How often should I change the water in my hot tub or spa?
Many people aren’t sure about how often the water needs changing in their spa or hot tub. This article gives you some advice on how often you might need to change the water.
Why do I need to change the water in my hot tub?
A spa or hot tub has a pump that runs the water through a filter and the water is dosed with chemicals and sanitiser just like a swimming pool.
But a swimming pool doesn’t need to be drained and refilled where as, a hot tub does. Why is that?
The first reason is that a hot tub contains a much smaller volume of water than a pool although just as many people might be using it.
The second thing that makes a difference is temperature. A hot tub is kept at a much higher temperature than a swimming pool and that has an affect on what needs to be done to keep the water clean and clear.
The chemicals and filter will either oxidise or remove a lot of the impurities that enter the water along with the bathers – like body oils, perspiration and traces of soap – but not all of them.
At some point the water will start to become foamy, cloudy or even have a noticeable smell.
Ideally, what you want to do is to drain and refill your hot tub before this happens, don’t you?
How do I work out when the hot tub water should be changed?
You can work out when the hot tub water should be changed by using a formula or by testing the water.
You should be testing the spa water regularly and, if you keep the water in balance, then you should not need to change it so often.
Use a TDS (Total Dissolved Solids) test strip, available from your spa shop, and that will give you a good indication as to when the water is ready for a change.
The other way of getting an idea as to when the water is about to need changing is to use a formula.
First of all you need to know how much water is in your spa.
A 2-seater spa will hold about 650 litres.
A hot tub with 4 seats might hold about 1250 litres.
A large spa that can seat 7 or 8 bathers will be somewhere between 1800 and 2300 litres.
The spa manufacturer will obviously be able to tell you the exact volume of your make and model if you don’t already have that information.
The next thing you need to know is the ‘bather load’ of your spa. That is how many people use it and how often.
When you have that information, you can do the sums. The formula is:
Litres of water divided by the average number of people in the spa for a 20 minute session each day divided by 12. That gives you the number of days between each water change.
For a typical family spa that formula should be telling you to drain and refill your hot tub about every three months.
When you decide to drain your hot tub, it’s a good opportunity to give the plumbing and jets a thorough clean too.
A spa with clean plumbing gives you clearer, fresher water and better circulation. Add a flush product – which you can get from your spa dealer – to the water before you drain and run the pumps on high speed for about 20 minutes.
If your spa hasn’t been cleaned for a while this will probably flush a lot of dirt into your water that can be thrown out when you drain.
We hope this article has been of use to you.
There are many more articles on this site that will give you information on almost every aspect of your spa or hot tub.
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