How to shock your hot tub or spa

Clean Hot Tub in GardenShock dosing your hot tub water is a term usually applied to the process of adding a higher than normal dose of oxidiser chemical to the hot tub water, this process can also be called oxidising. We advise customers to shock dose their water once a week to control bacteria growth and destroy bather impurities. There are two possible products which you can use to do this; chlorine shock and non-chlorine shock.

Why shock my hot tub?

The main reason anyone shocks their hot tub is to clean the water, but it also helps to clear cloudy water. Other reasons to shock your hot tub include:

  1. To kill bacteria – Chlorine based shock treatments are designed to sanitise the hot tub water and ensure it is safe for bathers.
  2. Remove organic contaminants – Shocking helps to remove organic compounds which are added to the water by bathers. When multiple bathers use your hot tub, organic contaminants can increase to higher levels than standard sanitisers can manage.
  3. Reactivate sanitisers - Your sanitiser (bromine or chlorine) becomes ‘used’ as it attaches to various contaminants, a shock treatment breaks the bonds so that the contaminants are caught in the filtration system and activates free chlorine to continue killing bacteria.

Which Type of Shock Should I use?

Both types of shock treatment have their own benefits and weaknesses. We would recommend a combination of the two, however, this can be different depending on your water type or regular bathing routine.

Chlorine Shock

Due to the fact that this shock treatment contains chlorine, we would only recommend using it after very heavy use, or after a fresh water change to bring the chlorine level higher.

When using a chlorine shock, it is important to recognise that it will raise your chlorine levels and therefore you may have to wait for these to naturally reduce before using the hot tub. You must leave your cover off for at least 20 minutes and run a regular jet cycle to let your hot tub aerate. This will help to prevent chemical damage on the cover and pillows of your hot tub.

You can still use a chlorine shock even if you use a bromine sanitiser, however, you should never mix chemicals dry. Add the chlorine shock after a water change or heavy use and wait for the chlorine level to reduce before adding your bromine.


Non-Chlorine Shock

A non-chlorine shock does not disinfect the water which is why its main use is as a weekly treatment to oxidise the water and help remove contaminants and clear cloudy water. The non-chlorine shock will help your chlorine work better by creating ‘Free chlorine’ which is the type of chlorine needed to kill bacteria. This product will also help those on bromine to activate the bromine and help it work more effectively.

How should I shock my hot tub?

You can easily shock dose your hot tub once you know the hot tubs litrage. Here is an easy step by step:

  1. Remove the hot tub cover so oxygen can get to the water.
  2. Ensure your pH is correct. Between 7.2 and 7.6 if you use a chlorine sanitiser and between 7.0 and 7.4 if you use a bromine sanitiser.
  3. Turn on the circulation to the water is moving. (If you have a blower do not turn this on as it will agitate the water excessively).
  4. Measure 17g of non-chlorine shock per 1500 litres or 35g of chlorine shock per 1500 litres (consult the label instructions as this can vary based on chemical quality and brand).
  5. Carefully add the required shock to the hot tub.
  6. Leave the cover off for approximately 20 minutes.

How long do I need to wait after shocking my hot tub?

There isn't a set period you need to wait before using your hot tub after a shock treatment, however, it is essential to test the water to ensure the chlorine levels are safe. Recommendations vary with ranges between 20 minutes and 24 hours.

When using a non-chlorine shock treatment the product does not sanitise, therefore you can generally use your hot tub 20 minutes after adding it to the water.

Hot tub chemical safety

Below are some important tips when using hot tub chemicals:

  • Always read the label of any hot tub chemical before use and follow the instructions carefully
  • Never mix hot tub chemicals unless instructed to do so by a hot tub specialist
  • Always add chemicals to water, never the other way around
  • Never add chemicals to your Hot Tub water while it is in use
  • Only use Hot Tub chemicals in well-ventilated areas
  • Beware of strong winds when using powdered chemicals
  • Keep all hot tub chemicals out of reach of children and animals at all times
  • Make sure you wash your hands after using hot tub chemicals
  • Outdoor Living Online strongly advises wearing protective clothing whenever handling chemicals
  • Test your hot tub water on a daily basis (we recommend either bromine or chlorine test strips depending on your preferred sanitisation method)
  • Store hot tub chemicals away from heat and moisture
  • Always leave your hot tub switched on (unless changing filters or changing the water in your hot tub)
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