A Division of Outdoor Systems Inc.
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Destination Pools

Pool Terminology

Acid: A liquid or dry chemical used to lower the pH and/or alkalinity of pool or spa water.

Acid Wash: A procedure using an acid solution to clean an interior surface of a pool with subsequent neutralization of the acid.

Air Blower: A device that produces a continuous flow of air.  

Algae: Minute plant life growing in water in the presence of sunlight and carbon     dioxide.

Anti-vortex Drain Cover: A plate or cover that is affixed to the main outlet of a       swimming pool or spa that prevents a vortex from forming as water passes       through to the main outlet.

Backfilling: Filling space between pool shell and sides of excavation with dirt.

Backwash: Process of running water through a filter opposite the normal direction of flow to flush out contaminants.

Balance: The term in water chemistry to indicate that when measuring all               components together, the water is neither scaling nor corrosive.

Ball Valve: A device utilizing a ball-shaped diverter to partially or totally obstruct     the flow of water.  

Bleeder Valve: A device that allows air to be vented from a system.

Blower: An electromechanical device that generates air pressure to provide spa    jets and rings with bubbles.  

Bond Beam: Reinforced masonry units designed to resist horizontal forces.

Bonding (electrical): The joining of metallic parts to form an electrically                   conductive path, which will ensure electrical continuity.

Booster Pump System: A pump that is completely independent of the filtration       and heating system.  Used to provide support for hydrotherapy jets, cleaning         systems and gas chlorinators or special water features.
Break in Grade: Occurs when the slope of the pool floor changes to a greater        slope.

BTU: British Thermal Unit. A unit of measurement used to define the capabilities   of heaters.  One BTU is capable of raising the temperature of one pound of water by one degree Fahrenheit.  

Bull Nose: A brick or stone with a rounded corner.

Cantilever: A projecting beam supported only at one end.

Cartridge: Disposable element containing filtering media and used in some pool     filters.

Cartridge Filter: A filter that utilizes a porous element that acts as a filter medium.


Check Valve: A valve that permits flow of water or air in only one direction                        through a pipe.

Chlorine: A substance used to sanitize water by oxidizing (killing) bacteria;             generally available in liquid, solid (tablets or sticks), and granular form.

Circuit Breaker: A device designed to open and close an electrical circuit               manually, and to open a circuit automatically at a predetermined over current          level, thus providing protection to the wiring and electrical components.

Circulation System: An arrangement of mechanical equipment and/or                    components designed to ensure even distribution of heat, chemicals, and                   filtration of water throughout the pool.  Includes filters, heaters, pumps,                        chlorinators, piping, inlets, drains, skimmers and other appurtenances. 

Coping: The cap on the wall that provides a finishing edge around the pool/spa.     Can be formed, cast in place, precast, brick, stone, or pre-fabricated from metal    or plastic material. 

Cove: The radius that joins the floor and wall of a pool/spa.

Crack (structural): A break or split which weakens the structural integrity of the     pool.

Decks: Those areas immediately adjacent to or attached to a pool or spa that are specifically constructed or installed for sitting, standing, or walking.  Generally   made of concrete, wood, or masonry.

Deep Area: Water depth areas exceeding five feet (5').

Diatomaceous Earth (DE): A white, powdery substance composed of tiny              prehistoric skeletal remains of algae (diatoms), used as a water filtration media in DE filters. 

Diatomaceous Earth (DE) Filter: Pool filter using DE as filtering method.

Diverter: Plastic or bronze adapter pipe that fits into a skimmer port to facilitate connection of a vacuum hose.  The diverter can divert all suction to the skimmer, closing off the main drain or vice versa.

Erosion: 1. Act of destroying or dissolving by slow disintegration or wearing away.  2. In an erosion feeder, it is the way water dissolves the chemical being fed.  

Etching: Corrosion of a surface by water that is acidic or low in total alkalinity or    hardness.

Evaporation: Conversion of liquid molecules into vapor.

Feet of Head: The resistance in a hydraulic system based on the equivalent to       the height of a column of water that causes the same resistance (100 feet of            head equals 43 pounds per square inch). The total dynamic head in the sum of all resistances in a complete operating system.

Filter: Device for removing suspended particles from pool water.

Filter Cycle: Time of filter operation between backwashes.

Filter Element: A device within a filter tank designed to entrap solids and conduct water to a manifold, collection header, pipe, or similar conduit and return it to the    pool, spa, or hot tub.  A filter element usually consists of a septum and septum    support or a cartridge.

Filter Media: Fine-grain materials in filter trap matter suspended in pool water.

Flow Rate: The volume of liquid flowing past a given point in a specified time        period.  Usually expressed as U.S. gallons per minute (gpm) or gallons per hour             (gph). 

