How to Shock a Hot Tub in 5 Easy Steps

Every hot tub has to be cleaned with a shock agent at some point. But when is this necessary, and how do you shock a hot tub correctly?

The hot tub is mostly shocked with chlorine to remove dirty water and bad smells. But other chemicals such as active oxygen or bromine are also suitable for a shock treatment.

In this article, I will explain why, when, how often, and how to perform a hot tub shock.

Why do you need to shock your hot tub?

Anyone who shocks their hot tub does so primarily to clean the water, but it also aids in the clearing of cloudy water. 

There are a variety of other reasons to shock your hot tub, including: 

Killing of bacteria: This is achieved by Chlorine-based shock treatments. The treatment kills off bacteria in the hot tub, thereby making the water safe for bathers.

Remove organic contaminants: Shocking aids remove organic compounds that bathers add to the water. When numerous people use your hot tub simultaneously, organic pollutants can end up building up to levels that regular sanitizers won’t be able to handle. 

Removing bad smells: As your sanitizer (either bromine or chlorine) attaches to various contaminants, it becomes used. A shock treatment removes the contaminants and bad smells.

The best hot tub shock types

  • Chlorine shock: This is the cheapest and most effective hot tub shock. Monitor the level of the sanitizer, and if the hot tub is outside and not protected by any structure like a gazebo, make sure you shock it when it is dark or at night in order to avoid the sun’s rays eating away at the chlorine, too quickly. 
  • Active oxygen: They’re good at oxidizing other contaminants and cleaning up the water, though. This form of shock is best used on a regular basis, such as once a week, to keep the water in good shape while you utilize your hot tub on a regular basis. Because active oxygen is significantly more expensive than chlorine, using it in a hot tub makes more sense. There are no by-products, and the application is gentle on the user – bathing cannot be more pleasant.
  • Lithium Hypochlorite: This type of shock may be found at your local hot tub or pool supply store. However, there is some doubt because since most lithium is now being utilized to create lithium batteries, lithium hypochlorite isn’t as widely available as it formerly was. This also means that the price of the raw material has increased significantly, making the shock (that is, if you can locate one) more expensive than it was previously. 
  • Bromine: This type of disinfectant can also be used for all of the same reasons as chlorine shock. 
  • Biguanide. This is hydrogen peroxide, but not the kind you will find in your medicine cabinet, so don’t think you will be set with a bottle of hydrogen peroxide from a drugstore.
  • Calcium Hypochlorite: It’s also known as cal hypo, and it’s cheap and convenient due to its widespread availability. However, it should not be used to shock your hot tub as it’s more suitable for swimming pools. Cal hypo is simply unstabilized chlorine, which means that it will lose roughly 95% of its potency in your hot tub after just a few hours of use. It also contains calcium, which would quickly develop scale on surfaces and components in a tiny body of water like your hot tub, thereby potentially causing damage. 
  • Di-chlorine: Technically known as sodium dichloro-s-triazinetrione or dichloroisocyanuric acid, di-chlor shock is a much more accessible product. It’s the active ingredient in most hot tub shock products. You can normally add it to the water without dissolving it first, but always read the label for the manufacturer’s instructions. As indicated by the second scientific name, it contains a small amount of cyanuric acid, which signifies that it’s stabilized and will withstand the hot tub’s heat.
  • Shock for saltwater. Your hot tub is sanitized by the salt chlorine generator, which converts salt to chlorine. As a result, the hot tub is constantly disinfected.

If you’re concerned about the chlorine level being too high, you can also use a non-chlorine shock. 

Use non-chlorine shock against minerals.

If you’re using a spa mineral sanitizer, you’re probably aware that you’ll need to add some chlorine to obtain the complete sanitizing effect.

However, because that chlorine level should only be 0.5 ppm, using chlorine shock would almost certainly result in too much chlorine in the hot tub water.

This is not to suggest that chlorine shock isn’t useful.

If your spa is infected with germs or algae, or if the chlorine level is low, chlorine hot tub shock is the solution.

How to shock a hot tub

To address organic impurities and keep the water clear between regular chlorine shocks, you can regularly apply non-chlorine shock.

Once you understand the nature of your hot tub, shocking the water will be very easy.

