When and How Often to Change Hot Tub Water

Hot tub water should be balanced to keep it clean, but it should also be changed regularly for hygiene purposes. But how often should you change the hot tub water?

Generally, the water in the hot tub should be changed every 3 days or at least once every month. But this also depends on how many people use the hot tub. The hot tub water changing formula can give a precise result.

In this post, you will learn when to change your hot tub water. Additionally, I will give you some tips on how to keep the water longer clean.

How often should the hot tub water be changed?

Knowing when to change the water in a hot tub can be confusing, especially for those who are new to the world of hot tubs.

Many beginners believe that the circulation system and chemicals will do all the work to clean the hot tub water.

The truth is that to make the water clean and suitable for prolonged usage, you must drain the water, clean the tank, and replace the water. 

Generally, it is recommended that the hot tub water should be totally replaced at least once every three months.

However, some peculiarities come into play when it comes to how often to change the water in your hot tub.

Apart from all these, a simple formula can tell exactly how often you need to change your hot tub water to minimize health risks.

Hot tub water changing formula:

Divide the number of gallons in your hot tub by three, then divide the result by daily users.

For example, if you have a 200-gallon hot tub that is used by two people daily, using the water changing formula;

(200 divided by 3) divided by 2 = 33

This means that you should empty and refill your hot tub once every 33 days.

But, what does the number 3 mean?

It means that you should generally change hot tub water every three days.

However, the number of people using it will affect this time frame.

For instance, if two adults are in the hot tub at night and two children during the day, divide by six instead of four.

The amount of use can make a difference between changing the water every day or every other day.

Now that you know how to calculate when to change your hot tub water, it is vital to have a hot tub water changing formula plan to remember to do it on time.

Signs that you need to change the water in your hot tub

These are some important warning signs to keep an eye out for.

They tell you that the water in your hot tub needs to be changed as soon as possible. 

  • Cloudy Water: The first thing you should do if the water in your hot tub starts to look cloudy is to shock it. If shocking the water in your hot tub doesn’t work, then you will need to replace it right away. 
  • Foam: If foam reappears in your hot tub after using a de-foamer, it’s time to drain the water, clean your hot tub, and refill it with fresh water. 
  • Smelly Water: As soon as you remove the cover from your hot tub and notice that the water smells, drain it and replace it with fresh, clean, odor-free water. 
  • Pee: It may be surprising to learn that peeing in a hot tub is extremely dangerous. This is due to the presence of a molecule called urea in pee. The urea in the pee reacts with the sanitizer in the hot tub water and form chloramine – a dangerous nitrogen chemical. Chloramine might have some unpleasant side effects if it comes into contact with your skin or when you inhale the steam from your hot tub.

How to change your hot tub water

When it’s time to drain and refill the water in your hot tub, follow these steps to keep the water as pure and clean as possible: 

  1. Clean out your hot tub’s plumbing with a line flushing product. 
  2. Turn off the breaker to your hot tub, then drain the water with a hose or a sump pump. 
  3. Legally dispose of your old water according to your city’s regulations.
  4. Wipe off exposed surfaces and clean or change the filter. 
  5. Fill the container with fresh, clean water. 
  6. Turn on your hot tub breaker and heat the water. 
  7. Add and adjust chemicals as required.

Keep in mind that the more frequently you change your hot tub water, the less work you’ll have to do to maintain the water’s chemical balance.

How to keep your hot tub water clean

Now that you know how often you should change the hot tub water, I will give you some advice on keeping your water clean.

  • Use an algaecide to prevent the algae growth: The algaecide can be bought from any pool store. It will help to keep the water clean and clear.
  • Keep the debris out by using a debris remover. This is a long pole with a net on the end for catching debris.
  • Inform users to shower before using the hot tub: The lotions, oils, and hair products that we use can contaminate the water. Skin cells are lost into the hot tub every time someone takes a bath in it. These impurities accumulate over time, clouding the water. Tell users who wish to use your hot tub to wash off before they use it to keep the water clean for longer. 
  • Mandate users to use shower caps in the hot tub: Hot tub users should wear shower caps or other waterproof hair coverings while they use your tub. This will keep hairs and hair products out of the filters, preventing them from becoming clogged. 
  • Check the pH and alkalinity of your hot tub water: It is important to check the pH of your hot tub water. The pH level of the water in your hot tub should be between 7.2 and 7.8. Anything with a pH of more than 7.8 is considered alkaline, which might result into cloudiness in your water. If you’re a light user, check the water in your hot tub once a week, and if you’re a heavy user, check it 2-3 times a week. A high pH or one that is below 7.2 might have severe effects on your skin, in addition to impacting the quality of your water. After you’ve determined the pH of your water, the next step is to add the right chemicals to adjust it.
  • Regularly sanitize your hot tub: The most widely utilized sanitizers for disinfecting your hot tub are chlorine-based sanitizers. Ensure your hot tub is running before adding your sanitizing chemicals. Leave it running for 15 minutes afterward with the spa cover removed. 

What happens if the hot tub water is not changed?

Water has a limit to how many other substances it can hold before becoming supersaturated.

Calcium, for example, is present in your hot tub in the form of a dissolved salt called calcium chloride. This is referred to as calcium hardness or water hardness.

If you don’t change the hot tub water for an extended period, or if you don’t change it at all, the calcium chloride will build up to the point where it can’t be dissolved.

However, because the calcium must go somewhere, you will notice scaling in several places, such as on your hot tub fixtures, in the filter, and even in the water.

Scaling too much will eventually damage surfaces and damage equipment.

Whenever you soak in a hot tub, many contaminants are left behind.

Sweat, body oils, perfume, lotion, makeup, deodorant, and other biological fluids all land up in the water of the hot tub.

Total dissolved solids (TDS) is the term used to describe all of these contaminants. Read more about the total dissolved solids in my blog post.

Conclusion on changing the hot tub water

Because sanitizer can’t do all the work, and if you keep adding it, supersaturation and a significant level of total dissolved solids will eventually prevent the water in your hot tub from mixing with the sanitizer.

So it’s best to replace the water in your hot tub regularly.

However, sanitizers must be balanced with changing of the water, else the use of sanitizers alone does not make the water clean forever.

The longer you go without changing the hot tub water, debris gradually arises until the water is no longer useable.

Have you any questions about the frequency of changing hot tub water?

Ask me @contactswimfool on Twitter or on Facebook. I will help you.

Have fun in your hot tub!

Photo of author
Hi. I'm Max Berg. I've been in the pool industry since 2015 and have always felt drawn to water. I'm the author behind swimfool.com, where I share my years of experience in pool maintenance and give helpful tips on keeping a swimming pool or hot tub clean. My tips reduce the costs of water treatment and protect the environment.

Keep Reading