Hot tub shock is a dose of oxidiser big enough to “shock” your spa’s water. This does four things:
Chlorine-based spa shock wipes out any bacteria calling your hot tub home.
Removes organic compounds from the water
Every time you use your hot tub you leave the likes of body oils, hair, dead skin cells, suntan lotion, and makeup behind.
This is totally normal. But these organic compounds can lead to nasty problems like hot tub scum and cloudy water if they’re left to linger.
Hot tub shock oxidizes your hot tub’s water, which helps it break down these organic compounds and keep your hot tub squeaky clean.
Removes chloramines and bromamines
Chloramines are left behind when chlorine reacts with water. They’re what gives off that distinctive swimming pool smell.
If your hot tub sanitiser of choice is bromine, that releases bromanines. These don’t smell as strong, but aren’t something you particularly want to be breathing in.
Shocking your hot tub helps eliminate these nasty byproducts so you can breathe easy during soaks in your home spa.
Reactivates your sanitiser
Over time, your sanitiser becomes less effective. Shocking your hot tub will reactivate the chlorine or bromine in its water, giving it a bacteria-killing boost without having to add more sanitiser.
Which spa shock should you use?
There are two main kinds of hot tub shock: chlorine-based shock treatments and non-chlorine-based.
We recommend you stock up both, because they serve different purposes.
Non-chlorine spa shock oxidises your hot tub but doesn’t contain any disinfectant.
Add it to your hot tub every week and it will get rid of any contaminants you don’t want to be sharing your spa with, like skin cells and moisturiser. This will help prevent the water from becoming cloudy or scum from developing.
A non-chlorine shock treatment will also reactivate your chlorine or bromine so it kills bacteria more effectively.
Chlorine-based hot tub shock contains both oxidisers and disinfectants. It does everything its non-chlorine counterpart does as well as boosting your spa’s sanitiser levels.
However, the chemicals in a chlorine shock are quite harsh and can damage your hot tub’s components if overused.
The best times to reach for a chlorine spa shock are therefore:
When you’ve just refilled your hot tub and want to quickly get the sanitiser levels up.
After particularly heavy hot tub use, like after a party where several guests enjoyed a soak.
One thing to note: while you should never mix chlorine and bromine when they’re both dry, chlorine-based shocks are fine to add to your hot tub even if bromine is your sanitiser of choice.
How to shock your hot tub
You’ll get the best results if you run through this routine whenever you shock your hot tub:
First, grab everything you’ll need:
Your hot tub shock and a measuring cup.
Hot tub test strips.
Chemical-resistant gloves and safety goggles.
Then use a test strip to test your hot tub’s pH level. It needs to be between 7.2 and 7.6, so adjust if needed and then test again.
Keep your hot tub running, as this will help mix the shock into your hot tub’s water. You’ll also want to close your hot tub’s air valves so its jets aren’t running too strong, as that would cause the chemicals to dissipate too quickly and your shock to not work properly.
You definitely don’t want hot tub shock on your skin or in your eyes. So, put on your gloves and safety goggles before you go any further – and wear long-sleeves, trousers, and shoes so you’re covered up. If you spill any hot tub shock, clean it up immediately.
Now it’s time to grab your hot tub shock. Refer to the manufacturers’ instructions to see how much you need to add based on the amount of water in your hot tub. Refer to your hot tub’s manual if you’re not sure what your spa’s capacity is.
Precision is key here, so be sure to carefully measure out your shock treatment before adding it to your spa. Never try to eyeball it.
Add your shock and leave your hot tub’s jets to circulate it for at least twenty minutes. Leave your hot tub’s cover off during this time so the chemicals have a chance to off-gas.
How long should you wait to use your hot tub after shocking it?
Check your hot tub shock’s label to find out how long you need to wait until you can hop in your hot tub again. This will usually be between twenty minutes and an hour.
Both chlorine and non-chlorine shocks raise your spa’s pH levels. So, always test your spa’s water again before hopping in, no matter how long you’ve waited. Make sure the pH level has dropped back down to 7.6 before you get in your spa, as it’s not safe to use until then.
If you’re planning on entertaining people in your hot tub, it’s always a good idea to shock it the day before people are coming round. That way guests won’t be left waiting for the pH levels to drop before they can hop in.
How often should you shock your hot tub?
If you use your hot tub most days you should shock it at least once a week. Bump this up to twice a week if your spa gets used multiple times a day or you have a lot of people in it every time it’s used.
And if you go on holiday or just don’t use your hot tub for a few weeks, give it a chlorine shock before you hop back in for the first time to give it a hygiene boost.
When should you shock your hot tub?
Add a chlorine shock to your hot tub during the day and the sun’s rays could actually burn off the chlorine before it has a chance to work properly.
So, always add hot tub shock to your spa at dusk or night to make sure it works as effectively as possible.
Shocking your hot tub every week is an easy way to give it a bacteria-busting and contaminant-killing hygiene boost.
Make it part of your regular hot tub maintenance routine to make sure your sanitiser works as effectively as possible to keep your spa squeaky clean.
Just remember: non-chlorine shock is best for regular use, but reach for the chlorine shock if you’re looking to quickly get your spa’s sanitiser levels up as well as oxidising its water.
And for more hot tub maintenance tips – plus our pick of the best hot tubs on the market today for every budget – pick up your free copy of the latest edition of WhatSpa? magazine.
I am the Editor-in-Chief at WhatSpa? Media Group and my job is to keep you informed about the very latest hot tubs on the UK market... the best job in the world! When I'm not being deluged with press releases and hot tub brochures I enjoy keeping fit and participating in endurance events including triathlons and distance running.