GLOSSARY OF SWIMMING POOL TERMS
The text of these Standards refers to and explains many of the terms used in
connection with the swimming pool construction and installation. The following
glossary is included however to give a useful non-technical reference to terms in
common use.
AIR BLOWER
A mechanical device for inducing air into ducting.
AIR SCOURER
A device operated pneumatically to break up, lift up and help cleanse the sand bed
and flocculating agent in the sand filters by agitating the bed on backwash. It also
reduces the backwash time, and consequently the backwash water required.
AIR INDUCTION
A system whereby air is induced into ducting and released into the water through
small orifices.
ALGAE
Minute plant forms which can turn pool water cloudy and discoloured.
ALGICIDE
A chemical compound which destroys or controls algae growth.
ALUM
Traditional name for a flocculent chemicals used in conjunction with slow rate
sand filters. Aluminium sulphate is the correct chemical name.
AMPEREMETRIC CELL
An electronic device for measuring the current produced in water due to the
presence of oxidising agents such as bromine, chlorine and ozone.
ANTIVORTEX FITTING
A cover for a suction fitting which is designed to minimise the formation of
vortices and the risk of entrapment of parts of the human body.
AUTOMATIC CONTROLLER
An electronic system to maintain correct disinfection and/or pH level. A chart
recorder may be incorporation to give a permanent and continuous record of these
parameters.
BACKWASH
The process of reversing water flow to clean a filter and to restore it to the normal
clean running condition of filtering where there is minimum resistance to flow
through the media.
Cleaning of filtration plant by reversing the flow of water through the filter bed
and discharge the waste to drain.
BACKWASH CYCLE
The operating time, after the filter cycle, required to completely clean the filter.
BACKWASH PIPING
The pipe extending from the backwash outlet of the filters to a terminus at the
point of disposal.
BACKWASH RATE
The rate of application of water through a filter during the cleaning cycle
expressed in capacity per minute per effective filter surface area.
BALANCE TANK
Tank filled in circulation system of overflow (level deck) pools and spas to balance
water displaced by bathers and to provide additional water volume in heavy use
situations.
BALANCE WATER
A water which is neither corrosive nor scale forming.
See also Langelier Index.
BALANCE WATER INDEX
Index applied to pool water to asses whether it has corrosive or scale forming
tendencies. The equation used to calculate the index takes into account the pH,
alkalinity, calcium hardness and temperature of the water. See also Langelier
Index.
BAR
A partial unit of pressure (see definition of pressure units below) in the SI (Systems
International) system and equals 100,000 pascals. One bar equals 98.8% of one
standard atmosphere, and for practical purposes can be considered to equal one
standard atmosphere.
BIOCIDE
A compound which destroys bacteria. Term usually applied to formulations based
on organic compounds.
BODY FEED
The continuous addition of small amounts of filter aid ducting the operation of a
diatomaceous earth filter.
BOOSTER PUMP
For pumping water at high pressure, normally sized for maximum performance
through hydrojets.
BREAKER OF DEFLECTOR PLATE
A plate at the inlet of a filter tank position so that the incoming water hits it, and
loses its momentum. This prevents the water jet scoring a hole in the sand bed.
See Distributor (Top or Bottom).
BROMINE
Chemical element with similar chemical properties to chlorine and used as a pool
water disinfectant.
- free bromine
- combined bromine
- total bromine
- bromine demand
- bromine residual
Bromine dissolved in the water to form
hypobromous acid.
Bromine which has reacted with nitrogenous
impurities to form bromamines.
The total sum of free and combined
bromine in the water. Both free and combined
bromine are powerful disinfectants.
The amount of bromine used up when a dose of
bromine is added to pool water by reacting with
impurities and pollution.
The amount of bromine remaining in the pool
water after satisfying the bromine demand.
BROMOCHLORODIMETHYLHYDANTION (BCDMH)
A bromine based disinfectant compound usually available in stick or tablet form.
BROMAMINES
A number of bromine ammonia compounds exhibiting sanitising properties
similar to hypobromous acid (HOBr)
BROMINATOR
A dispensing device for feeding bromine into a spa pool's recirculating system.
CAGE OF SAFETY
Area of water of sufficient size and depth within the deep end of the pool
prescribing minium dimensions for normal deck level diving with safety. See also
Diving Area.
CARTRIDGE FILTER
See Filter Cartridge.
CARTRIDGE
A replaceable porous element, through which water is passed for filtration. See
filtration Cartridge.
CHLORINATION
The process of treating pool water with chlorine. Chlorine can be added to pool
water in a variety of commercially available forms as gas, solutions or solids.
