt solution. The salt solution may be in a separate tank or may be in the pool itself.

CHLORINE LOCK: If the level of cyanuric acid (stabliser) in the water is much over 80ppm, the chlorine becomes trapped and is unable to oxidise effectively. Despite being able to measure normal chlorine levels, the Redox potential is very low, indicating a lack of oxidiser. The only way to fix this is to drain some of the water and refill the pool. Care should be taken when using stabilised chlorine products (dichlor or trichlor) to avoid the level of cyanuric acid increasing too much.

CHLORINE NEUTRALISER: A chemical used to deactivate or destroy chlorine. It is used in better test kits to prevent the bleaching effect of the chlorine and consequently to increase the accuracy of the tests.

CHLORINE RESIDUAL: Also called Free Available Chlorine. The amount of chlorine left in the pool water after the chlorine demand has been satisfied.

CLARIFIER: Also called a coagulant or flocculant. A chemical compound used to coagulate, clump or precipitate suspended microparticles so they can be removed by vacuuming or filtration. There are two main types; inorganic salts of aluminum (alum), or organic polyelectrolytes.

CLARITY: The degree or measure of the transparency of water.

CLINOPTILOLITE: The zeolite that is used as an alternative to quartz as the filter medium in sand filters.

COAGULANT: An organic polyelectrolyte that helps the filter by clumping minute particles together so they can be trapped by the filter.

COMBINED CHLORINE: See Chlorine, combined.

COMPENSATION TANK: The tank into which the water from the gutters or skimmer gutters flows. The tank serves to ensure that the pool has enough water to overflow regardless of the number of swimmers and independent of evaporation and splash-out losses.

CONDITIONER: Chemically known as cyanuric acid and also called stabiliser. It protects chlorine in the water against the effects of the sun's UV rays.

CONTAMINANTS: The general name for any microparticle or organism which reduces water clarity, quality or presents health hazards. Filtering, oxidising and sanitising are necessary to destroy the contaminants.

COPPER: An effective algaestat and algaecide and is one of nature's natural elements. It may also be used in the equipment and plumbing in swimming pools. High levels of copper may stain hair, fingernails or pool surfaces and can also result in green, brown or blue water.

COPPER ALGAECIDE: A chemical compound that contains the element copper. Most copper algaecides contain ingredients that prevent the copper from staining but do not affect copper's ability to kill algae. These are known as chelated copper algaecides.

COPPER SULFATE: Copper sulfate was one of the original copper algaecides. It is similar to aluminium sulfate in that it provides a flocculant function in water. It can be used in ponds but may harm some aquatic creatures in high concentrations. The amount of copper required to be effective would stain swimming pools.

CORROSION: The effects of an acidic pool environment; one in which the pH and/or alkalinity are very low. Corrosion in the form of etching, pitting or erosion of pool equipment and surfaces is the result. May also be caused by misuse of acid or by soft water.

COVER, hard-top: A cover used on pools that rests on the edge of the pool deck and does not come into contact with the water.

COVER, solar: A floating cover that increases the water temperature by absorption and transmission of solar radiation and reduces evaporation and pollution from the environment.

COVER, winter: A cover that is secured around the edges of a pool when the pool is closed for the season.

CYANURIC ACID: Also called conditioner and stabiliser. A granular chemical added to the pool water which provides a shield to chlorine for protection from the sun's UV radiation. It is also found in dichlor/ trichlor products.

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D.E. FILTER: See Diatomaceous Earth Filter

DEFOAMER: Also called anti-foam. A chemical added to the water to destroy the foam. These products do not remove the source of the foaming. Shocking and superchlorination may help prevent foaming. Controlled use of certain of the cheaper algaecides can prevent their resulting in foaming.

DIATOMACEOUS EARTH: Also called D.E. A white powder composed of fossilized skeletons of unicellular organisms called diatoms. The skeletons are porous and have microscopic spaces. The powder is added through the skimmer with the pump on and deposits itself on a grid. The powder then becomes the filter medium.

DIATOMACEOUS EARTH FILTER: A filter designed to use diatomaceous earth (D.E.) as the filter medium. The D.E. is added through the skimmer with the pump on, which deposits the D.E. on a grid. The D.E. becomes the filter medium.

DICHLOR: The common name for Sodium Dichloro Isocyanuric Acid. A quick dissolving chlorine compound made up of chlorine and cyanuric acid (stabiliser) and has a pH of 6.9 . Shock treatment with dichlor is not recommended as it may result in overstabilisation and chlorine lock. If dichlor is used, a monthly check of the cyanuric acid level is recommended, to prevent overstabilisation and chlorine lock.

DISINFECT: To kill all pathogenic (disease-causing) organisms.

DISINFECTANT: Chemicals, elements or processes which destroy vegetative forms of microorganisms and other contaminants. Examples are chlorine, bromine, ionisers, ozonators and copper & silver algaecides.

DISSOLVED SOLIDS: See Total Dissolved Solids

DPD: Chemically, NN Diethyl-p-Phenylene Diamine Sulfate. An indicator reagent used to measure free available chlorine (DPD1) and total chlorine (DPD3), bromine, ozone and other oxidizers in water. Far superior to OTO.

DRAIN: A plumbing fitting installed on the suction side of the pump in pools. Also called the main drain, it is located in the deepest part of the pool. Main drains are connected to the pump for circulation, filtration and emptying of the pool.

DRY ACID: Chemically, sodium bisulfate. A dry white crystal that produces acid when added to water. It is used to lower pH and total alkalinity and is safer to handle than liquid acid (hydrochloric acid/ muriatic acid).

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