Pool Terminology

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.

ALGAE
Microscopic plant-like organisms that contain chlorophyll. Algae are nourished by carbon dioxide (CO2) and use sunlight to carry out photosynthesis. It is introduced by rain or wind and grows in colonies, producing nuisance masses. Algae are not disease-causing, but can harbor bacteria, and can be slippery. There are 21,000 known species of algae. The most common pool types are black, blue-green, green and mustard (yellow or drawn). Pink or red-colored algae-like organisms exist but are bacteria and not algae. Maintaining proper sanitizer levels, shocking and superchlorination will help prevent the occurrence of algae.

AUTOMATIC POOL CLEANER
A pool maintenance system that will agitate or vacuum debris from the pool interior automatically.

BACKFLOW
The backing up of water through a pipe in the direction opposite to normal flow.

BACKWASH
The process of thoroughly cleaning the filter by reversing the flow of water through it with the dirt and rinse water going to waste.

BROMIDE
A common term for a bromide salt used to supply bromide ions to the water so they may be oxidized or changed into hypobromous acid, the killing form of bromine. Used as a disinfectant.

BROMINE
A common name for a chemical compound containing bromine that is used as a disinfectant to destroy bacteria and algae in swimming pools and spas. Available as a tablet or as sodium bromide, a granular salt.

BTU
Abbreviation for British Thermal Unit. The amount of heat necessary to raise 1 lb. of water 1 degree Fahrenheit.

CENTRIFUGAL PUMP
A pump consisting of an impeller fixed on a rotating shaft and enclosed in a casing or volute and having an inlet and a discharge connection. The rotating impeller creates pressure in the water by the velocity derived from the centrifugal force.

CHECK VALVE
A mechanical device in a pipe that permits the flow of water or air in one direction only.

CHEMICAL FEEDER
Any of several types of devices that dispense chemicals into the pool or spa water at a predetermined rate. Some dispense chlorine or bromine while others dispense pH-adjusting chemicals.

CHLORINE NEUTRALIZER
A chemical used to make chlorine harmless. Used in test kits to counteract the bleaching effect of the chlorine or bromine in order to increase the accuracy of pool water tests. Sold as chlorine and bromine neutralizer, it is used to destroy excessive amounts of chlorine or bromine so the high levels will not affect swimmers.

CHLORINE
A term used to describe any type of chlorine compound used as a disinfectant in swimming pool and spa water or to kill, destroy or control bacteria and algae. In addition, chlorine oxidizes ammonia and nitrogen compounds (swimmer and bather waste).

COPING
The cap or top lip on the pool or spa wall that provides a finished edge around the pool or spa. It can be formed, cast in place or precast, or prefabricated of extruded aluminum or rigid vinyl. It may also be part of the system that secures a vinyl liner to the top of the pool wall.

CORROSION
The etching, pitting or eating away of the pool or spa or equipment. Caused by improper water balance, misuse of acid or acidic products or from soft water.

COVER, HARD-TOP
A cover used on pools, spas and hot tubs that rests on the lip (coping) of the pool or spa deck – not a flotation cover. Used as a barrier to swimmers and bathers, and for maintenance and thermal protection.

COVER, SOLAR
A cover that, when placed on the water’s surface of a pool, spa or hot tub, increases the water temperature by absorption and transmission of solar radiation; reduces evaporation and prevents windborne debris from entering the water.

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 overdrain on a sand filter. A difuser is also used on a closed-face impeller on a pump to concentrate water flow to the center of the impeller.

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.

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 water to drain to waste but rather connect to the pump for circulation and filtration.

FIBERGLASS
Finespun filaments of glass which are available in a rope or mat form. When used in a process with polyester resins, catalysts and hardeners, can be formed or molded into pools, spas and related shapes.

FILTER
A device that removes undissolved or suspended particles from water by recirculating the water through a porous substance (a filter medium or element). The three types of filters used in pools and spas are sand, cartridge and D.E. (diatomaceous earth).

FILTRATION RATE
The rate at which the water is traveling through the filter, expressed in U.S. gallons per minute (gpm) per square foot of filter area.

FLOW RATE
The quantity of water flowing past a designated point within a specified time, such as the number of gallons flowing past a point in 1 minute – abbreviated as gpm.

GUNITE
A mixture of cement and sand sprayed onto contoured and supported surfaces to build a pool. Gunite is mixed and pumped to the site dry, and water is added at the point of application. Plaster is usually applied over the gunite.

GUTTER
An overflow trough at the edge of the pool through which floating debris, oil and other “lighter-than-water” things flow. Pools with gutters usually do not have skimmers.