Here’s a simple step-by-step guide how to shock a hot tub with chlorine: 

  1. Remove the cover from the hot tub to allow oxygen to reach the water. 
  2. Check to see if your pH is correct. If you use a chlorine sanitizer, it should be between 7.2 and 7.6, and if you use a bromine sanitizer, it should be between 7.0 and 7.4. 
  3. Make sure the water is moving by turning on the circulation. (If you have a blower, don’t use it because it will stir the water too much.) 
  4. Make use of 17g non-chlorine shock or 35g for chlorine shock per 1500L (consult the label instructions as this can also vary according to the chemical quality and brand). 
  5. Carefully fill the hot tub with the required shock. Remove the cover and leave it off for around 20 minutes. 

If you shock your hot tub, make sure to test frequently and monitor the chlorine level to ensure it does not fall below 1 ppm, as you want to keep the chlorine level high over 2 ppm.

You can also shock your hot tub with bromine. This is how you do this:

  1. First, turn on your hot tub.
  2. After that, add a high-shock bromine to the water. It is essential that the bromine level is above 3 ppm.
  3. Finally, run the jets for about 1 hour – you need to be careful to not let the bromine sit in the hot tub for too long.
  4. Test the water in the hot tub. The bromine level in the hot tub needs to be between 1.0 to 3.0 parts per million (ppm).
  5. Finish!

The final bromine level is different in some hot tubs with automatic dispensers because they also dispense two or more other chemicals when producing bromine for the hot tub.

Keep in mind: Some people’s skin are allergic to bromine, but this is rare.

It’s worth noting that the type of hot tub shock you employ is determined by the sanitizer you use.

I have already described to you the different hot tub shock types above.

When to shock a hot tub?

So you’re thinking about shocking your hot tub but don’t know when to do it?

We all have those days where work takes over our lives, and before we know what happened, hours can pass by. But there’s actually not much advice on how long a person should leave their spa unshocked because every situation is different!

Timing is everything. It’s no different with the hot tub shock!

But when is the best time to shock your hot tub?

  • If you’re going to be inside, any hour is good.
  • Wait until nightfall or night if you’re outside and not under a structure like a patio cover.

The main thing is that you need to keep your eyes on the weather.

Look up what the barometric pressure for the day will be.

If it’s low, don’t do it until later in the day when it gets higher. This means there is likely more chlorine generated by your hot tub, so you don’t want to shock while the pressure is low.

If the barometric pressure is high, you can do it when the pressure is lower in the day or wait until night when the air gets more humid, and the hot tub generation of chlorine slows down.

Even if you’re using di-chlor, which does contain a chlorine stabilizer (cyanuric acid), it’s better to keep the chlorine from being burned off before it can do its job.

How often to shock a hot tub?

Other than a big swimming pool, you should shock your hot tub once a week. 

If your hot tub is being used a lot, or if you have a lot of people in it at the same time, you might want to increase this to twice a week.

Always test the water before you shock to ensure that the pH is where it should be, and before returning to the spa to ensure that the sanitizer is where it should be as well. 

But, if you regularly make sure that the water in your hot tub is balanced, then of course, you don’t have to shock the water that often. The use of free chlorine is then completely fine.

How long before I can swim after the shock in the hot tub?

You can swim in your hot tub when the shock is over!

Some people wait 24 hours after their treatments, while others think 20 minutes will suffice.

As with any water treatment product, it’s important to test for safe chlorine levels before getting into an enclosed environment like a pool or spa.

But I recommend sticking close around those measurements so you don’t end up contracting anything from germs that might have been lurking beneath these numbers ( sanitizers help kill bacteria ).

Measure the chlorine level, and when it is below 1.5 ppm, you can bathe in the hot tub again.

Conclusion on shocking your hot tub

Shocking your hot tub is the best way to keep it running smoothly and ensure that you, as well as others who enjoy using the hot tub have a safe experience.

It helps your chlorine and non-chlorine sanitizers do their job by removing and eradicating unpleasant molecules and smells.

It can also help you to avoid draining and refilling your tub for a while.

Your hot tub can be shocked once a month, and this will protect your water against unwanted guests.

It’s pretty easy as long as you follow my simple steps above.

Do you have any further questions, how to shock a hot tub?

Contact me at @contactswimfool on Twitter, Facebook, YouTube, or Pinterest – I’ll be happy to help.

Have fun shocking your hot tub!

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Hi. I'm Max Berg. I've been in the pool industry since 2015 and have always felt drawn to water. I'm the author behind swimfool.com, where I share my years of experience in pool maintenance and give helpful tips on keeping a swimming pool or hot tub clean. My tips reduce the costs of water treatment and protect the environment.

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