How to lower chlorine in a hot tub: expert tips to keep your levels correct

Find out how to lower chlorine in a hot tub to keep your hot tub water comfortable yet hygienic

A large hot tub on a backyard terrace
(Image credit: Finmiki Images / Getty)

If you need to know how to lower chlorine in a hot tub, you probably have caught a whiff of the distinctive chlorine smell in your hot tub water that's stronger than usual. 

A hot tub is a wonderful, luxurious addition to a backyard, as many of us discovered over the past couple of years. However, hot tubs also do require regular maintenance and the use of chlorine to keep them hygienic. 

Even the best hot tub will quickly become unusable if there is too much chlorine in it. Don't worry, though: lowering chlorine in a hot tub is not difficult and, provided the imbalance isn't huge, won't take long to fix. Follow these expert tips to restore chlorine levels in your tub and make it pleasant to use again. 

hot tub on deck surrounded by bamboo

(Image credit: Future)

How to lower chlorine in a hot tub in 3 easy steps

If you've found that chlorine levels in your hot tub are too high, there are several ways to get them back down again. We've asked Terry Marsh, the owner of Hyperion Hot Tubs (opens in new tab), to summarize the most effective methods.

  1. Wait it out Chlorine levels will drop naturally over time. 'You can speed this process up by opening the cover and allowing sunlight onto the water,' advises Terry. 'The sun's rays will help to break down the chlorine and reduce the levels in your hot tub.' This method is 'great if you have some time to allow this to work and a nice sunny day.' You may also need to remove your hot tub shelter if you have your spa covered by a pop-up gazebo, for example, to allow the sunlight to reach it effectively. 
  2. Drain some water from your hot tub and refill it 'This will dilute the chlorine level in your spa quickly.' The only disadvantage of this method is that 'you will need to wait for your spa to heat back up again. It does so at a rate of around 2˚C an hour.' 
  3. Purchase a chlorine reducer A chlorine reducer, such as sodium thiosulfate (available from Amazon) (opens in new tab), 'will work quickly to reduce levels.' However, 'putting in just a little too much may see you with no chlorine left', says Terry. Some people experience difficulty in achieving a chlorine reading after using sodium thiosulfate, so he advises only using it as a last resort.

A large hot tub in the corner of a backyard

(Image credit: Hyperion Hot Tubs)

What are the correct chlorine levels for a hot tub?

When working out how to lower chlorine in a hot tub, you'll obviously need to know what the correct level to aim for is. You should be looking for a chlorine level in a hot tub of 1 to 3 ppm (parts per million). The good news is that it does not take a lot of chlorine to achieve this level. To be more specific, 'for an average size spa of 1,200 litres, this would only take around 7.5grams to reach the upper limit.' Terry specifies that 'that's only the equivalent of two teaspoons.' 

This amount is still only a general guideline, though. 'You should check the product packaging for an exact amount as it can vary a little between brands.'

To check the chlorine levels in your hot tub, a test kit such as the EASYTEST 7-Way Pool Test Strips from Amazon (opens in new tab), is an inexpensive way to keep on top of your hot tub maintenance

A barrel hot tub in a forest setting

(Image credit: Finmiki Images / Getty)

How long does it take for chlorine levels to go down in a hot tub?

There is no set rule for this, and the answer will depend on several factors, from the initial chlorine levels to the cleanliness of your hot tub. Terry Marsh says that 'it could take anywhere from a couple of hours to a few days, depending on how much the spa was overdosed by and the conditions within the hot tub. A dirty hot tub would use up chlorine far quicker than one that is immaculately clean.'

It goes without saying that knowing how to clean a hot tub and cleaning a hot tub filter correctly are also an essential part of your hot tub care routine. 

Can I go in my hot tub if the chlorine is too high?

It's not a good idea to use your hot tub if the chlorine levels are too high. 'The raised levels could well irritate your skin, eyes, nose, and throat. It's really not worth it,' cautions Terry Marsh. 

While not everyone reacts to chlorine badly and it won't harm your health long-term, you could end up with a rash or very dry skin.

A hot tub in closeup

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How to avoid chlorine levels that are too high for your hot tub

Prevention is the best cure here. So rather than having to find ways to lower chlorine in a hot tub and wait hours or even days to restore the correct chlorine levels, follow these easy tips to keep your chlorine at the right level: 

  1. Test your water before adding chlorine, it may not need any!
  2. Make sure that you read your chemical bottle label and the dosage instructions. Avoid just throwing in a capful and hoping for the best. Instead measure out the amount properly. 
  3. If you use a tablet dispenser, such as the U.S. Pool Supply floating chlorine and bromine chemical dispenser from Amazon (opens in new tab), you should still check your levels and remove the dispenser from the water when the level is correct.

If you do find that the chlorine level in your hot tub is too high, though, don't panic. In a few simple steps, you can get it down again. You may also consider just draining your hot tub and refilling it with fresh water, which is something you should do regularly anyway.  

Anna writes about real estate, interior design, and gardening. Her work has appeared in Homes & Gardens, Livingetc, and many other publications in the US and the UK. Before embarking on her writing career, Anna taught English at university level and is the author of a book called London Writing of the 1930s. She currently splits her time between London and the Midwest US. She is an experienced outdoor and indoor gardener and has a passion for growing roses and Japanese maples in her outside space.