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Thursday, 19 December 2013 02:38

Good Chemistry

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Good Chemistry

While a swimming pool will be an enjoyable addition to your home, it can also be a breeding ground for harmful bacteria if not sanitised correctly. To ensure your pool is safe to swim in, Stevie Newbegin speaks to the director at Pool Controls, Liz Hollingdale, for her expert advice on pool sanitation.

Pool ownership is seen as a luxury, and it is. From fitness to leisure, relaxation and entertainment, a swimming pool provides a haven to retreat to in the privacy of your own home. However, with this luxury also comes responsibility. Pool owners must ensure their pool is safe and sanitised, and for many, this can be an overwhelming task.

To simplify pool sanitation, Sydney Pool + Outdoor Design magazine speaks with Liz Hollingdale, director at Pool Controls. Pool Controls has been providing innovative solutions for pool water management for more than 30 years, so Hollingdale is well-versed in the importance of proper pool sanitation, the different sanitisers available and maintaining the correct water chemistry.


Before learning how to sanitise your swimming pool, it’s important to understand why it needs to be done. Learning the risks will ensure you create a safe swimming environment, and don’t put any friends or family members at risk.

“It is vital to sanitise a pool so that harmful pathogens are destroyed. Otherwise, serious illness, and even death, can result,” says Hollingdale.

“[Examples of illness include] amoebic meningitis, giardia, cryptosporidiosis and pseudomonas, which often manifest as swimmer’s ear and skin infections.”

According to Hollingdale, bacteria can enter a pool via the air, bird droppings, and most commonly, on the bodies of swimmers. From pets, to debris and sick swimmers, there is a range of contaminants that can make their way into your pool. By properly treating your pool water with a sanitising chemical, you can prevent the growth of harmful bacteria and keep your pool safe.

As well as illness, bacteria also need to be removed to protect your pool from damage.


While a swimming pool will be an enjoyable addition to your home, it can also be a breeding ground for harmful bacteria if not sanitised correctly. To ensure your pool is safe to swim in, Stevie Newbegin speaks to the director at Pool Controls, Liz Hollingdale, for her expert advice on pool sanitation.


“The pool infrastructure itself can be damaged if the chemical balance of a pool is incorrect. For example, if a pool is incorrectly sanitised, algae may grow uncontrollably and may colonise filters. Serious algae problems can be difficult to resolve and can make the pool very unattractive,” says Hollingdale.

So how do sanitisers work? According to Hollingdale, for a sanitiser to be effective, it must be able to kill pathogens quickly and effectively and there must also be a residual effect to protect the pool as it is being used.

“Essentially, molecules of the disinfectant are capable of passing through the cell walls of waterborne bacteria and once inside the bacteria cell, set about oxidising the various enzymes found there, resulting in the death of bacteria,” says Hollingdale.


There are many different sanitation methods marketed and available, but, according to Hollingdale, sanitation methods have to be approved by the Australian Pesticides and Veterinary Medicines Authority (APVMA) in Australia.

“Popular and approved sanitation methods include the use of chlorine, bromine and ozone, or combinations of these,” says Hollingdale.

“Several other alternative sanitation methods are extensively marketed, but not all are approved for use in Australia.”

Chlorine and bromine

The most commonly used chemicals for pool sanitation are chlorine and bromine, as they are both strong oxidising agents and provide a lasting residual, which means they can remain in the water while the pool is in use and will continually protect against bacteria.

“Chlorine is a strong oxidant and it works by chemically ‘burning’ bacteria. It is the most commonly used pool sanitiser in Australia because it is effective, has a proven track record and is not too expensive. The long-term effect of this sanitiser has been studied extensively and the parameters for safe use are well-known,” says Hollingdale.

Chlorine can be added to the pool in granular, liquid or tablet form. Granular chlorine is convenient, easy to store and affordable, but
can’t be dosed automatically. Liquid chlorine can’t be stored for long periods, but can be dosed automatically through an electronically controlled feeder, and tablets can be automatically dispensed in an erosion feeder, where the chlorine will dissolve over time.

Pool Controls has found that, if used correctly, chlorine ensures highly effective swimming pool sanitation and the elimination of potentially lifethreatening pathogens. However, as chlorine is a powerful oxidant, it is essential that it is used correctly.

“People often complain about the chlorine smell in swimming pools. Ironically, what they smell is usually chloramines, which are produced when insufficient chlorine has been added,” says Hollingdale.

If there is insufficient chlorine in your pool, you may need to ‘shock’ your pool water, otherwise known as super chlorination.

“Super chlorination is when chlorine levels are raised to a much higher level than normal.

This makes sure that all bacteria are totally eliminated from the water. The extra chlorine also removes chloramines. These chloramines are the compounds that smell and can cause eye and skin irritations.”

State health authorities measure sanitiser levels as parts per million (ppm), and Hollingdale explains that a safe level for chlorine is between 3ppm and 5ppm. That said, she believes it’s better to measure chlorine by the oxidation reduction potential (ORP).

“Chlorine operates as an oxidant, and this is how it actually destroys the harmful bacteria. So, a preferable way to measure the effective chlorine is by measuring the oxidation reduction potential (ORP) of the water. This is done electronically, giving a reading in millivolts. Generally, an ORP of 650mV will provide effective sanitation, killing bacteria in one to two seconds.”