CHLORINE
Chemical element widely used for swimming pool water disinfection.
- free chlorine
- combined chlorine
- total chlorine
- chlorine demand
- chlorine residual
- breakpoint chlorination
- marginal chlorination
Chlorine dissolved in water to form
hypochlorous acid.
Chlorine in this form
destroys bacteria and reacts with pollutants
most rapidly.
Chlorine which has reacted with nitrogenous
impurities in the water to form chloramines.
Chlorine in this form reacts only slowly with
bacteria and other micro-organisms.
The total sum of the free and combined
chlorine in the water.
The amount of chlorine which is used up when
a dose of chlorine is added to pool water by
reacting with impurities and pollution.
The amount of chlorine remaining in the pool
water after satisfying the chorine residual can be
expresses as free chlorine residual, combined
chlorine residual or total chlorine residual.
A process of chlorination whereby a free
chlorine residual is maintained in the water and
the combined chlorine residual is kept as low as
possible. This is the form of chlorination which
should be used for swimming pool treatment.
A form of chlorination whereby a
combined chlorine residual only is maintained
in the water. This form of chlorination is not
now used for swimming pool treatment.
CHLOROISOCYANURATES
Chlorine based disinfectant compounds which are available in granular and tablet
form. Sometimes referred to as stabilised chlorine granules or tablets. These
compounds release both chlorine and cyanuric acid in the pool water.
CHLORAMINES
See Combined Chlorine.
CIRCULATION SYSTEM
The complete water flow arrangement of fittings, pipework and equipment.
COAGULANTS
See Flocculation
COPING
Perimeter edging surrounding a pool.
CORROSION RESISTANT MATERIAL
A material with exceptional resistance to the corrosion factors to which it os
subjected.
CROSS CONNECTION
An unprotected connection between a domestic water system and any pool or
other non-potable water whereby backflow to the domestic system could not
occur. Appropriate protection may be air gaps, non-return valves or other
methods.
CUP ANCHORS
A flush fitting which is set up into the pool walls during construction to enable the
fixings of racing lines or other devices.
CYANURIC ACID
A chemical compound which reduces the loss of chlorine caused be sunlight
attack. It is said therefore to stabilise the chlorine residual. Often referred to as
stabiliser or conditioner.
DATUM
A prescribed, fixed starting point from which levels and lengths, depths and
heights may be measured accurately.
DECKING
Hard surfaced surround to a pool.
DECK LEVEL
Pools where the water level is equal to or just below the deck surround.
DECK LEVEL OVERFLOW SYSTEM
A system with perimeter overflow channels for the removal of surface water
forming a part of the recirculation system.
D E FILTER
Areas surrounding Spas which are specifically constructed and installed for use by
bathers.
DESIGN RATE OF FLOW OR DESIGN FILTER RATE
The average rate of flow in a system which is used for design calculations. (usually
the flow in volume per minute divided by the effective filter surface area).
DISINFECTION
The destruction of bacteria and micro-organisms to a level not normally
considered harmful to health.
DISTRIBUTOR (Top or Bottom)
The device in a filter designed to divert the incoming water to prevent erosion of
the filter media. See Breaker Plate.
DIVING AREA
Area of the pool designed for diving (note: diving areas are defined in detail in
various other standards, such as ASA and FINA regulations etc).
DIVING BOARD
A board designed to simulate spring action. Typically a non-rigid board used for
recreational diving as opposed to competitive diving.
DIVING STAND
Any stand or supporting device for a spring board or diving board.
DPD
A chemical reagent used in pool water test kits to measure the chlorine, bromine
and ozone residuals in the water. Normally supplied in the form of tablets.
DRAIN
An outlet in the Spa for the purpose of emptying.
DRAINAGE
System to carry away surplus water particularly external to the pool shell to lower
pressure and flotation.
EFFLUENT
The outflow of water from a filter or other device.
ELECTROLYSIS
Decomposition of metal due to flow of electrical current.
EROSION FEEDER
A mechanical device to contain solid disinfectant through which some of the
circulation water passes.
FACE PIPEWORK OR BATTERY
The 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.
FILTER
A device that separates particulate matter from water by circulating through
porous media.
FILTER AID
A chemical used to agglomerate suspended particulate matter in the water thus
aiding their removal by the filter.
FILTER ROCK
Graded, rounded rock and/or gravel, used to support filter media.
FILTER SAND
A type of filter media composed of hard sharp silica, quartz, or similar particles
with proper grading for size and uniformity.
FILTER SEPTUM
That part of the filter element consisting of cloth, wire screen or other porous
material on which the filter cake is deposited.
