AIR-RELIEF VALVE: A manually-operated brass or plastic valve located at the top of a filter tank for relieving the pressure inside the filter and removing the air inside the filter (bleeding the filter). Also known as a pressure-relief valve.
ALGAE: Microscopic plant-like organisms that contain chlorophyll. Algae is nourished by carbon dioxide (CO2) and use sunlight to carry out photosynthesis. It can be introduced by rain or wind and grows in colonies, producing nuisance masses. Algae can harbor bacteria and can be slippery. There are thousands of known species of algae. The most common types of algae found in pools are black, blue-green, green and mustard (yellow or drawn).
ALGAECIDES: Chemical compounds designed to kill, prevent and control algae.
AUTOMATIC POOL CLEANER: A pool maintenance system that will agitate and/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.
BALANCERS: Chemical compound designed to prevent corrosion and staining by balancing the pH, total alkalinity and calcium hardness in pool water.
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: A device that dispenses chemicals into pool or hot tub 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.
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 — also known as gallons per minute or gpm.
GPM: Abbreviation for “gallons per minute.”
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.
HAND SKIMMER: A screen attached to a frame which is then attached to a telescopic pole used to remove large floating debris, such as leaves and bugs, from the water's surface.
HEAT EXCHANGER: A device located inside the heater providing for the transfer of heat from the heat source to the water. This is usually a series of metallic tubes with fins located just above the flames.
HEATER: A fossil-fueled, electric or solar device used to heat the water of a pool, hot tub or hot tub.
LINER: Also called a vinyl liner. The vinyl membrane that acts as the container to hold or contain the water in some types of pools.
MAIN DRAIN: A plumbing fitting installed on the suction side of the pump in pools, spas and hot tubs. Sometimes simply referred to as the drain, it is located in the deepest part of the pool, hot tub or hot tub. It does not function like the drain on a kitchen sink. Pool main drains do not allow the water to drain to waste but rather connect to the pump for circulation and filtration.
NEUTRALIZER: A chemical used to make chlorine or bromine 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.
OXIDIZER: A non-chlorine shocking compound that removes or destroys built-up contaminants and chloramines in pool water without raising chlorine levels.
TEST STRIPS: Small plastic strips with pads attached that have been impregnated with reagents that can be used to test pool water for residuals, levels, constituents or demands. The strips are usually dipped in the water, and the resulting colors of the pads are compared to a standard set of colors to determine concentration.
TURBIDITY: The cloudy condition of the water due to the presence of extremely fine particles in suspension that cannot be trapped by the filter because they are too small. Adding a clarifier, such as an organic polymer or alum, will coagulate the particles and make the filter more efficient.
VACUUM: Devices that use suction to collect dirt from the bottom and sides of a pool or spa. Most common is a vacuum head with wheels that attaches to a telepole and is connected to the suction line, usually via the opening in the skimmer. Pool vacuums must be operated by a person, and debris is collected in the filter.
VINYL LINER: The vinyl membrane that acts as the container to hold or contain pool water.
WATER CLARIFIER: Also called coagulant or flocculant . A chemical compound used to gather (coagulate or agglomerate) or to precipitate suspended particles so they may be removed by vacuuming or filtration. There are two types; inorganic salts of aluminum (alum) and other metals or water-soluble organic polyelectrolytes.
WEIR: The small floating "door" on the side of the skimmer that faces the water over which water flows on its way to the skimmer. Adjusts automatically to small changes in water level to assure a continuous flow of water to the skimmer. The weir also prevents debris from floating back into the pool after the pump shuts off. Also known as a skimmer weir.