How Often Should You Change Hot Tub Water?

  • By: John Parker
  • Last Updated: November 20, 2022

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 new hot tub, one of the first questions many people ask is “How often should you change hot tub water?” because it seems that many people seem to think you need to empty and refill it every time you use it, just like taking a bath, which is completely wrong.

As a general rule, most manufacturers recommend that you change your hot tub water regularly, perhaps every 3 months.

This does depend on how well you maintain the water quality, 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 rest of this article will help you to decide how often you need to change your 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 you can actually see that you have dirty hot tub water. If the water in your hot tub actually looks dirty or smells bad then 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’s water:

Frequency calculation

Some hot tub owners 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 (known as bather load) 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, then 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 calculation as there are many other factors that influence when I change the hot tub water.

I tend to change mine less frequently than every three months since I am normally the only person to use it regularly. I will sometimes leave it for up to six months even up to a year provided I have none of the other factors above that makes me change it.

Foam

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.

Read my article Why do hot tubs foam

Cloudy water

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

Read my article Why is my hot tub cloudy

Problems with balancing chemicals

If you are struggling to keep your water chemistry balanced to maintain the water quality, there comes a time to just give up.

For example, if you use test strips that show you need to add something to change the levels and that then simply puts something else out of balance. In this case, I would suggest that you simply not continue chasing your tail and empty and refill with clean water.

Smell

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

Urine

Perhaps some wouldn’t believe it but sometimes people do actually pee in a hot tub, particularly children. The hot tub water gets the blood pumping quicker so urine is also produced more quickly than normal. Perhaps it is then tempting to pee where they are rather than getting out, getting 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 change water in hot tub

How to drain a hot tub

There are a number of ways to drain your hot tub, all of which I have used at some time in the past 20 years that I have owned hot tubs.

Briefly, your options are:

  • Drain it using a garden hose to siphon out the water
  • Use a submersible pump
  • Use the drain plug on the hot tub
  • If you have a swimming pool close to the hot tub then you can use the vacuum pipe and the pool pump

For a full explanation and step-by-step guide then please read my article How to drain a hot tub

Hot Tub Maintenance Course

I bought Swim University’s Hot Tub Maintenance Course a while 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 as I have saved by not needing to use as many chemicals as I did previously.

EXCLUSIVE OFFER to visitors of this site
Use the discount code EASY10 at checkout to save 10% on this Swim University course.

How Often Should You Change Hot Tub Water? 1
partial water change hot tub

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 advantages are not only does it 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 the hot tub water won’t freeze when the water is at its usual temperature because the tub’s thermostat would turn on the heater when the temperature starts to drop.

But when you empty it and refill it with the hose, the water temperature will be very low so there is then 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.

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