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

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

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

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

AIR-RELIEF VALVE: (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

AUTOMATIC POOL CLEANER: 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: see Uniwall Systems

BACKFILL: repositioning of the soil after construction of a pool

BACKFLOW: 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

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

BLOWER: 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

BOOSTER PUMP: 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

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

CENTRIFUGAL PUMP: 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

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

CLARITY: degree of transparency of water

CONDUIT: pipe, usually gray pvc or flexible pvc designed to carry wires from a source (i.e. time clock) to a load (i.e. pump motor)

COPING: 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

COUPLING: plumbing fitting designed to join two pieces of pipe

COVER, HARD-TOP: 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, SOLAR: 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, WINTER: 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 

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

DECK SURFACING: see NataDek™

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

DIATOMACEOUS EARTH: (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

DIFFUSER: (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

DISSOLVED SOLIDS: (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

DRAIN: (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

EFFLUENT: 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

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

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