How Often Should You Change Hot Tub Water?

Hot tubs provide an invaluable benefit to our lives. They can ease physical pain, relieve tension and provide an escape from stress. Before buying a hot tub, one of the first questions many people ask is “How often should you change hot tub water?” and it seems many people seem to think that you need to empty and refill every time, just like a bath, which is completely wrong.

As a general rule, most manufacturers recommend that the water in a hot tub is changed every 3 months. This does depend on how well you maintain the chemical balance, how often it gets used and the number of bathers that use it. The more it is used then the more often the hot tub water should be changed.

Hopefully the following will help you to decide how often to change hot tub water.

How Often Should You Change Hot Tub Water
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When to change your hot tub water?

Ideally you shouldn’t wait until the water in your hot tub actually looks dirty or smells bad as that may mean you have been using it when the water was past its best.

There are a number of different reasons you may need to change your hot tub water:

Frequency calculation

Some people use a rule of thumb calculation to determine how often to change the water. Basically you divide the total gallons your hot tub holds by the average number of people/frequency that use it and then divide the remainder by 3.

So basically if you have a large hot tub that only you, or you and your partner use, the you will need to change the water less frequently than if you have a smaller hot tub that is used regularly by all the family.

Personally I never really take much notice of this as there are many other factors which influence when I change the water. I tend to change mine every three months since I am normally the only person to use it regularly unless there is another factor which makes me change it.


Foam occurs because surfactants (like salt, detergent and other organic compounds) combine with water and air. The “hydrophobic” (not attracted to water) nature of surfactants is what creates this bubbling upon the water’s surface because they reduce the surface tension.

Before you begin removing the foam or cleaning the water altogether, check all the levels of the tub water. Calcium, sanitizer and pH should be in balance and at their proper rates.

If they are in balance then go ahead and add a chemical foam remover such as Pool & Spa Defoamer to see if that takes care of the problem. If not, you’ll have to clean out your tub and change out the water. If your levels are off, switch the water out without using a foam remover.


If your water is cloudy, and you have tried shocking it without any improvement, then I would just cut your loses and empty the hot tub, clean it and refill.

Problems with balancing chemicals

If you are struggling to balance the chemicals in your hot tub, such that you ad something to change the levels and that then simply puts something else out of balance, then I would simply not continue chasing your tail and empty and refill.


Inevitably, at some stage you will lift up the hit tub cover and be met with an unpleasant almost moldy smell. Although, in theory, you can start adding chemicals to counteract this, personally I just change the water as I try to avoid sitting in a chemical soup.


Perhaps some wouldn’t believe it but sometimes people pee in a hot tub, particularly children. The hot water gets the blood pumping quicker so urine is also produced quicker than normal. Perhaps it is then tempting to do rather than getting out, dried and visiting the bathroom.

Whatever the reason, if you suspect this to be the case then change the water. A hot tub has a relatively small volume of water in it (compared to a swimming pool for example) so the concentration may be quite high. When chlorine reacts to the urine it can produce chloramine which can cause breathing problems.

How to drain a hot tub

How to drain a hot tub

There a number of ways to drain a hot tub, all of which I have used at some time or another.

Siphon with a garden hose

You may struggle to do this on a flat site (and definitely if your hot tub is below ground level. When I was in the UK my garden was on a slope away from the house, so I always used this method.

How to drain a hot tub with a garden hose

  • Put one end of a hose into the hot tub (after switching the electricity off to the hot tub).
    • I actually had a small metal weight I used to tie to that end of the hose to keep it down at the bottom of the foot well or you could get someone to hold it at the bottom.
  • Run out the hose to a convenient area of the garden where the water can drain out or into a sewage input/drain. Make sure the end of the hose is below the level of the other end in the tub otherwise the siphon effect will not begin.
  • Suck on the hose to get the water starting to flow.
  • When the level of the water in the tub goes below the seats use a brush or something else convenient to push the water that sits in them into the foot-well so that is also siphoned out.
  • Inevitably not everything gets siphoned out so use a sponge and a bucket to remove the last of the water.

Use a submersible pump

This is quite a good way to remove the water from your hot tub and it is certainly easy.

Obviously if you don’t have a submersible pump then you will need to buy one, but as you will be emptying your hot tub every 3 months then it will be money well spent. They are not too expensive and since it will not be pumping a huge volume of water, unlike emptying a swimming pool, it doesn’t need to be too powerful. A pump similar to the Superior Pump 91250 1/4hp available on Amazon would work perfectly well.

You just need to connect a hose, drop the pump into the hot tub and switch it on. Job done!

Use the hot tub drain plug

Most hot tubs have a drain plug (sometimes called a spigot) which you can utilize to empty it. My current hot tub was originally on the sun terrace of our apartment and was actually plumbed in to the drains so that I could empty it by just opening a valve. When I had it moved to my house there was no suitable drain nearby so I now use my submersible pump or the method shown below.

You will need to find out where is the drain plug on a hot tub. On most tot tubs you will probably need to remove a side panel to find the drain plug and then connect a hose, a pool backwash hose or even plumb it in permanently, depending on your particular situation.

Use your pool’s pump system

This is certainly the best method I know of how to drain a hot tub fast as it empties in less than 5 minutes.

But of course, many would not be able to use this method as you need to have a swimming pool that is close to the hot tub. My hot tub is so a few times I have used the pool’s pump system to empty the hot tub (very quickly) by connecting the vacuum hose, putting the multiport valve to waste and switching on the pump with the other end of the hose in the hot tub.

Refilling a hot tub

How to get water out of the bottom of a hot tub

Whatever method you use to drain a hot tub, inevitably you will be left with about an inch at the bottom. I have tried a few methods to remove this but in the end I always just fall back on a bucket and a large sponge.

You will have to get into the hot tub to do this but with a large sponge (the sort you might wash your car with) you can soak up the water in no time and squeeze it into the bucket.

Can you do a partial water change?

If you have high TDS (total dissolved solids) in your hot tub then doing a quick partial water change with fresh water can make a big difference. Having lower TDS levels makes keeping the hot tub’s water chemistry significantly easier.

The advantage is not only to reduce TDS levels but it also means the hot tub will reach its ideal temperature much quicker so it can be used again sooner. This is particularly useful if the hot tub is outside in a very cold winter (see below).

Can you change hot tub water in winter?

Fortunately, where I live, the temperature in winter never goes lower than 50ºF so freezing is never a problem. If you live in a colder climate, and your hot tub is outdoors, then it can be an issue. Although it won’t freeze when the water is at its usual temperature because the tub’s thermostat would turn on the heater when it starts to drop, when you empty it and refill with the hose, the water temperature will be very low so there is the potential for it to freeze.

There are a few things you can do to ensure that it doesn’t freeze:

  • If you know you are in for a very cold spell then perhaps delay emptying and refilling until it is over
  • Since the temperatures are normally much lower at night, empty and refill in the morning to give the tub’s heater time to bring the water temperature up before nightfall.
  • You could add a few buckets of hot water when refilling to bring the water temperature up quicker.
  • If the hot tub water is not too dirty you could just do a partial empty and refill so that the resulting temperature of the mixed old hot and new cold water is higher to begin with.

Hot Tub Maintenance Course

I bought this course some months after I bought my first hot tub and was struggling with maintaining it. It was money very well spent and it has paid for itself many times over the years.

How Often Should You Change Hot Tub Water? 1