Hot Tub Chemicals Guide

Yay! You own a hot tub or are about to invest in one.

We've created this guide to explain how different chemicals can affect the water of your tub (or swim spa) and how to use and get the most from them. This way you can maintain a clean, healthy and safe environment for you and your bathers to use.

Treated similarly to swimming pools, there are many challenges involved in maintaining the water in your spa. And understanding how and why you use each chemical is a great place to begin. So, without further ado, let's dive in.

Your hot tub’s chemistry in a nutshell 

As your hot tub is a warm environment, its chemical balance is constantly changing. This could be due to changes in outdoor temperatures, rainwater, bodily oils like sweat and even hard water – if you live in a hard water area.

The easy way to keep your water safe and clean is by testing it regularly. Then, just add the right chemicals to keep bacteria at bay. Simple.

Below we’ve listed our most commonly asked questions. Take a look.

Can I use my hot tub without any chemicals?

Simply, no, your tub needs chemicals to keep your water and you and your bathers safe. Above all, your water needs to be clean, so the use of sanitisers will keep bacteria levels down. Without using chemicals, you could be putting yourself and other bathers at risk.

What chemicals do I need for my hot tub? 

Hot tub starter kit
  • Hot Tub Sanitiser – kills any present bacteria in the water
  • PH Increaser – for when your water is too acidic.
  • PH Decreaser – for when your water has high alkaline levels.
  • Alkalinity Increaser – for when your water has low alkalinity.
  • Test Strips – to determine the current chemical levels in your water. It reads sanitiser, pH and Total Alkalinity.
  • No Foam – to ensure pollutants like perfumes or lotions can be easily filtered away.
  • Chlorine-based shock treatments – kills bacteria, removes contaminants and reactivates sanitisers.
  • No Scale – to prevent scaling and calcium from solidifying in your tub in hard water areas.
  • Calcium Hardness Increaser – raises calcium levels in soft water areas.

To make life easy, we offer chemical starter kits with everything you need to set get your hot tub water ready to use. 

What chemicals do I need for my inflatable hot tub? 

Proper chemical maintenance is essential to prolong the life of your inflatable hot tub. Treat its water care the same as you would an acrylic hot tub, and follow the advice above. However, bear in mind that inflatable tubs can be more susceptible to water contamination, due to the smaller volume of water they hold, and less powerful filtration than most hard shells, so keep an eye on your chemical levels. 

What is hot tub sanitiser?

A sanitiser is a chemical which is used to kill bacteria in your spa water.

There are three types of sanitiser 

What is pH?

pH Plus

PH measures acidity and alkalinity in water on a scale numbered from 0-14; a measurement of 7 is considered neutral or balanced.

A level between 7.2-7.8 must be maintained. Below this indicates that your water is too acidic, which isn’t good for bathers as it can cause itchiness and eye burn. Above this means that your water is too alkaline, contributing to scale build-up. We advise that you regularly test your hot tub pH levels.

Using a pH Increaser or Decreaser helps to balance these levels.

What is total alkalinity? 

Total Alkalinity (TA) measures the amount of dissolved alkaline substances in water. Alkalinity helps control pH levels, so it must be balanced correctly. If your water’s TA is too high or low it will affect the natural balance and hardness.

A level between 80-120mg/l ppm must be maintained. Anything above or below this range makes the pH difficult to maintain.

Using Sodium Bicarbonate or an Alkalinity Increaser will help raise alkalinity levels. A pH Decreaser will lower your alkalinity levels.

Find out more in our balancing your hot tub pH levels and total alkalinity guide.

What is total hardness? 

Total Hardness (TH) measures the amount of calcium and magnesium mineral content in the water and determines how problematic it will be. In a state of Total Hardness, you'll notice scaling around the shell and cloudy water.

A reading between 100-250ppm is advised. If your calcium levels are above this, usually in hard water areas, use a scale control product to keep calcium from solidifying on your hot tub's shell and internal parts. However, if your reading is below 100 ppm, we recommend using a Calcium Hardness Increaser to raise the calcium levels.

What is PPM?

When measuring out the dose of any chemical, it’s usually measured in ppm (part per million), which is the same as mg/l (milligrams per litre).

For example, the level of chlorine needed in your hot tub is between 3-5ppm or 3-5mg/l.

What is hot tub shock treatment?

Chlorine shock

Hot tub shock is an oxidising water treatment that quickly raises the level of sanitisation. This should be done weekly as part of your hot tub maintenance, if you’ve not used your hot tub for a while or have used it excessively.

There are four main reasons to shock your tub:

  • It kills bacteria to keep your water safe for bathers.
  • It eliminates organic contaminants after heavy use, plus it treats cloudy water.
  • It reactivates (chlorine) and regenerates (bromine) sanitisers.
  • It creates more ‘free’ chlorine and bromine – as your sanitiser works. Shock treatment sticks to waterborne bacteria until it’s no longer active then transports them to your filter for extraction.

The learn more, read our guide on how to shock your hot tub.

How soon can I use my hot tub after adding chemicals? 

Hot Tub Water Testing

Once you’ve added chemicals to your hot tub, we advise that you wait for at least 20 to 30 minutes before testing the water again. If the levels are balanced, you can take a dip.

If levels are showing as too high or too low, it could take up to 24 hours for the balance to adjust. Be sure to test the water each time and refer to the chemical’s instructions for use.

How long do hot tub chemicals last?

It varies on what type of chemical you’re using and how it’s stored. To prolong the shelf life, chemicals should always be stored away from heat and moisture. If in doubt, refer to the guidelines on the packaging.

How do you dispose of hot tub chemicals? 

Never dump old or unwanted chemicals as they can be very harmful to the environment and local wildlife. Contact your council’s local waste disposal unit or recycle centre for advice on how to dispose of them safely.

Where can I buy all the recommended chemicals for my hot tub? 

Always buy your chemicals from a reputable retailer and ensure your chemicals are specifically designed to be used in hot tubs or spas. Using incorrect products may damage your tub or harm your bathers.

We stock hot tub chemicals for all makes and models of hot tubs including:

  • Outdoor Living
  • Jacuzzi
  • O-Care
  • Blue Horizons
  • AquaChek
  • AquaFinesse
  • AquaSparkle
  • Spa Frog
  • LaMotte
  • Lovibond
  • Swirl Away

Hot tub chemical safety

Here are some important tips on how to use your chemicals safely:

  • Always read the label and ensure you follow its instructions.
  • Never mix hot tub chemicals unless instructed to do so by a specialist.
  • Always pre-dissolve granules in a container before adding them to your tub, this ensures an even distribution.
  • Always add chemicals to your spa and not the other way around.
  • Never add chemicals to your hot tub while it’s in use.
  • Only use hot tub chemicals in well-ventilated areas.
  • Beware of strong winds when using powdered chemicals.
  • Always store hot tub chemicals out of reach of children and animals.
  • Wash your hands after use.
  • We strongly advise that you wear protective clothing when you handling hot tub chemicals.
  • Test your hot tub water daily with test strips to monitor chemical levels.
  • Always leave your hot tub switched on (unless you’re changing the filter or doing a water change).

Parting advice

And there you have it; now you’re hot tub chemical savvy.

Need more advice? Give us a call on 01482 212322 or email and we’ll help you out. Or drop in and see us in our Hull or Leeds showrooms to see our hot tub chemical range for yourself. 

Not near one of our Yorkshire hot tub showrooms? No problem, if you’re looking for a new hot tub you can explore our virtual showroom or book a video call with our showroom team

Stay up to date with our latest products, hot tub guides and updates on Facebook or Instagram.

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