AIR-RELIEF VALVE A brass or plastic manually operated valve at the top of a filter tank for relieving pressure and removing air inside the filter (called bleeding the filter). Sometimes called a pressure-relief valve.
AUTOMATIC POOL CLEANER A pool maintenance system that automatically agitates or vacuums debris from the pool interior.
BACKFLOW The backing up of water through a pipe in a 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 as a disinfectant.
BROMINE A common name for a chemical compound used as a disinfectant BTU Abbreviation for British Thermal Unit, the amount of heat necessary to raise 1 pound of water by 1 degree Fahrenheit.
CENTRIFUGAL PUMP A pump consisting of an impeller fixed on a rotating shaft, 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 A device that dispenses 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 increase the accuracy of pool water tests.
CHLORINE A term used to describe any type of chlorine compound used as a disinfectant in swimming pool and spa water.
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.
COVER, HARDTOP 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, energy efficiency 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 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.
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.
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 Fine-spun filaments of glass available in a rope or mat form. When used in a process with polyester resins, catalysts, and hardeners, fiberglass 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-thanwater" things flow. Pools with gutters usually do not have skimmers.
HAND SKIMMER A screen attached to a frame, which is then attached to a tele pole, used to remove large floating debris such as leaves from the water's surface.
HARD TOP COVER 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, energy efficiency and thermal protection.
HEAT EXCHANGER A device located inside the heater providing for the transfer of heat from the heat source to the water.
HEATER A fossil-fueled, electric or solar device used to heat the water of a pool, spa or hot tub.
LINER Also called vinyl liner - The vinyl membrane that acts as the container to hold or contain the water.
MAIN 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 drain and 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.
POOLSCAPE A poolscape is a well-integrated living environment combining a quality pool with the functional and aesthetic considerations of the home and landscape.
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 is used for pools, spas and hot tubs.
PUMP CAPACITY The volume of liquid a pump is capable of moving during a specified period of time. This is usually gallons per minute (gpm).
PUMP CURVE Also called a pump performance curve - A graph that represents a pump's water flow capacity at any given resistance.
PUMP STRAINER BASKET Sometimes called a "hair and lint trap," the pump strainer basket is a device placed on the suction side of the pump, which is designed to trap debris in the water flow without causing much flow restriction.
pH or POTENTIAL HYDROGEN Indicates the level of acidity or alkalinity of water on a scale ranging from 0-15. The ideal range for pH in swimming pools is 7.4 to 7.6.
SKIMMER Installed through the wall of a pool or spa and connected to the suction line of the pump, this device draws water and floating debris from the surface without causing much flow restriction.
SKIMMER BASKET A removable, slotted basket or strainer placed in the skimmer on the suction side of the pump and designed to trap floating debris in the water flow from the surface without causing much flow restriction.
SOLAR COVER 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.
VACUUM Any number of devices that use suction to collect dirt from the bottom and sides of a pool or spa.
VINYL LINER A vinyl membrane that acts as a container to hold or contain the water in a pool. WATER CLARIFIER A chemical compound used to gather or to discharge particles so they may be removed by vacuuming or filtration.
WEIR Also called a skimmer weir, the weir (pronounced "WEER") adjusts automatically to small changes in water level to assure a continuous flow of water to the skimmer and prevent debris from floating back into the pool after the pump shuts off. It consists of a small floating "door" on the side of the skimmer facing the water over which water flows on its way to the skimmer.