Glossary of Terms


Alkalinity

This is the measure of a pool waters ability to neutralise acids or alkalis, primarily due to the presence of bicarbonates. If swimming pool water has an acceptable Alkalinity level it will allow the water to buffer against sudden changes in pH, which is one of the leading causes of eye irritations in swimming pools.

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Automatic Chemistry Controller

This is a unit that constantly monitors and adjusts the chlorine and pH levels in pool water by the automated dosing of chemicals.

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Backflow Preventer

A back flow preventer is an automatic valve that is normally used on a potable water supply (tap). In a pool situation it is important that one of these valves is fitted on the water supply to the pool plantroom prior to any outlets for makeup water etc. This is because if the town water supply is shut down while there was "say" a hose filling the swimming pool (actually in the water), it would be possible for the pool water to be siphoned back down the hose and into the town water supply pipe work. This is a Building Code requirement.

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Balance Tank

A balance tank is used in pools that do not use skimmer boxes. Its primary use is for the storage of excess water generated from the displacement of swimmers bodies. A pool with a balance tank maintains a constant depth regardless of how many people are in the pool. Once the swimmers exit the pool the extra water that the balance tank has been holding returns to the pool and the balance tank returns to its normal operating level. The balance tank is also fitted with an equalising and control valve and is an ideal place to dose chemicals that are able to be "slug dosed". The circulating pump's suction is also located in the balance tank.

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CAC

This stands for COMBINED AVAILABLE CHLORINE. When Hypochlorous Acid disinfects organic matter in pool water, byproducts called Chloramines are produced. These Chloromines exist in three different forms and are what gives swimming pool water its distinctive smell and taste.

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Calcium Hardness

This is the content of dissolved Calcium in the pool water. There are also other dissolved minerals in pool water such as Magnesium, but Calcium is the mineral that has the greatest affect on pool water.

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Calcium Hypochlorite

Commonly called HTH, this granular chemical is added to water for disinfection. Calcium Hypochlorite has a strength of 65% and is usually mixed with water to form a solution of approximately 2%.

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Comparator

This is an instrument that is used to test chemical levels in a pool by using the human eye to match a coloured test sample against a colour chart to determine solution strength. This form of testing is only as accurate as the testers ability to perceive the colour of the sample and compare it to the colour chart. Usually chlorine and pH tests are carried out in this way.

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Control Valve

A control valve is a valve that is used to control the water through a pipe in any position from fully open to closed.

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Corrosive Water

This is water that is considerably less than saturated. This water will attempt to saturate itself by dissolving everything that it comes into contact with to build up its content.

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Cyanuric Acid

Sometimes referred to as sun block. Chlorine in the form of Hypochlorous Acid is destroyed by Ultra Violet Light from the sun. Because of this Cyanuric Acid is added to OUTDOOR pool water to minimise this reaction otherwise it is very hard to maintain the chlorine level in an outdoor pool on a sunny day. This is very important for New Zealand pool's because of the higher levels of ultra violet light that we are exposed to due to the Ozone Hole in the atmosphere above us.

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Diaphram Dosing Pump

These pumps work on the principle of a mechanically operated diaphram that creates suction as it is moved. These pumps are widely used in pools but suffer from losing their prime especially in low output situations. To maintain their prime they rely on small one way valves that are prone to malfunction, when this occurs the pumping of the liquid solution ceases.

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Disinfection

Disinfection is the process by which organic matter and pathogens are destroyed in pool water using a disinfectant such as chlorine.

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Equalising Valve

This is a valve that connects the balance tank with the main pool tank, usually at the deepest point in the pool wall. If the balance tank level falls too far below its normal operating level this valve opens via a float valve so that the circulating pump's suction does not run dry.

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FAC

This stands for FREE AVAILABLE CHLORINE. When chlorine is added to water Hypochlorous Acid is produced. FAC is the Hypochlorous Acid that is available in the pool water for the purposes of disinfection.

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Heat Pump

A Heat Pump is a heating unit similar in technology to a chiller or refrigeration unit. It extracts the heat from either a water or air source and transfers it through a heat exchanger to the pool water. A heat pump is operated by electricity but it has the advantage over other forms electric of heating that it produces a Coefficient of Performance (COP). By this it means that it is able to produce more kW's of heat than the kW's of electricity needed to operate the system. Depending on the heat source and its temperature this Coefficient of Performance may be as high as 5:1. This makes it a very economical and cost effective way to heat pools, with very affordable and reliable units now being available for home pools. Heat pumps maintain a very consistent temperature through a digital controller that starts to heat the pool at a 0.5C drop in pool temperature from the set point selected. This means that if the set point is set at 28C the heat pump will start to heat the pool when it drops to 27.5C and continue heating it until it reaches 28C. It then shuts down until the pool temperature drops again.

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New Zealand Standard 4441, 2008

This standard relates to the design and construction of commercial swimming pools in New Zealand. It relates to both hydraulic and disinfection design as well as construction techniques etc. A commercial pool in New Zealand is any swimming pool other than residential pools and includes school, motel/hotel, apartment and public pools etc.

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New Zealand Standard 5826, 2010

This standard relates to the operation of both residential and commercial spa and swimming pools in New Zealand. It contains criteria for chemical levels, testing frequencies, microbiological testing and pool operator qualifications etc. NB. Copies of both of the above mentioned New Zealand Standards can be obtained from the Standards Council, Private Bag 2439, Wellington 6020. Telephone (04) 498 5990 or fax (04) 498 5994.

