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.
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.
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 hot tub water or to kill, destroy or control bacteria and algae. In addition, chlorine oxidizes ammonia and nitrogen compounds cause by swimmers.
COPING: The cap or top lip on the pool or hot tub 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 hot tub or equipment. Can be caused by improper water balance, misuse of acid or acidic products or from soft water.
COVER, SOLAR: A cover that, when placed on the water's surface of a pool, hot tub or hot tub, increases the water temperature by absorption and transmission of solar radiation; reduces evaporation and prevents windborne debris from entering the water.
D.E.: Diatomaceous Earth — a porous substance used in certain types of pool filters.
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 hot tub 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, hot tub or hot tub. It does not function like a 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.
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 and spas.
FILTER: A device that removes dissolved 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 — 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.
POOL COVER, (HARD-TOP): A cover used on pools, spas and hot tubs that rests on the lip (coping) of the pool or hot tub deck ; not a flotation cover. Used as a barrier to swimmers and bathers and for maintenance and thermal protection.
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 hot tub 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 listed in gallons per minute or gpm.
PUMP CURVE: Also called a pump performance curve. A graph that represents a pump's water flow capacity at any given resistance.
pH: Abbreviation for Potential Hydrogen. Indicates the level of acidity or alkalinity of water on a scale ranging from 0-15. A low pH can cause etched plaster, metal corrosion and eye irritation. A high pH can cause scale formation, chlorine inefficiency and eye irritation. The ideal range for pH in swimming pools is typically 7.4 to 7.6.
SANITIZERS: Chemical compounds designed to kill bacteria, algae and other living organisms. Also protects water from the effects of the sun.
SHOCK TREATMENT: The practice of adding significant amounts of an oxidizing chemical -- (usually non-chlorine oxidizers, such as sodium persulfate or potassium peroxymonosulfate) -- to the water to destroy ammonia and nitrogen compounds caused by swimmers, the environment and/or weather.
SKIMMER: A device installed through the wall of a pool or hot tub that is connected to the suction line of the pump that draws water and floating debris in the water flow 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, which is designed to trap floating debris in the water flow from the surface without causing flow restriction.
SOLAR COVER: A cover that, when placed on the water's surface of a pool, hot tub or hot tub, increases the water temperature by absorption and transmission of solar radiation; reduces evaporation and prevents windborne debris from entering the water.
TEST KIT: An apparatus or device used to monitor specific chemical residuals, levels, constituents or demands in pool or hot tub water. The most common pool and hot tub water tests are: pH, total alkalinity, free available chlorine, water hardness, cyanuric acid, iron and copper.
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.