FILTER, VACUUM (or suction)
A filter which operates under a vacuum or from the suction side of a pump.
FILTRATION
The removal of suspended solids from water by passing it through a bed of
insoluble filter media.
FILTRATION RATE
The rate of filtration of water in a given time, ie cubic metres per square metre of
effective filter area per hour (or gallons per square foot of effective filter area per
hour).
FLOC
A gelatinous layer formed on the surface of the sand to aid filtration.
FLOCCULENT
A chemical compound which gathers fine particles together and facilitates their
removal by the filtration system thus improving pool water clarity.
FLOW UNITS
In the SI units, flow rate of a liquid along a pipe is given in cubic metres per
second. For most practical purposes, this flow far exceeds that met in swimming
baths, so that the flow is given in litres or gallons per second. The conversion is
1m³ = 1000 litres/second = 220 gallons/second.
FLUE (Skimmer Flue)
The tapered orifice in the pool wall into which surface skimmers are affixed.
FLOOR SLOPE
The slope in the pool floor, usually expressed in vertical rise of horizontal distance.
See also Pool Profile.
FLOW GRILLE
See Inlet.
FOOT HEAD
A basis for indicating the resistance in a hydraulic system which is equivalent to
the height of a column if water which would cause the same resistance. (100ft of
head is the equivalent of 43 psi). The "total dynamic head" is the sum of all the
resistance in a complete system when in operation. The principle factors of "head"
are vertical distances and resistance due to friction of the flow against the walls of
the pipe or vessel. "Friction head" is the head loss due to friction only.
FREEBOARD
Distance between pool water surface level and surrounding deck level.
FREEFORM
Freely adapted pool-sharp.
FREESTANDING
A pool shell set above ground and self supporting.
GALVANIC ACTION
Creation of an electrical current by electro-chemical action.
GUNITE
Pool shell constructed by spraying concrete mix to form floor and walls.
HALOGEN
A group of elements having closely related properties.
bromine, chlorine and iodine.
This group includes
HANDRAILS
Railing, usually stainless steel, fixed to the pool walls near to the water level for the
purpose of hand hold.
HIGH LIMIT STAT
A temperature operated switch for turning off heaters at a specific high
temperature with manual reset.
HOPPER
Deep end water basin with all four sides sloping to the deepest area for diving. See
also Cage of Safety.
HOSE CONNECTOR
The fitting used to connect the hose to the vacuum wall fitting, usually a
combination hose sleeve and nut.
HYDROJET
A fitting which blends air and water, creating a high velocity turbulent mix.
HYDROSTATIC RELIEF VALVE
One way valve into the pool to help relieve external water pressure outside of the
shell.
HYPOCHLORITE
Chlorine compounds used for pool water disinfection. Commercially available
forms are sodium hypochlorite solution, calcium hypochlorite granules and tablets
and lithium hypochlorite granules.
HYPOCHLOROUS ACID
The active form of chlorine which destroys bacteria and reacts with pollutants
most rapidly.
HYPOBROMOUS ACID
The active form of bromine which destroys bacteria and reacts with pollutants
most rapidly.
INFLUENT
The inflow or entering water to a filter or other device.
IN GROUND OR BELOW GROUND POOL
Pool shell inset into the ground.
INLET or FLOW GRILLE
Fitting for return pool water in circulation system.
INLET SPREADERS - POOL INLET
This is a fitting through which filter water flows when entering the pool via the
return line. Three standard types are in common use, these being fixed flow,
variable flow and variable direction. Dependant on the application involved, any
of these fittings or combination of fittings would be used.
LANGELIER INDEX
Index applied to pool water to access whether it has corrosive or scale forming
tendencies. The equation used to calculate the index takes into account the pH,
alkalinity, calcium hardness and temperature of the water.
MAIN OUTLET OR MAIN DRAIN (Sump Outlet)
Fitting at the deepest point of a swimming pool through which the main flow of
water passes out of the recirculating pump.
MANIFOLD PIPING
The piping with all valves and fittings which is used to connect the filter system
together as a unit.
MARBALITE
'Plaster-like' lining of marble granules/white cement mix applied to concrete pools
to finish the interior system.
MICRON
A unit of size where 1 micron = 1 millionth of a metre, or 1 thousandth of a
millimetre also 1 micron approximately = 0.00004 ins.
MILLIGRAMS PER LITRE mg/1
A unit for expressing chemical concentration. In water, milligrams per litre has the
same numerical valve as parts per million (ppm).
MULTIPLE FILTER CONTROL VALVE
A multiport valve with at least four positions for various filter operations, which
combines in one unit the function of two or more single direct-flow valves.
