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The most common sanitiser used in swimming pools is chlorine. But why do we need a sanitiser? Well, a swimming pool is a pretty good environment for horrible bacteria to live in, as well as for algae to grow turning your pool green and unsightly. Chlorine is very effective at killing bacteria and algae to ensure your pool stays safe and sparkling.

It is also a strong oxidiser, so it helps ‘burn out’ debris that gets blown into your pool or material brought in by swimmers. Chlorine levels need to be maintained between 2 and 3 PPM for an outdoor pool. We have already seen how important the pH level is for chlorine to work properly, but the other factor that affects chlorine effectiveness is sunlight. Sunlight can destroy up to 30% of your pool’s chlorine every hour! That’s pretty disastrous, but there is a chemical that drastically cuts down chlorine loss due to sunlight. It’s called Filtrite Sunscreen. Sunscreen effectively ‘blocks’ UV light from destroying the chlorine, and ensures adequate chlorine levels are maintained throughout the day, protecting you and your family from harmful bacteria. You can add sunscreen 2 ways to your pool; either by adding it directly to the water, or by using a pre-mixed chlorine and sunscreen product.

These are called stabilised chlorines. When we add chlorine to water, we get 2 chemicals produced. Let’s call one the ‘killing power’ and the other a relatively inert chemical that doesn’t do much at all in the pool. The killing power is the good guy; he’s the one that goes out to kill bacteria and algae and makes the pool safe.

Remember our pH lesson? The higher the pH, the more of the inert chemical is produced and less killing power!However, ammonia in the water combines with the inert chemical, and forms a new chemical called a chloramine.

This is bad news! Chloramines give off an obnoxious smell as if there is way too much chlorine in the water. They also cause sore eyes. How does ammonia get into the pool?

Well, mainly from bathers! Both sweat and urine contain ammonia! More reason not to pee in the pool! The most effective way to remove chloramines from the wateris to use a non-chlorine based oxidiser. Not only is it the most effective, but you can swim in the pool one hour after dosing. A non-chlorine based oxidiser used regularly will provide you with a clean, sparkling and healthy pool.

There are a number of different types of chlorine products available, so let’s take a look at them.

Non Stabilised Chlorines

These are chlorines that have no added sunscreen so must be used in conjunction with Filtrite Sunscreen.

Calcium Hypochlorite

This is sometimes referred to as granular chlorine. It is calcium based chlorine with strengths varying from 65% to 70%. It must be dissolved in a bucket before adding it to the water otherwise it will bleach your pool liner. Because it contains calcium, it will have an effect on water balance over the long term. It needs to be added daily.

Liquid Chlorine

Liquid chlorine is generally purchased in 15 litre, returnable drums. It has quite a low chlorine level, and also a short shelf life of 6 weeks or so. It is easy to use, because you just have to pour the liquid straight into the pool. However, it is also heavy, awkward and very easy to bleach your clothes!

There are better ways to maintain your pool! It needs to be added daily.

Stabilised Chlorines


Dichlor is fast dissolving granular chlorine that has sunscreen built in with it. Because it is sodium based, it also has minimal impact on water balance. It needs to be added either daily, or every second day, and must be premixed in a bucket of water. It also has the least impact on pH than any other chlorine.


Trichlor is available as either a large tablet, small tablets or granules. It has sunscreen built in so this doesn’t need to be added separately. You can add it using either a floating tablet dispenser or an in-line feeder which is the most convenient. The large tablets are the most common form of Trichlor.

So which one is best for you? Well, your local Clark Rubber store can advise you on which is the most suitable sanitiser depending on your type of pool and bather load. Don’t worry, we’ll sort it out for you.


No one knows pools like Clark Rubber. And that's why we've produced these web pages to show you how easy pools are to look after and to make sure they are always safe and sparkling!