Natare Terminology

Equipment, Systems & Construction

a b c d e f g h i j k l m n o p q r s t u v w x y z



    thermoplastic sheet formed into a mold to make a spa or related equipment; it is first heated and then vacuumed onto the mold


    located on the top of the filter, sometimes accompanied by a pressure gauge, the bleeder is opened to release air trapped in the filter


    mechanical device that forces air through holes in the floor, bubbler ring or hydrotherapy jets in a spa


    1. brass or plastic, manually operated valve located at the top of a filter tank for relieving the pressure inside the filter and for removing the air inside the filter (called bleeding the filter)
    2. sometimes called a pressure-relief valve

    device, which agitates or vacuum debris from the walls and floor of the pool automatically

  • Automatic Surge

    device incorporated into a stainless steel perimeter

  • AWS Systems

  • Above-ground (On-ground) pools

    pools that are portable and removable; a frame that is located entirely above ground and can be disassembled

  • Access Equipment

    variety of equipment designed to facilitate entrance and egress from a pool; may include ladders, lifts, steps or boards

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    repositioning of the soil after construction of a pool


    backing up of water through a pipe in the direction opposite to normal flow

  • Backstroke Flags

    colorful vinyl pennants spaced and sized to meet competitive swimming requirements; generally placed five yards (short coarse) or five meters (long course) from the end of the pool; they enable backstrokers to execute a backstroke turn more efficiently by counting their strokes

  • Backwash

    reversing flow of water through the filter to clean the elements and filter medium

  • Backwash Cycle

    time needed to backwash (clean) the filter and its components using a reverse flow of water


    device with a hollowed out ball inside which can be turned with an external handle to decrease or increase flow


    electrical device that produces a continuous rush of air to create the optimal bubbling effect in a spa, hot tub or whirlpool; it is usually plumbed with the hydrotherapy jets or to a separate bubbler ring


    secondary to the filter pump, a booster pump is used to power an automatic pool cleaner such as Polaris or Letro

  • BTU

    1. abbreviation for British Thermal Unit; the amount of heat necessary to raise 1 lb. of water 1 degree Fahrenheit
    2. a unit of measurement for the use of gas by a gas appliance; pool heaters are rated by their consumption
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    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


    plumbing fitting designed to join two pieces of pipe


    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 and thermal protection


    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 wine-borne debris from entering the water


    cover that is secured around the perimeter of a pool, spa or hot tub that provides a barrier to bathers and debris when the pool, spa or hot tub is closed for the season

  • Cover, Thermal

    cover that retains heat and prevents water evaporation


    pool or spa water filter that uses a replaceable porous element made of paper or polyester


    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


    "circuit" of plumbing which continuously carries the water out of the pool, through the pump & filter, and returns it to the pool


    degree of transparency of waterCONDUIT

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  • D. E. FILTER (Diatomaceous Earth Filter)

    filter designed to use diatomaceous earth (D.E.) as the filter medium; the D.E. is added through the skimmer with the pump on, which takes the D.E. and deposits it on a grid; the D.E. then becomes the filter medium



    areas immediately adjacent to a pool or spa that are specifically constructed or installed for use by bathers for sitting, standing or walking


    1. also called D.E.
    2. white poder composed of fossilized skeletons of one-celled organisms called diatoms; the skeletons are porous and have microscopic spaces; the powder is added through the skimmer with the pump on and deposits itself on a grid; the powder then becomes the filter medium
  • Diatomaceous Earth Filter

    see D.E. Filter


    1. porous plate, tube or other device through which air is forced and divided into minute bubbles for diffusion in the water
    2. an over drain on a sand filter
    3. used on a closed-face impeller on a pump to concentrate water flow to the center of the impeller

