Pool / Spa Industry Terminology


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FIBERGLASS Fine spun 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 non-dissolved or suspended particles from water by re-circulating 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).

FILTER AID (chemical related) A chemical compound added to the water or to the filter that allows the existing filter to become more efficient. Examples are alum, water clarifiers and D.E. (diatomaceous earth).

FILTER AREA The total surface area of the filter medium that is exposed to the flow of water from the pump, expressed in square feet. Examples are: a 36 sq.ft. (also 36 ft2) D.E. filter and a 100 sq.ft. (also 100 ft2) cartridge filter.

FILTER CARTRIDGE A replaceable porous element made of paper or polyester used as the filter medium in cartridge filters.

FILTER CYCLE The operating time between cleaning or backwashing cycles of a filter. Also the amount of time the filter has water flowing through it each day expressed in hours.

FILTER ELEMENT A device within a filter tank designed to trap suspended solids as water flows through it from the pool or spa.

FILTER MEDIUM The material used in the filter to trap suspended dirt particles as the water is flowing through it. The polyester or paper used in making a cartridge filter element. The sand used in a sand filter. The D.E. (diatomaceous earth) used in a D.E. filter.

FILTER POWDER A common name for diatomaceous earth (D.E.), used as the filter medium in a diatomaceous earth filter.

FILTER ROCK Graded, rounded rock and/or gravel used to support the filter medium. Usually used with rapid-rate sand filters.

FILTER SEPTUM That portion of the filter element consisting of cloth, wire screen or other porous material on which the filter medium or filter aid is deposited. The nylon grid on a D.E. filter is the septum.

FILTER, SAND A type of filter media composed of hard, sharp silica, quartz or similar particles with proper grading for size and uniformity. The most common grade used is No. 20 in sand filters.

FILTRATION FLOW  The design rate of flow, expressed in U.S. gallons per minute (gpm) or gallons per hour (gph), through the filter system installed per manufacturer's instructions with a new, clean filter medium.

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 effective filter area.

FIREMAN'S SWITCH A mechanical switch located inside the time clock, which opens a circuit and shuts off the heater 10 or 15 minutes prior to shutting off the water circulation pump, allowing the heater to cool down. This helps reduce lime buildup in the heat exchanger.

FLOC (chemical related) (also see flocculation) - The clump or tuft formed when suspended particles combine with a flocculating agent.

FLOCCULATING AGENT (chemical related) Also flocculant - A chemical substance or compound that promotes the combination, agglomeration, aggregation or coagulation of suspended particles in the water.

FLOCCULATION (chemical related) The combination, agglomeration, aggregation or coagulation of suspended particles in such a way that they form small clumps or tufts (called floc).

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.

FOAM (chemical related) A froth of bubbles on the surface of the water. Usually comes from soap, oil, deodorant, hair spray, suntan oil, etc., that is shed into the water as swimmers enter.

FREE AVAILABLE CHLORINE  (chemical related) The amount of free chlorine in the pool or spa water that is available to sanitize or disinfect the water. Sometimes called residual or available chlorine.

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