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Pool Chemicals. Adding chemicals to your swimming pool

Adding chemicals to your swimming pool

Swimming pool maintenance is about more than just turning on the filter. It’s a time consuming process involving the checking and adjustment of chemicals, sometimes on a daily basis. Swimming pools are breeding grounds for bacteria, the main cause being the actual swimmers. Other causes are untreated water from rain, or topping up, as well as any debris such as leaves. Bacteria can cause illnesses ranging from ear, nose and throat infections to serious diseases like meningitis. The most common way of protecting pools from bacteria is chlorine.

Water Balance

For pools or spas it is important that the water is tested regularly to determine pH, alkalinity and calcium levels. Your local pool shop will be able to assist you in determining the correct levels of chemicals that are needed and sell you a testing kit so you can check them


The pH is a scale measuring acidity and alkalinity. 0 is the strongest acid, 14 is the strongest alkali, and 7 is pH neutral. A swimming pool needs to be very slightly alkaline, having a pH between 7.2 and 7.8. Chlorine works best at this level, and it’s also around the pH level of human skin, resulting in the greatest comfort level. The swimming pool equipment will also be damaged if the pH is too unbalanced.

To adjust pH, you need to add an acid, like muriatic (hydrochloric) acid, or an alkali, like baking soda (sodium bicarbonate) or soda ash (sodium carbonate). This can be bought as pH+ (plus) or pH- (minus)


There are four ways to administer chlorine; granular, tablet, liquid, and via a salt chlorinator. Each method gives the same result; all you need to do is pick a method in line with your budget and lifestyle. Chlorine kills bacteria by oxidising (essentially ‘burning’) them. You need to maintain a level of chlorine in your pool to kill any new bacteria. It’s best done in the evening and stay out of the pool overnight.

Always use care when opening a container of chlorine. Breathing in chlorine gas can knock you right out, and could be fatal. If chlorine touches your skin, you should wash it off to prevent irritation. If chlorine splashes in the eye, irrigate with water and contact a physician straight away.

Types of chlorine

Granular Chlorine The cheapest type chlorine but it needs to be added manually. The granules aren’t 100 per cent reactive, so they will also result in some waste material. The cheaper the chlorine, the more the residue.

Chlorine Tablets

Slow-dissolving in cool water and can be dispensed automatically via a floating unit or erosion feeder (so called because it passes water from the filter over the tablet to erode it away).

Liquid Chlorine

Is corrosive (pH of around 13.0) and should be handled with care. However, it’s totally soluble, can be automatically dispensed via an electronic system or a salt chlorinator and is ideal for superchlorination.

Salt Chlorinators

The most popular way of administering chlorine. It’s a machine connected to the filter piping that uses salt and electricity to react with the pool water to create chlorine. Some chlorinators have timers for automatic filtering and chlorination, and some have automatic cell cleaners. The unit must be cleaned regularly, and the salt has to be replaced about 100 kg for a 50,000L pool every year.