    1. also called TDS or total dissolved solids
    2. a measure of the total amount of dissolved matter in water; examples are calcium, magnesium, carbonates, bicarbonates, sodium, chlorides and metals; high levels can cause corrosion, colored water or salty taste; maximum level is usually 2500 ppm for pools; maximum level for spas is 1500 ppm over starting level
  • Diving Board

    see springboard

  • Drain (vacuum to waste)

    this useful setting allows you to vacuum large volumes of debris that would either clog the filter or pass through it because of its small size; dirt that is vacuumed passes right out the waste line; it is also the setting of choice when draining the pool or lowering the water level


    1. plumbing fitting installed on the suction side of the pump in pools, spas and hot tubs
    2. 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
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    water that flows out of the pump, on its way through the filter, heating and treating equipment, and returning to the pool; also known as the pressure side


    plumbing fitting shaped at a 90-degree or a 45-degree angle usually made of metal, PVC or plastic


    ornamental shield, flange or border used around a pipe, plumbing fitting, grab rail or light

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

  • Foot Bath

  • Flow Rate

    volume of liquid flowing past a given point in a specific time period, expressed in gallons per minute or hour

  • Flow Meter

    measuring device that determines the gallons per minute of water flow through a pool re-circulation system


    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


    rate of water pumped through a filter, in gallons per minute (gpm)


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

  • Filter Sand

    sharp silica or quartz particles graded for uniform size and used as a filter medium


    graded, rounded rock and/or gravel used to support the filter medium; usually used with rapid-rate sand filters


    device that pulls water from the pool and pushes it through the filter on its way back to the pool


    finely graded material, such as sand, diatomaceous earth, polyester fabric or anthracite coal that removes suspended particles from water passing through it

  • filter latErals

    see underdrain

  • Filter Element

    porous component in the filter tank that removes particles and other suspended wastes from water before its re-circulated back to the pool


    1. operating time between cleaning or backwashing cycles of a filter
    2. amount of time the filter has water flowing through it each day expressed in hours

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


    total surface area of the filter medium that is exposed to the flow of water from the pump, expressed in square feet


    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

    mechanical device for straining suspended waste particles from the pool as water circulates through a porous substance called a filter medium; refers to the complete mechanism including all components; the three types of filters used in pools and spas are sand, cartridge and D.E. (diatomaceous earth)


    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

  • Face Piping

    piping, with all valves and fittings, which is used to connect the filter system together as a unit; this includes all valves and piping necessary for the filter plant to perform the functions of filtering or backwashing, either by the plant as a whole or any unit operating singly

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  • Gelcoat

    colored polyester-resin liquid applied to a mold during the manufacturing of fiberglass pool or spa shells

  • GPD

    gallons per day

  • GPH

    gallons per hour

  • GPM

    gallons per minute


    1. also called hand rail
    2. tubular steel or plastic device that can be gripped by swimmers or bathers for the purpose of steadying themselves; usually located near the steps in the pool

    condition caused by too much copper, not chlorine in the pool water; copper may get into the water by the bad practice of placing trichlor tabs in the skimmer; this acidic product will cause low-pH water, which in turn will dissolve metals in the equipment; the dissolved metal (usually copper) then stains hair, fingernails and, eventually, pool walls; keeping the pH too low or misusing acid can also cause it


    interrupts (de-energizes) the electrical circuit whenever it detects the presence of excess electrical current going to ground (usually 1/40th of a second and 5/1000th of an ampere)

  • Gunite

    concrete and sand mixture sprayed onto a reinforced steel form to create a pool shell; dry mixture of cement and sand is mixed with water at the "gun or spraying device", hence the name


    1. overflow trough at the edge of the pool through which floating debris, oil and other "lighter-than-weight" items flow; pools with gutters usually do not have skimmers
    2. also called a perimeter or recirculation system

    electronic valve in the pool heater that directs gas flow from the meter to the pilot and the burner tray

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    see grab rail


    screen attached to a frame which is then attached to a telepole used to remove large floating debris, such as leaves and bugs, from the water’s surface