GPD: Gallons per day.

GPH: Gallons per hour.

GPM: Gallons per minute.
Hardness: Also called "calcium hardness". The amount of dissolved minerals         (mostly calcium and magnesium) in a body of water. In unbalanced water, high            levels cause scale and low levels corrode surfaces and equipment.

Heater: A fossil-fueled, electric or solar device to heat the water of a pool or spa.

Hydrotherapy Jet: A fitting that blends air and water creating a high-velocity           turbulent stream of air-enriched water.

Impeller: The rotating vanes of a centrifugal pump; its action creates the flow of    the water.

Influent: The water entering a filter or other device.

Jets: See Hydrotherapy Jets.

Manifold: A pipe with several openings for making multiple corrections.

Muriatic Acid: A dilute solution of hydrochloric acid used to lower alkalinity and clean masonry surfaces.

O-Ring: Thin rubber gasket used to create a waterproof seal in certain plumbing    joints or between two parts of a device, such as between the lid and the strainer        on a pump.

Overflow System: Refers to removal of pool/spa surface water through the use of overflows, surface skimmers, and surface water collection systems of various       design and manufacture.

pH: Measure of acidity or alkalinity of water; pH of 7 is neutral, below 7 is acidic,   and above 7 is alkaline.

PPM: Parts per million (in a pool, parts of a chemical or mineral per million parts   of water, by weight).

Plaster: A type of interior finish (a mixture of white cement and aggregate , which             will accept a tint of color) which is applied to a concrete pool or spa. Also called          Mar-cite or Marblite.

PSI: An abbreviation for pounds per square inch.

Pumice: A natural soft, abrasive stone substance (similar to lave rock) used to clean pool tiles.

Pump: A mechanical device, usually powered by an electric motor, which causes             hydraulic flow and pressure for the purpose of filtration, heating and circulation of pool and spa water.  Typically, a centrifugal pump design is used for pool and     spas.

PVC: Polyvinyl chloride is thermoplastic resin commonly used for pool piping and plumbing components.

Reinforcing Bar (Rebar): Steel bars embedded in concrete to increase its ability    to withstand bending and stretching.

Return Inlet: The aperture or fitting through which the water under positive            pressure returns into a pool or spa.

Sand Filter: Pool filter using sand as filtering medium.

Scale: The precipitate that forms on surfaces in contact with water when the         calcium hardness, or pH, or total alkalinity levels are too high.

Screed: In cement masonry flatwork, the wood or metal straightedge used to        strike off or level newly placed concrete.

Shotcrete: A mixture of cement and sand, applied onto contoured and supported   surfaces to build a pool or spa.  Shotcrete is premixed and pumped wet to the construction site.

Shocking: See Super-chlorination.

Skimmer: A part of the circulation system that removes debris from the surface of the water.  Through-wall: A device installed in the wall of an inground pool or spa           or aboveground/onground pool that permits the continuous removal of floating           debris and surface water to the filter.              Over-the-wall: A device installed             over the wall of an aboveground/on-ground pool that allows for continuous             removal of debris and surface water to the filter.

Slope: An inclined surface.

Strainer Basket: Device in skimmer and input side of pump used to catch large     pieces of debris in pool water.

Suction Outlet: The aperture or fitting through which the water under negative        pressure is drawn from the pool or spa.

Super-chlorination: Periodic application of extremely high levels of chlorine in (in   excess of 3 ppm) to completely oxidize any organic material in a body of water         and leave a substantial chlorine residual. Also called "shocking".

Swimming Load: Number of people using pool at a given time.

Test Kit: A device used to monitor specific chemical residual or demands in pool   or spa water. 

Three-Port Valve: A plumbing fitting used to divert flow from one direction into two other directions. 
Time Clock: A mechanical device that automatically controls the periods that a     pump, filter, heater, blower and other electrical devices are on.

Total Dynamic Head: See Feet of Head.

Turnover Rate: Number of times all the pool water passes through filter in a given time period.

Underwater Light: A fixture designed to illuminate from beneath the water              surface.                         Wet niche light: A watertight and water cooled light unit             placed in a submerged niche in a pool, spa, or hot tub wall and accessible only           from the pool.                                                                             Dry niche light: A     light unit placed behind a watertight window in the pool, spa, or hot tub wall.

Valve: Any device in a pipe that will partially or totally obstruct the flow of water     (such as with a ball, gate, or glove valve)

Waterline: The waterline shall be defined in one of the following ways:                                           Skimmer System: The waterline shall be at the midpoint of the operating range of the skimmers when there are no users in the pool or spa.                                                
•            Weir: The barrier in a skimmer over which water flows.  A floating

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