ORIFICE PLATE
A disc, placed in a water flow line, with a concentric, sharp-edged circular opening
in the centre, which creates a differential pressure to measure flow and to operate
feeders and instruments or other hydraulic equipment.
ORTHOTOLODINE (OTO)
A chemical reagent formerly used in pool water test kits for measuring the chlorine
residual. This compound has now been deemed a health risk and must no longer
be used.
OVERFLOW SYSTEM (Draw off)
Method by which surface pool water is collected for removal to the filter system.
OXIDATION
The chemical process whereby a chemical compound reacts with and destroys
organic impurities. Disinfectants such as bromine, chlorine and ozone possess
strong oxidising properties.
OZONE
A tri-atomic form of oxygen with powerful oxidising properties; used as a water
disinfectant and purifying agent.
pH
Degree of acidity or alkalinity of a water measured by a scale of units 0-14, neutral
or balance point being pH7.
PARTS PER MILLION
A unit for expressing chemical concentration. In water, parts per million has the
same numerical valve as milligrams per litre (mg/1).
PASCAL
A very small unit of pressure in the SI systems and equals the force in Newtons per
metre² of area.
PHENOL RED
A chemical reagent used in pool water test kits to measure the pH of the water.
Usually supplied in the form of tablets or solution.
PLANT ROOM
Location housing pool operational equipment.
POOL DEPTH
The vertical distance between the pool floor level and the normal or operating
water level when the pool is in use.
POOL FLOOR
The portion of the pool interior which is
from the horizontal.
POOL HEATER
A device through which pool water is circulated to increase the temperature of the
water. In the direct type, the heat is transferred directly to the pool water
circulating tubes. The indirect type utilises a separate enclosed system which is
directly exposed to heat generator and which heats the pool water by circulating
the steam or hot water around the tubes of a heat exchanger through which the
water circulates. The heat generator is considered part of every heater.
POOL LEVEL
Pool position by location of water surface in relation to the ground around, main
levels are termed above or on-ground, in or below ground, or half in-ground.
POOL PROFILE
The shape of the walls and floor viewed cross-section from shallow to deep end.
See Cage of Safety.
POOL SHELL
The combined wall and floor structure.
POOL WALL
The sides of a pool above the floor which are vertical at the top and coved at the
bottom, or which are inclined to the pool no more than 45
POTABLE WATER
Another name for drinking water.
PRE-COAT
The pre-coat or initial coating of filter aid on the septum of a diatomaceous earth
filter.
PRE-COAT FEEDER
A device used to feed a calculated amount of filter aid at the start of a
diatomaceous earth filter cycle - following the cleaning operation.
PRESSURE DIFFERENTIAL
The difference in pressure between two parts of a hydraulic system. (Influent and
effluent of a filter, suction and discharge of a pump, the up and down-stream sides
of a venturi or orifice).
PRESSURE UNITS
All units of pressure in modern technology are given in SI units (System
International) as Pascals or Bars. The pascal is such a small pressure that in
practical application the bar is used, where one bar = one hundred thousand
pascals. Also 1 bar = 14.5 pounds/in² (psi) = 29.5 inches of mercury = 33.5 ft of
water. For practical purposes, it can be said that 1 bar = 15 psi = 34 ft of water.
PUMP STRAINER
A device placed on the suction side of a pump, which contains a removable
strainer basket designed to trap debris in the water flow with a minium of flow
restrictions. (Sometimes referred to as a "Hair and Lint Trap").
PURIFICATION
The process of cleaning water by filtration and chemical treatment.
QUATERNARY AMMONIUM COMPOUNDS (QAC)
Chemical compounds or formulations which should not be used as algicide and
cleaners.
RATE OF FLOW
The measurement of the volume of flow per unit of time, usually expressed in
volume per minute or per hour.
RATE OF FLOW INDICATOR
A device to indicate the rate of flow in a pipe line. Sometimes referred to as a rateof-flow meter.
RECIRCULATING
The entire system including the suction piping, pump, strainer, filter, face piping
and return piping.
REDOX POTENTIAL
An electronic measurement which indicates the oxidising power or potential of a
chemical compound. Redox controllers are sometimes used in automatic pool
treatment systems using chlorine or other oxidising disinfectants.
RETURN INLET or FLOW GRILLE
Pool water circulation system fitting. See also Inlet.
RETURN PIPING
The part of the pool piping between the filter and the pool through which passes
the filtered water.
SACRIFICIAL ANODES
Cast ingots of metal, usually an alloy of magnesium, zinc and aluminium bolted
with electrical connection to the walls of the filter. The water reacts with these,
rather than with the filter walls, which are usually made from low carbon steel.