    1. 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
    2. set of 8 or 10 ribbed copper tubes that absorb the heat produced below it and transfer it to the water cycling through its tubes

    using a cooling coil, it removes heat from the air while the condenser coil transfers it to the water being cycled through the pump


    fossil-fueled, electric or solar device used to heat the water of a pool, spa or hot tub

  • Hot Tub

    a circular, wooden vessel with the sides and bottom formed separately and joined together by hoops, bands or rods; filled with heated and circulated water


    fitting in the pool or spa on the water return line from the equipment that blends or mixes air and water, creating a high-velocity, turbulent stream of air-enriched water


    force involving built up ground water, which creates upward pressure beneath the pool shell


    fitting(s) installed in the floor of the pool designed to manually or automatically release hydrostatic pressure beneath the pool by allowing ground water into the pool

  • Hydrotherapy Spa

    unit primarily for therapeutic use to ease stress, muscle strains and other physical problems

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  • Influent

    1. water flowing into a filter, pipe, pool, chemical feeder or other space; water going into the pump is called in influent, while water leaving the pump is called the effluent
    2. the water coming into and up to the impeller from the suction lines; these pipes are under vacuum pressure
  • In-ground pools

    are partially or completely installed in the ground


    fitting in the pool or spa on the water return line from the equipment that water returns to the pool


    rotating member of a pump; its action creates the flow of water

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    brand name of a three-way valve, which has simplified pool plumbing


    used in spas to provide additional thrust into the hydrotherapy jets

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    structure used for getting in and out of the pool; a double-access ladder straddles the pool wall of an aboveground pool; an in-pool ladder is located in the pool only


    rubber caps or inserts that protect the pool plaster or vinyl liner from the sharp steel ends of the ladder


    1. elongated, capped plastic nibs at the bottom of a sand filter, which are slotted to allow for water passage while keeping the sand in the filter tank
    2. see also underdrain
  • Leaching

    process of extracting a mineral from plaster pool interiors or tannic acid from wooden hot tubs


    device that attaches to a telepole and a garden hose; pressure from the garden hose creates a suction by which leaves and large debris are sucked into a large mesh bag

  • Leisure Surfacing


    area in a pool or spa that house the underwater light

  • LOAD

    electric device, which consumes energy, placing a load on the source


    see underdrain


    1. influent fitting, typically low on the wall in the deep end of a vinyl liner pool
    2. a cheaper alternative to a main drain
  • Lumina System

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    1. seal behind the impeller that prevents water from running out along the shaft of a motor
    2. also called a pump seal
  • Mechanical Systems

    integrated equipment including filters, piping, valves, pumps, disinfecting units and automatic control systems

  • Membranes


    1. unit of length equal to 1 millionth of a meter
    2. used to describe the pore size of filter media; (sand filters have openings of 25 to 30 microns; cartridge filters have openings of 8 to 10 microns; and D.E. (diatomaceous earth) filters have openings of 1 to 5 microns); a granule of table salt is between 90 to 110 microns
  • Modular System

    cellular hi-rate sand filtration system utilizing an expandable modular cell design for increased flow rates


    1. machine for converting electrical energy into mechanical energy
    2. known as the dry end of the filter pump; it drives the impeller, which moves the water
  • Movable Bulkhead

    a movable end wall that allows multipurpose usage


    1. 4 or 6 position valve combining the functionality of several valves into one unit, revolutionizing pool plumbing
    2. also called a rotary-type backwash valve; water from the pump can be diverted for various functions by merely turning the valve handle; the water may be sent to waste, used for backwashing, bypassing the filter for maximum circulation, for normal filtration, filtering to waste (rinse), or the valve may be closed to not pass water; the pump must be off before changing a valve setting

    see drain


    branch pipe arrangement that connects several input pipes into one chamber or one chamber into several output pipes; a filter manifold connects several input pipes from the filter sept back into one common pipe


    originally a brand name for a white plaster finish coat from 1/8-1/2-inch inch thick applied over the gunite or shotcrete