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One Way Valve

This is a valve which is installed to stop water flowing backwards in a pipe when the circulating pump is turned off. An example of a one way valve in a pool situation would be the foot valve on the pump suction line from the balance tank of a pool. This is used so that the pump does not lose its prime when turned off for hair/lint strainer cleaning etc.

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Overflow Channel

This is the channel that runs around the perimeter of a pool fitted with a balance tank. The purpose of this channel is to collect and direct the pool water from surface filtration to the balance tank. A plastic grating normally covers this channel.

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Ozone Generator

Ozone is another pool water disinfectant. Ozone is a very powerful disinfectant that is able to destroy tastes and odours in pool water. Ozone is a gas and is produced by passing a high voltage electric current through oxygen. The resulting Ozone gas is dosed into the pool water where it reacts very quickly. As Ozone is highly toxic any residual of it must be removed by reaction tanks prior to the water entering the pool again. For this reason a residual disinfectant such as chlorine must be used in conjunction with Ozone. It would be "fair to say" that Ozone is becoming less favoured in the pool industry worldwide due to high capital and maintenance costs and often less than expected performance.

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Peristaltic Dosing Pump

This type of pump works on the principle of a cam roller, usually three lobed, rolling around and compressing a flexible dosing tube. These pumps have adjustable dose rates and are usually available with a range of different sized tubes. This means one pump depending on the setting and tube size, can offer a very large range of outputs. These pumps are completely self-priming as opposed to Diaphram Pumps so they are ideally suited to pool use.

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pH

This is the measure of whether pool water is acidic or alkaline. It is very important in pool water chemistry as its level has a significant impact on the ability of chlorine to react with organic matter, especially ammonia. Different pH levels will produce different types of Chloromines.

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Photometer

This is an electronic instrument that passes a light though a coloured test sample and measures the intensity of the light on the other side of the sample container. This result is either directly expressed as a solution strength or the strength is determined by comparing the chart against a calibration chart. This form of testing is very accurate and wide ranges of tests can be performed.

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Saltwater Chlorinator

This is a form of disinfection where salt is added directly to a pool's water to form a very weak salt solution of 5000 to 7000ppm. If dosed correctly the level of salt in the pool should be barely detectable by taste. The pool water is then passed through a cell where a low voltage electric current is passed through it. This is called an electrolytic process and the result is the production of chlorine.

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Scale Forming Water

This is water that is over saturated and can no longer hold minerals in solution. This water will attempt to throw off some of its content by precipitating minerals out of solution in the form of scale.

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Skimmer Box

A skimmer box is either a recessed or wall mounted box that is used to collect the pool water and direct it through the pool's filters etc via the pump and recirculation pipework. The normal swimming pool water level for a skimmer box is approximately half way up the height of the skimmer's throat when no body is in the pool. This is so that when people enter the pool and their displacement increases the water level, the skimmer throat stays open to the surface of the water, so surface filtration can continue.

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Sodium Bicarbonate

Commonly called Baking Soda this chemical is used to increase alkalinity, it also increases pH but to a lesser degree than alkalinity.

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Sodium Bisulphate

This is a chemical that is used to decrease pH.

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Sodium Hypochlorite

Commonly called Liquid Chlorine, this chemical is added to water for disinfection. Ian Coombes Limited supplies Sodium Hypochlorite at a solution strength of not less than 135 grams per litre, this equates to 13.5%.

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Sodium Thiosulphate

This is a chemical that is used to neutralise chlorine. It is especially useful in reducing the chlorine level in an over chlorinated pool to a level that is safe for swimming.

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Solar Heating

Solar Heating is a process where the sun's energy is collected and used to heat a pool. This technology is usually used for home pools, but sometimes used commercially. The draw back of this technology is that the resulting pool temperature is not consistent as heating is only available when the sun is out.

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Surface Filtration

Surface filtration is the removal of debris from the water surface by this water passing into a skimmer box or over a weir and into an overflow channel so it can be recirculated through the filters etc.

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Swimming Pool Surface Area

This is the measure of a pools water surface and is expressed in square metres (m2).

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Swimming Pool Volume

This is the measure of a pools capacity and is expressed in either litres or cubic metres (m3)

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TAC

This stands for TOTAL AVAILABLE CHLORINE. This is the total chlorine concentration that exists in the pool water and is the sum of the FAC and CAC. Therefore TAC minus FAC equals CAC.

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Three Way or Diverting Valve

This is a valve that is used to direct water into different pipes depending on its position. These valve are commonly used to open pool vacuum lines prior to the circulating pump and also for heating control of both pool water and enclosure air.

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Total Water Balance

Balanced water has the proper levels of pH, Alkalinity and Calcium Hardness. It can be further described as water that is neither corrosive nor scale forming. This is derived from the fact that water will dissolve and "hold" minerals until it becomes saturated and cannot hold any more in solution.

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Ultra Violet Disinfection Unit

This unit disinfects pool water as it passes through it by passing a high intensity Ultra Violet Light through the water. Newer Medium Pressure UV Technology as opposed to the older low-pressure technology is rapidly becoming more favourable than Ozone for the destruction of chloramines in pool water. Generally UV has a far lower capital and maintenance costs than Ozone and is producing significant improvements in pool water quality.

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