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How Sunlight Can Affect the Chlorine in Your Swimming Pool

How Sunlight Can Affect the Chlorine in Your Swimming Pool

Balancing water chemistry levels has to be one of the more tedious tasks of pool ownership. External factors such as sunlight can affect the chlorines ability to sanitise the water, but how? Here we’ll explain everything you need to know about the effects sunlight has on the chlorine in your pool and how to avoid disrupting the quality of your water.

About chlorine

Why do we have to add chlorine to our swimming pools?

Chlorine is a powerful sanitising agent that is added to pools to effectively kill pathogens such as bacteria, E. coli, viruses, and salmonella.

What should my chlorine levels be?

Healthy levels of chlorine for a swimming pool are between 1ppm and 3ppm. You should always follow the recommended dose outlined in your user manual to be certain. It is best to refer to this for guidance to prevent premature wear to your equipment and pool.

How often should I add chlorine to my pool?

Ideally, chlorine should be added to your swimming pool twice a week and more so in the summertime or when it is getting a lot of use. You may need to shock the pool to ensure it doesn’t turn green or cloudy.

Not all chlorine is equal

Many assume if they dump a tonne of chlorine in the pool, it will clear it up, but this isn’t always the case. See, the chlorine you are adding to your swimming pool can kill harmful microorganisms in the water but it can only do this successfully when it doesn’t mix with excessive amounts of contaminants. This is good chlorine and is called free chlorine. When it comes into contact with things such as body oils, organic matter or sweat it attaches to it and becomes ineffective. This creates combined chlorine. When your swimming pool has too much combined chlorine, it’s likely the water quality will be compromised if it is not seen too quickly. This is the bad chlorine. Total chlorine is the total of free chlorine and combined chlorine together.

How does the sun affect the free chlorine in your pool?

So free chlorine is the chlorine you want in your pool, but sunlight can affect its ability to work. The chlorine breaks down and is released into the atmosphere when the sun’s UV rays hit it. On a day with full sun, it only takes around 2 hours for 90% of your pool’s chlorine to be broken down.

How to stop the sun from breaking down your pool's chlorine

There are a couple of ways you can prevent the sun from breaking down your free chlorine, here are some of them:

1. Add a stabiliser

A stabiliser (cyanuric acid) essentially protects your chlorine from the sun. It works by binding to the chlorine which makes it more stable when exposed to UV radiation. This slows the rate that your chlorine breaks down and makes it more effective for longer. It can extend the chlorines longevity by 8 times. Using a stabiliser is non-negotiable if you want your pool to stay clean. Pool stabiliser can be bought in either granular form, liquid or pre-added to chlorine. How much stabiliser do you need? Well, this depends on a few factors such as the size of your pool and the type of pool you have. It’s best to follow dosage recommendations listed on your user manual or speak to a professional for advice.

2. Use a pool cover

Using a pool cover is a good idea for many reasons, one of them being that it prevents the suns UV rays from getting to the chlorine and breaking it down. This ensures that your chlorine is protected from the sun, and it can save you a lot of money from not having to top up the chlorine continuously to ensure it doesn’t go green. Using a pool cover is recommended especially in winter when you may not be using your pool as much. It can reduce your maintenance and chemical costs substantially.

3. Add extra chlorine on warm days

When the sun is bearing down on a swimming pool, it will inevitably warm the water up and this can have a negative effect on your free chlorine. Bacteria love a warm environment and will happily multiply at a rapid rate under such conditions. This will turn your free chlorine into combined chlorine, and you’ll need to add double the amount of chlorine to prevent it from becoming unsanitary.

4. Test your water often

Monitoring your pools chemistry levels regularly can give you an indication of where your chlorine levels are at, and it allows you to make adjustments as necessary. Not doing this may see the combined chlorine take over, and your pool becomes dirty rather quickly.

5. Consider an indoor installation

Obviously, this is a drastic measure and not one everyone can accommodate but by installing a pool inside, you eliminate the risk of sunlight breaking down your chlorine levels. There are also other benefits such as no sunburn or leaf litter falling into your pool. Alternatively, you could install a pergola or similar over the pool to block out the sun. Even partial shade protection is going to reduce the rate that the chlorine degenerates. Installing your pool in full shade is another option although, you may find that the pool gets cold when the weather starts to cool down.

6. The colour of your pool may influence the rate the sun breaks down chlorine

Darker coloured pools may absorb more heat, and the water temperature might be higher than that of a lighter coloured pool which can speed up the rate that sun’s UV rays break down the chlorine. However, as darker coloured pools absorb more heat, it can help to extend your swimming season. When choosing a colour for your pool, it pays to weigh up the pros and cons of each before making your decision. By purchasing a cover and using it often, you don’t need to worry about what colour your pool is.

7. A little effort goes a long way

By placing some of the strategies we’ve outlined in place, you can minimise the effect that the sun has on your pool water. A little effort now and then ensures that your pool is crystal-clear and ready to jump in whenever you like. While balancing your pool chemistry levels may seem like an overwhelming task to begin with, once you get your head around it, it is quite simple. You can make it much easier by purchasing a water testing kit, they can provide you with an on-the-spot indication of what needs fixing and what doesn’t. If you own a fibreglass pool, they require very little upkeep and maintenance can be managed with ease. If all else fails or for your convenience, you can hire a professional pool cleaner to take care of it for you.

If you’d like more information on this topic or you are considering a swimming pool or spa for your place, get in contact with our friendly team here at The Fibreglass Pool Company, we have an expansive collection of award-winning pools, and there is an option for every budget and swimming need.

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