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    brand name for a thermoplastic resin used in the manufacture of certain pump components and various other pool equipment fittings

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  • On-ground pools

    see above ground pools

  • ORP

    1. exudation reduction potential
    2. measurement of a body of water’s ability to oxidize contaminants; measured with an electrode and an electronic meter
    3. an indication of the sanitizing level or degree of safety from disease in the water; measured in millivolts with the accepted minimum level being 650 mV (millivolt)
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    1. return side of the plumbing
    2. section from the pump impeller toward the pool
  • PVC

    1. polyvinyl chloride
    2. used to make flexible and rigid PVC pipe

    two-position valve used for backwashing sand or DE filters

  • Pump Strainer

    lint and hair trap on the suction side of the pump to remove debris with a minimum of water flow restriction


    1. also called a pump performance curve
    2. graph that represents a pump’s water flow capacity at any given resistance

    volume of liquid a pump is capable of moving during a specified period of time; usually gallons per minute (gpm)

  • Pump

    motor-powered mechanical device that creates pressure and water flow to permit filtration, heating and water circulation; pools usually use a centrifugal-type pump

  • Psi

    pounds per square inch


    used in pool heaters that opens when the flow rate is insufficient for safe heater operation; this disrupts the circuit in the heater, preventing it from firing


    device indicating pressure in a filter system


    organism that causes disease

  • Pressure Differential

    difference in the amount of water pressure being exerted on two parts of a hydraulic system, such as the incoming vs. the outgoing water through a filter


    1. test for the rate of water flow
    2. a test for leaks in plumbing by placing a line in question under pressure and waiting for the pressure to drop

    depositing diatomaceous earth (D.E.) onto the filter grids or elements


    sliding disc assembly that changes valve position in a push-pull valve


    mixture of white cement and white marble dust used as an interior finish, which can be tinted and colored applied to gunite or shotcrete pools or spas


    manually operated faucet or valve for draining liquids or releasing air pressure; air-relief valve on a filter is an example

  • Permanent Medium Filter

    uses sand or other medium that does not require replacement

  • Perimeter System

    see recirculating system

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    quantity of water flowing past a designated point within a specified time period, measured in gallons per minute (gpm)

  • Recirculating System

    1. system of pipes, pumps, filters that allows water to be taken from the pool, filtered, treated and returned to the pool
    2. also called a gutter or perimeter system
  • Recreational Surfacing


    .. A horizontal slot, formed or cut in a concrete, tile, masonry or block wall into which the top edge of Natatec PVC membrane or NataDek flooring or other material can be inserted and anchored.

  • Residential

    pools for home use rather than for public or commercial use

  • reverse circulation

    pool-water circulation system; water is taken from the surface of the pool and returned through inlets at the bottom of the pool

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    black mats of miniature plastic tubes through which water is pumped, absorbing the heat as it passes through; these mats are roof mounted with up and down plumbing connecting it

  • Swimmer Load

    the number of persons in the pool area at any given moment, or any stated period of time


    insoluble solid particles that either float on the surface or are in suspension in the water, causing turbidity


    1. part of a stainless steel gutter that controls the operating level of the pool at quiescent (low or no-use periods) to ensure that adequate in-pool surge is available when swimmers enter the pool
    2. eliminate the need for a surge control tank

    1. large tank constructed near or immediately adjacent to the edge of the pool that incorporates a modulating valve on the main drain to maintain a normal operating level well below the level of the pool in quiescent operation
    2. the difference between the pool level and the operating level in the surge tank is the surge capacity, which is normally required to be approximately 1 to 2 gallons per square foot of pool surface area

    device in a perimeter gutter system that controls the amount of water coming into the gutter from the weir openings in the face of the gutter

