Pool / Spa Industry Terminology


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D. E. FILTER 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 takes the D.E. and deposits it on a grid. The D.E. then becomes the filter medium.

DECKS Those areas immediately adjacent to a pool, spa or hot tub that are specifically constructed or installed for use by bathers for sitting, standing or walking.

DEEP AREAS  Water depths of five feet or greater.

DEFOAMER (chemical related) Also called 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 suds. Most often, the water must be drained and refilled to remove the soaps, oils and other causes of foaming. Shocking and super chlorination may help prevent foaming.

DIATOMACEOUS EARTH Also called D.E. - A white powder composed of fossilized skeletons of one-celled 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.

DICHLOR (chemical related) The common name for sodium dichlor. A fast- dissolving chlorine compound containing chlorine and cyanuric acid (stabilizer or conditioner). It has a neutral pH and is quick-dissolving, so it can be used for regular chlorination or super chlorination.

DIFFUSER A porous plate, tube or other device through which air is forced and divided into minute bubbles for diffusion in the water. A diffuser can also be an over-drain on a sand filter. A diffuser is also used on a closed- face impeller on a pump to concentrate water flow to the center of the impeller.

DISINFECT (chemical related) To kill al pathogenic (disease-causing) organisms.

DISSOLVED SOLIDS (chemical related) Also called TDS or total dissolved solids - A measure of the total amount of dissolved matter in water. Examples are calcium, magnesium, carbonates, bicarbonates, sodium, chlorides and metals. High levels can cause corrosion, colored water or salty taste. Maximum level is usually 2500 ppm for pools. Maximum level for spas is 1500 ppm over starting level.

DIVERTER VALVE A plumbing fitting used to change the direction or redirect the flow of water. Some diverter valves are used on pool/spa combinations to allow the use of the spa and then switch the flow back to the pool. A brand name diverter valve is called an Ortega valve, which is sometimes used to describe a diverter valve.

DIVING BOARD A recreational mechanism for entering a swimming pool, consisting of a semi-rigid board that derives its spring from a fulcrum mounted below the board and attached to the deck.

DPD (chemical related) An indicator reagent used for the determination of free and total chlorine, bromine, ozone and other oxidizers in water. Better than using OTO for chlorine because it measures free chlorine.

DRAIN This term usually refers to a plumbing fitting installed on the suction side of the pump in pools, spas and hot tubs. Sometimes called the main drain, it is located in the deepest part of the pool, spa or hot tub. It is not a drain, such as a drain on a kitchen sink. Main drains do not allow the to drain to waste but rather connect to the pump for circulation and filtration.

DRY ACID (chemical related) Chemically, sodium bisulfate. A dry white crystal that produces acid when added to water. It is used for lowering pH and total alkalinity. Safer to handle than muriatic acid.

DSI (gas heater related) DSI stands for direct spark ignition.

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