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How to shock a hot tub


If you own a hot tub or you are considering buying one, you might have heard about ‘shocking a hot tub’ and you are not quite sure what it actually means. We’ve put together a guide to offer some advice and guidance about a hot tub shock, so you know exactly what it means as a hot tub owner.


What do you mean by shocking a hot tub?


Shocking your hot tub is just a way of saying you are adding a higher amount than you usually would when putting in oxidiser chemicals to the water. Oxidisers are used with hot tubs and swim spas to help remove any oil and organic matter from the water. It breaks it down and allows for the sanitiser to be much more effective at cleaning the hot tub. If there is always a great amount of bacteria and germs to break through first, the cleaning fluid will have to work much harder to just get to the starting line during the cleaning process.


Why do I need to shock my hot tub?


Shocking your hot tub is important as it is a key factor in helping the water to be as clean and clear as possible. There are some other reasons that you should regularly shock the hot tub water, such as:

It kills bacteria

A chlorine-based shock treatment is the perfect way to sanitise the water in your hot tub. It helps to keep it as safe as possible for bathers. Any bacteria that is present in the water will be wiped out by a chlorine-based spa shock, and this is exactly what you need.

It removes contaminants

Every time you go in the hot tub it is only natural that you leave behind oils from your body, dead skin cells, makeup, suntan lotion etc. This sounds disgusting when you put it like that, but this is why it is so important to have a regular spa shock routine. Standard sanitisers can struggle to break through these organic compounds and contaminants, leaving traces for the next time you use the hot tub, and leaving scum and cloudy water in the process. By shocking the water, you are oxidising it and breaking down the compounds to leave behind clean water.

Removes chloramines and bromamines

Chloramines are left behind when chlorine granules react with the water. This is what you are smelling when you think of that ‘swimming pool smell’ that we have all remembered since childhood. If you use bromine as your sanitiser, this will release bromamines, which don’t smell but can be toxic to breathe in. You need to use these products to clean the hot tub, but you also need to ensure the water is safe to use post-clean.

Reactivate sanitisers

Your choice of sanitiser will become less effective over time, so shocking the hot tub helps to reactivate the sanitiser. The shock treatment breaks the bond that has been created between sanitiser and contaminants and helps to reactivate the chlorine or bromine to kill the bacteria present.


What chemicals should I use to shock a hot tub?


There are two main types of shock treatment that are used for hot tub water:

Chlorine-based shock

This type of treatment oxidises and disinfects your hot tub water, boosting the sanitiser levels of the hot tub. It isn’t advised to use this type of shock treatment regularly, but it is best used when first cleaning your hot tub water, straight after changing the water, or if you have had more people than usual using the hot tub.

Non-chlorine shock

This oxidises the hot tub, creating ‘free chlorine’. It doesn’t contain any disinfectant, so although you might feel like you need to disinfect your hot tub water regularly, a non-chlorine-based shock treatment does help in removing non-bacterial contaminants and helps to maintain a high quality of water.


How often should I shock my hot tub?


Adding non-chlorine shock to your hot tub once a week will certainly help to remove any contaminants such as dead skin cells, makeup, and moisturiser. It will help to remove the danger of cloudy or scummy water and will also help to reactivate the chlorine or bromine to help kill bacteria.


It is best to shock your hot tub water when the hot tub has just been drained and refilled, and after you’ve had a hot tub party, or it has been heavily used in recent days. Never mix chlorine and bromine when dry, but you can do so in the water.


How should I shock my hot tub?


There are some simple steps that you can follow to effectively shock the water in your hot tub and keep things sanitised and clean to use;

  1. Remove the cover on the hot tub and let oxygen reach the surface of the water
  2. Ensure there is a correct pH balance in the water (between 7.2 and 7.6 with chlorine sanitiser or 7.0 and 7.4 with bromine)
  3. Aerate the water by turning on the jets
  4. Make sure you use the correct amount of sanitiser, based on the specific label instructions
  5. Carefully pour into the spa near to the water inlets, so as to allow for even circulation


Do I need to wait long before using my hot tub after a shock?


Although there is no set time that we can recommend that you wait before use post-shock treatment, there is a way that you can tell. Every brand will provide different recommendations from 20-minutes to an entire day, so follow the instructions carefully. You can, though, take a test strip to check chlorine levels, and if they are safe, you’re free to jump in!


Building in regular shock treatment for your hot tub water cleaning and maintenance routine is the best way to ensure that your hot tub is in perfect working order and continuously safe to use. It helps to kill bacteria and prevent the build-up of cloudy, scummy water from constant use.


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