  • SPS Systems


    1. also called diving board
    2. recreational mechanism for entering a swimming pool consisting of a semi-rigid board that derives its spring from a fulcrum mounted below the board and attached to the deck
  • SPA

    filtered, hot water vessel with hydrotherapy jets and air induction; can be portable or installed permanently


    the origination of electrical power; the source for a filter pump (load) is probably a timer clock


    see make-up water

  • Solar Heating System

    panels or coils of plastic or metal through which water passes to increase the temperature from the sun’s heat


    water or a liquid containing a high concentration of suspended solids


    1. part of a skimmer that adjusts automatically to small changes in water level to assure a continuous flow of water to the skimmer; the small floating "door" on the side of the skimmer that faces the water
    2. the weir also prevents debris from floating back into the pool when the pump shuts off

    attached to a telescopic pole, a leaf rake is a very useful tool in keeping the pool clean


    removable, slotted basket or strainer placed in the skimmer on the suction side of the pump; beneath the lid, the basket strains debris, as the first line of defense in filtering the water

  • Skimmer

  • SILT

    soil particles having diameters between 0.004 and 0.062 mm


    filter using sand or sand and gravel as the filter medium; the pump diffuses water over the top of the sand bed, and forces it through the sand and into the laterals on the bottom


    mixture of sand and cement sprayed onto contoured and supported surfaces to build a pool or spa; plaster is applied over the shotcrete; shotcrete is premixed and pumped wet to the construction site


    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

  • SAND

    usually refers to the filter medium used by a sand filter; the grade most often specified by filter manufacturers is grade No. 20 with a particle size of 45 to 55 mm

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    mechanical or electrical device that automatically controls the periods that a pump, filter, heater, blower, automatic pool cleaner or other electrical devices are on or off


    1. also called turnover rate
    2. number of times a quantity of water equal to the total capacity of the pool passes through the filters in a stated time; usually in turnovers per day; pool capacity in gallons, divided by pump flow rate in gallons per minute (gpm), divided by 60 minutes in 1 hour, will give hours for 1 turnover
  • TEE


    long-handled aluminum pole, which extends in length to which various pool-cleaning tools, such as brushes or vacuums, can be attached

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    1. lower collection system in a filter, which directs filtered water back toward the pool
    2. distributes water in reverse during backwashing
    3. also called filter laterals or lower collection system

    fixture designed to illuminate a pool or spa from beneath the water’s surface

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    1. one of several types of suction devices designed to collect dirt from the bottom of the pool; some discharge dirt and water into the filters, some discharge to waste, and some collect debris in a porous container, allowing water to return to the pool; some are self-propelled; others must be pushed or pulled across the pool
    2. low-pressure condition created in the suction line
    3. cleaning process of sucking leaves, algae and debris from the pool floor

    device placed in the plumbing line, which restricts or obstructs water flow to create desired hydraulics, or may permit flow in one direction only


    1. fitting or device that consists of a tube constricted in the middle and flared on both ends; a fluid’s velocity will increase and a fluid’s pressure will decrease while passing through the constriction; placing a tube or pipe at the constriction point creates a vacuum; fluid or air can then be drawn in through the tube; a hydrotherapy jet draws air in and mixes it with the water using this principle
    2. increasing water velocity by restricting pipe size

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    1. also called coagulant or flocculants
    2. a chemical compound used to gather (coagulate or agglomerate) or to precipitate suspended particles so vacuuming or filtration may remove them; there are two types
  • WEIR

    see skimmer weir

  • Winterizing

    procedure for protecting pools, spas and hot tubs from freezing conditions; includes physical and chemical protection


    1. also called coagulant or flocculants
    2. a chemical compound used to gather (coagulate or agglomerate) or to precipitate suspended particles so vacuuming or filtration may remove them; there are two types:  inorganic salts of aluminum (alum) and other metals, and water-soluble organic polyelectrolytes
  • WEIR

    see skimmer weir

  • Winterizing

    procedure for protecting pools, spas and hot tubs from freezing conditions; includes physical and chemical protection

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