Pool-Speak – Pool Terminology 101
What Those Words & Phrases Mean.

Does pool terminology sound like gobbledygook to you when you are discussing anything about your pool or spa with your pool guy or supplier? Well help is on hand here. Below is an A to Z list of the most common words and terms that are used in the pool industry, with an easy to understand explanation of what they mean to help you along.

Pool alphabet-A
ACID: It might seem odd, but if your pool’s pH balance is off (see pH) you’ll need to add acid to your pool. Acid is a chemical that contains hydrogen, and can balance out the presence of alkaline materials in your pool. But beware: too much acid, and your pool water can corrode metal and be uncomfortable to swim in.

AIR-RELIEF VALVE: A manually-operated brass or plastic valve located at the top of a filter tank that regulates the air pressure inside the filter and removing the air inside the filter (bleeding the filter). Also known as a pressure-relief valve.

ALGAE: Algae is a scientific catch-all term for a variety of microscopic organisms that contain chlorophyll, and have features similar to plants. They’re fairly harmless, but they can drastically change the color of your pool water; and if algae gets thick enough, it can damage your filter. 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).

ALGAECIDE: As its name implies, algaecide is a substance you use to kill algae in your pool. These might be herbicides, or they might be silver or copper compounds. Each type of algaecide tackles a different type of algae, so be sure you know what kind of algae you have before heading to the pool supply store.

ALKALINITY: The opposite of acidity. See total alkalinity (TA) below.

AUTOMATIC POOL CLEANER: A pool maintenance system that will agitate and/or vacuum debris from the pool interior automatically. See also Vacuum below.

Pool Alphabet-B
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.

BLEACH: This is another term for liquid chlorine. It is similar to the bleach used in cleaning laundry, but pool bleach has about three times the concentration of actual chlorine.

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.

pool alphabet-C
CALCIUM CHLORIDE: This is a water-soluble white salt that can be used to alter the hardness of your pool’s water.

CALCIUM HARDNESS: The amount of calcium carbonate in the water. Low calcium hardness (as in “soft” water) can cause etching and corrosion of pool plaster. High calcium hardness can cause scale to form on the interior of the pool surface and cause cloudy water and calcification of filter media.

CARTRIDGE FILTER: There are multiple types of pool filter. A cartridge is the replaceable element of your filter, and it’s generally made of polyester or paper.

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 chemical feeders dispense chlorine or bromine while others dispense pH-adjusting chemicals.

CHLORAMINES: If you don’t have enough chlorine in your pool, the unpleasant compounds the chlorine is meant to destroy will only partially break down. When this happens, chloramines are created, which can smell bad (oddly, they have a strong chlorine smell) and make swimming unpleasant.

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.

CHLORINE NEUTRALIZER: A chemical used to make chlorine harmless. It is 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, chlorine neutralizer is used to destroy excessive amounts of chlorine or bromine so the high levels will not affect swimmers.

CLARITY: This term describes the transparency of your pool water. If your water is not clear, it may be a sign that you have an algae problem.

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 refer to that 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 water spa, increases the water temperature by absorption and transmission of solar radiation; reduces evaporation and prevents windborne debris from entering the water. This can also act as a safety measure when the pool is not in use.

Pool alphabet-D
D E: Diatomaceous Earth is a powder that’s made up of thousands of fossilized diatoms, or single-celled organisms. Because the tiny fossils are porous, they make a perfect material for filtering impurities out of your pool water. DE filters are some of the most effective pool filters on the market.

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.

Pool alphabet-F

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.

Pool alphabet-G
GLASS FIBER: 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. Referred to as fibreglass in some countries.

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 do not normally have skimmers.

Pool alphabet-H
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.

HARD WATER: Water is considered “hard” when it has unacceptably high levels of calcium or magnesium. Hard water can result in less-than-pleasant swimming conditions and a crumbly white buildup on pool fixtures.

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.

Pool alphabet-I
INLET: After your filter cleans your pool water, it passes it back into your pool via the inlet.

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Pool alphabet-LLEAF NET or POLE SKIMMER: You’ve probably seen one of these tools even if you don’t own a pool yet. It’s a net situated at the end of a long pole, used for plucking leaf litter or other floating debris out of the pool.

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.

Pool alphabet-M
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.

Pool alphabet-N
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.

Pool alphabet-O
OXIDIZER: A non-chlorine “shocking” compound that removes or destroys built-up contaminants and chloramines in pool water without raising chlorine levels.
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Pool alphabet-P
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.

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. It is 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, that 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.
Pool alphabet-S
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 that 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 spa, increases the water temperature by absorption and transmission of solar radiation; reduces evaporation and prevents windborne debris from entering the water.
Pool alphabet-T
TOTAL ALKALINITY (TA): This refers to the amount of alkaline material in the water. If TA is too low, pH “bounce” can occur and there will be a tendency towards corrosion. High TA leads to cloudy water, increased scaling and will make it difficult to reduce pH to the ideal level.

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 and “read” 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.

Pool alphabet-V
VACUUM: Device that uses 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. Manual pool vacuums must be operated by a person, and debris is collected in the filter. Automatic pool vacuums plug into the pump and filter system.

VINYL LINER: The vinyl membrane that acts as the container to hold or contain pool water.

Pool alphabet-W
WATER BALANCE: This term is used to describe the interaction of pH, TA and calcium hardness and their overall effect on the pool surface, the pool equipment and the quality of the water. The water must be balanced so that it is neither corrosive nor scaling.

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.