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: see NataDek

REGLET: 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

SAND FILTER: 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

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

SEPTUM: 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

SHOTCRETE: 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

SILT: soil particles having diameters between 0.004 and 0.062 mm

SKIMMER: device in the pool wall that continuously directs debris and surface water to the filter; a hand skimmer can be used manually to collect leaves and other large floating debris from the water’s surface

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

SKIMMER WEIR: (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

SLURRY: water or a liquid containing a high concentration of suspended solids

SOLAR HEATING SYSTEM: panels or coils of plastic or metal through which water passes to increase the temperature from the sun's heat

SOLAR SYSTEM: 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

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

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

SPRINGBOARD: (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

SPS SYSTEMS: see Uniwall Systems

SURGE CONTROL GATE: 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

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

SURGE CONTROL WEIR: (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

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

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

TEE: plumbing fitting used in the shape of a “T” used to connect pipes

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

TIME CLOCK: 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

TURNOVER: (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 

UNDERDRAIN: (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

UNDERWATER LIGHT: fixture designed to illuminate a pool or spa from beneath the water's surface 

UNIWALL SYSTEMS: stainless steel construction systems for aquatic environments; AWS, SPS and Lumina systems are available

VACUUM: (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

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

VENTURI: (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

VINYL LINER: see Natatec® Membrane Systems

PVC MEMBRANE LINER: see Natatec® Membrane Systems

WATER CLARIFIER: (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