Similar to chlorine, bromine is also a strong oxidant that works well killing bacteria. “One advantage of bromine is that is does not form chloramines and is generally perceived to smell better. For this reason, it is often used in indoor spas, where ventilation can be an issue. It is usually a bit more expensive than chlorine, which makes its use in large pools less attractive,” says Hollingdale.

Salt chlorinators

Salt chlorinators offer an alternative way to sanitise your pool with chlorine, and have been very popular in Australia for many years.
Hollingdale believes the reason for their popularity is because once set-up correctly, a saltwater system is capable of steadily producing sufficient chlorine to sanitise a domestic pool.

“Pool owners don’t have to hand-dose their pool with chemicals, and for many this represents a very convenient option,” she says.

Hollingdale finds that hand-dosing chlorine is very ‘hit and miss’, and most pool owners aren’t really sure how much granular or liquid chlorine to add or how to test their pool water chemistry.

“There are much more efficient options on the market these days. Chemical feeders can be fully-automated and some are able to analyse the water chemistry and dose the pool with precisely the amount of chlorine needed.”

For this reason, Hollingdale finds that it is advantageous to choose a saltwater chlorinator that monitors the water chemistry and controls the addition of chlorine; otherwise you may have some adverse effects like chlorine build-up in winter or inability to satisfy chlorine demand in summer.

So, how do they work? Hollingdale explains that saltwater chlorinators produce chlorine gas from dissolved salt (sodium chloride), although mineral chloride salt such as magnesium chloride can also be used.

“As the saltwater (containing dissolved chloride ions) passes over an electrolytic cell, chlorine gas is produced. The chlorine gas immediately dissolves in the water, producing a chlorine residual, which sanitises the water.”


Another sanitisation agent that is even more powerful than chlorine is ozone. Ozone is a naturally occurring gas formed by the sun’s
ultraviolet rays interacting with oxygen atoms and molecules. It can also be formed by a large electrical discharge.

Injected into the water via a compressor or venturi system, ozone is highly effective, and starts to work immediately as it hits the water, killing bacteria and oxidising contaminants.

“Ozone is an even more powerful oxidant than chlorine, oxidising bacteria to death,” says Hollingdale.

Despite its effectiveness at killing all pathogens in its path, Hollingdale explains that ozone is also highly toxic to humans and all traces must be removed from the water before anyone returns to the pool. This means that ozone systems require a chlorine residual to ensure ongoing safe levels of sanitation for pool users.

“A chlorine residual should be maintained in the water to ensure there is ongoing bacterial control. The system will require less chlorine to maintain a safe residual than if chlorine was being used as the primary sanitiser. Therefore, a combination of methods may be the best approach – for example ozone with a chlorine residual,” says Hollingdale.


Before deciding on the right sanitiser for you, make sure that you do your research and understand the system you are installing.

Hollingdale advises that pool owners educate themselves and get advice from trustworthy sources such as the APVMA, which is the government agency responsible for ensuring that registered sanitisers meet Australian Standards.

It is also important to understand how your sanitiser will differ if you have an indoor or outdoor pool, or if your pool is heated.

“An outdoor pool will almost always be better ventilated than the best designed indoor pool, meaning that any chloramines present will have less of an impact. However, ultraviolet light from the sun will result in considerable loss of free chlorine, which should be protected with the addition of stabiliser. In outdoor pools, ultraviolet light can destroy unstabilised chlorine and reduce its effectiveness as a sanitiser,” says Hollingdale.

“A stabiliser is isocyanuric acid and it combines with free chlorine to form a more stable molecule that is less susceptible to ultraviolet light. A stabiliser is often described as ‘sunscreen’ for your pool. It greatly prolongs the life of chlorine in the water, meaning that you have to add less chlorine to your pool to achieve and maintain safe levels of sanitisation.

“For people using saltwater chlorinators, this can be vital because they generate chlorine quite slowly (between 15g and 40g an hour). If this chlorine is unstabilised, it may dissipate too quickly to build up a safe residual and the pool water may not be safe to swim in.”


Once you have a sanitation system in place, as well as your chosen filters and pool cleaners, you need to ensure that you monitor your pool water.

Sanitation effectiveness can be reduced when water is not chemically balanced.

“There are a variety of test kits available to check that various aspects of water chemistry are maintained in the correct range,” says

“Balanced water is water where the following aspects of water chemistry are kept in the appropriate ranges. Chlorine 3–5ppm, pH 7.4–7.6, total alkalinity 80–120ppm and stabiliser 50ppm.”

pH is a measure of how acidic or alkaline water is, and things like topping up your pool, rain, or lots of pool use can change the pH level in your pool water. If your pH level is not within the above range, it will inhibit the sanitising effect of chlorine, so both your chlorine and pH levels should be checked once a week, or more regularly if your pool is in high use.

Total alkalinity is a measure of bi-carbonates, carbonates and hydroxides in the water, and it can lead to the erosion of pool surfaces and equipment as well as make pH levels unstable.

Calcium hardness measures the amount of dissolved calcium in the water and can lead to corrosion on pool equipment. Both total alkalinity and calcium hardness can be measured less frequently, and it is advised you do this through a pool shop.

No matter how you choose to sanitise your pool, it’s important to make sure you administer the sanitiser correctly, follow the manufacturer’s guidelines and maintain your sanitation routine to ensure ongoing protection. If you follow these guidelines, you will be left with the ultimate luxury – a private haven to relax in and enjoy.

Read 108722 times Last modified on Thursday, 12 June 2014 23:17