Posted by Alex Clamp in
Maintaining a Hot Tub Guides
on 16th March 2023
Keeping your hot tub topped up with sanitiser will help keep it clean and hygienic. But it won’t do the job on its own.
Luckily, a simple way to stop contaminants from building up in your home spa is to use hot tub chemicals to shock it.
Here’s everything you need to know about how to shock a hot tub – including a simple step-by-step guide that will give your home spa and hot tub water a hygiene boost in minutes.
Photo © Hot Tubs Hampshire
Hot tub shock is a dose of oxidiser big enough to “shock” your spa’s water. This does four things:
Chlorine-based spa shock will wipe out and kill any bacteria that are calling your hot tub home.
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 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.
Chloramines are left behind when chlorine granules react with the 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.
Using hot tub chemicals to shock your hot tub helps eliminate these nasty byproducts so you can breathe easily during soaks in your home spa.
Over time, your sanitiser becomes less effective. Shocking your hot tub will reactivate the chlorine or bromine in its water, giving it a boost to kill bacteria without having to add more sanitiser.
Photo © Coast Spas
There are two main kinds of hot tub shock: chlorine-based shock treatments and non-chlorine-based. We recommend you stock up on both because they serve different purposes:
Non-chlorine shock oxidises your hot tub to create “free chlorine”, but doesn’t contain any disinfectant.
Many people find they need to disinfect their spa’s water regularly, and while non-chlorine shock won’t help with bacterial issues, it can do wonders for removing other forms of contaminants and keeping the quality up even when used frequently!
Adding non-chlorine shock to your hot tub every week will get rid of any contaminants you don’t want to be sharing your spa with, like skin cells and moisturiser, so consider putting in one weekly maintenance dose as part of your routine hot tub maintenance program.
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 can kill bacteria growth more effectively.
Chlorine-based shock treatments are the perfect combination for both oxidation and disinfection of your tub. It does everything its non-chlorine counterpart does as well as boosting your spa’s sanitiser levels.
Although regular use is discouraged, chlorine-based shocks can help keep your hot tub water clean upon first opening, after a water change, or when you have had an increased number of bathers – just be mindful that excessive usage may cause damage to your tubs plumbing and piping if not carefully monitored.
The best times to reach for a chlorine spa shock are therefore:
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.
Photo © Hot Tub House Yorkshire
You’ll get the best results if you run through this hot tub care routine whenever shocking your hot tub:
First, grab everything you’ll need:
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.
It is also important to keep the circulation pump running during the shock treatment, otherwise risk your hot tub water becoming too stagnant. Also, ensure you have removed your hot tub cover before beginning the shock treatment process.
You don’t want hot tub shock on your skin or in your eyes. So, don’t forget to wear safety gloves and safety goggles before you go any further – and wear long sleeves, trousers, and shoes so you’re covered up. If you accidentally spill any hot tub shock, clean it up immediately.
Now it’s time to grab your hot tub shock. Refer to the manufacturer’s 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.
Carefully add your shock and leave your hot tub’s jets to circulate it for at least twenty minutes. Leave your hot tub uncovered during this time so the chemicals have a chance to off-gas.
Check your hot tub shock 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 around. That way guests won’t be left waiting for the pH levels to drop before they can hop in.
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 heavy bather load 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.
Add spa shock to your hot tub during the day and the sun’s rays could 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.
When it comes to shocking your hot tub, never guess; always measure. Calculate the necessary shock dose based on how many gallons of water are in your hot tub and follow directions printed directly from the product’s label for an accurate dose.
If you’re unsure about capacity levels, simply multiply the length, width, and depth (in feet) together to calculate total volume – then multiply that figure by 7.5 for an estimate of how many gallons it holds!
If you are still struggling, do not hesitate to contact your hot tub manufacturer – they’ll be able to provide all information needed!
The answer is (at least) once a week. If it receives more frequent heavy usage, or if several people are using it at one time, aim for twice weekly as an added precaution to ensure smooth sailing!
Before shocking and re-entering the spa be sure to conduct pH balance tests of your water – which will help determine when a chlorine boost may be needed.
Shock, which is comprised of a higher concentration of chlorine or a non-chlorine alternative, is designed to break down organic contaminants and sanitize the water more effectively than regular chlorine alone.
Chlorine, on the other hand, serves as the daily sanitiser to keep the pool clean and safe by neutralizing bacteria, algae, and other microorganisms.
Therefore, shock can be considered stronger than chlorine due to its increased potency, but it should be noted that a combination of both treatments works best in maintaining pristine hot tub and pool water.
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About the author
I am the Content Writer and Marketing Officer at WhatSpa? Magazine. I have worked at WhatSpa? for over 8 years, and I recently graduated with Distinction from Northumbria University with a Master's degree in Occupational and Organizational Psychology. My role at WhatSpa? is to ensure that all hot tub lovers can easily access the highest quality and most up-to-date content, news and information from within the UK wet leisure industry.
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