This reduces the rate of corrosion of the steel.
SAFETY ROPE ANCHORS
Anchors set into the pool walls to take safety ropes at pre-determined points. See
also Cup Anchors.
SALINITY
The total salt content of the water.
SCALING
Hard deposits which can block pool pipework and form on pool water surfaces.
Caused by the precipitation of calcium and magnesium carbonate from hard
water.
SCREED
Surface preparation render.
SCUM CHANNEL FITTING (or scum channel drain)
A drainage fitting used in scum channels.
SERVICE FACTOR
A factor indicating the degree to which an electric meter can be operated over a
specified horsepower without danger of overload failure.
SHOCK DOSING
A term usually applied to the process of adding a higher than normal dose of
disinfectant to pool water to water to control algae growth or destroy impurities.
SILVER PROTEIN
A solution containers silver ions, used as a germicide.
SKIMMER-FILTER
A recirculating skimmer with a filter forming an integral part of the device.
SKIMMER WEIR
An overflow device across which the pool surface water flows into the circulating
system, usually self-adjusting for water level changes.
SLURRY FEEDER
A device to feed a variable amount of filter aid during the filter cycle.
SPARGE PIPE
A pipe which is perforated with many holes or slits, to allow water to spread
uniformly over a surface, or to collect it from that surface.
SPRING BOARD
A board designed to produce spring action diving.
STABILISER
A chemical compound, usually cyanuric acid, applied to pool water to stabilise the
chlorine residual against destruction by sunlight.
SUCTION PIPING
That part of the pool piping between the pool and the suction side of the pump,
usually consisting of the main suction, vacuum cleaner suction, the skimmer
suction and/or overflow gutter suction.
SUMP OUTLET
See Main Drain
SUPERCHLORINATION
Process of dosing pool water to a higher than normal level of chlorine to control
algae and destroy organic and nitrogenous impurities.
SURFACE WATER SKIMMER
A device designed to continuously remove surface film and water and return it
through the filter as part of the recirculating system, usually incorporating a selfadjusting weir, a collection tank and a means to prevent air lock of the pump. Each
skimmer deals with approximately 37m² - 75m² (400 to 800 sq ft) of water surface
area, the water passing into the circulating system through the independent coarse
strainers prior to being filtered.
SWIMMING AREA
That area of the pool in excess of 1m (3.3ft) in depth which is devoted to
swimming.
TEST REAGENT
A chemical or mixture of chemicals which, when added to a sample of water
produces an observable reaction. Measurement of this reaction determines a
desired parameter of the sample.
TOTAL DISSOLVED SOLIDS
Are defined as the amount of all materials dissolved in water which would become
solids if the water completely evaporated.
TRANSITION POINT
The point where the floor slope changes from shallow to deep area and bathers
must swim to remain above water.
TURNOVER RATE
The period of time, usually measured in hours, required to circulate a volume of
water equal to the pool capacity.
UNDERDRAIN
The distribution system at the bottom of the filter which collects the water
uniformly during the filter cycle, and which distributes the backwash water
uniformly during the cleaning operation. Normally applies to sand filters.
UNDERWATER LIGHT
A light designed to illuminate a pool from beneath the water surface.
UDERWATER SWEEPER
Suction water sweeper for pool cleaning.
VACUUM FILTERS
Filter tanks working on a vacuum rather than pressure principles, where a pre-coat
is used as the filter medium.
VACUUM WALL FITTING
The fitting in the wall of the pool which is used as a convenient outlet for
connecting the underwater suction cleaning equipment or a recirculating skimmer,
and piping to the pump suction.
VELOCITY
The measurement of motion of air and liquids expressed in metres per second (or
feet per second).
VENTURI TUBE
A tube, having a constricted throat, which causes differences in pressure and can
be used to operate feeding devices, instruments and to measure flow.
WADING AREA
That area of the pool less than 1m (3.3ft) in depth devoted to activity of nonswimmers.
WALL SLOPE
The inclination from vertical in a pool wall, expressed in degrees or in linear
measurements of horizontal distance in a given depth.
WATER DISPLACEMENT
The volume of water displaced by each bather entering the spa.
displacement is approximately 0.06 m³ (13 gallons) per bather.
The water
WATER TESTING EQUIPMENT
An apparatus for measuring and determining levels of chemicals in a body of
water.
WET NICHE
A watertight and water cooled unit submerged and placed in a niche in the pool
wall.
DRY NICHE
A normal weatherproof fixture placed in an opening behind the pool wall which
illuminates the pool through a watertight window in the pool wall.
WINTERISING
Preparing or 'mothballing' the pool and equipment as protection against winter
weather.