Do I need to use hot tub chemicals?

hot tub chemicals

A degree in Chemistry probably isn’t what you signed up for when you bought your hot tub. 

Were you promised a low (or no) maintenance hot tub, and now all your time is spent feeling like Doc from ‘Back to the Future’?

Or worse, were hot tub chemicals and maintenance never even mentioned during the buying process?

This blog will help you to understand why you need hot tub chemicals. And simplify the chemistry behind the chemicals, for an easy, no fuss, hot tub maintenance programme. 

Do I need to use chemicals in my hot tub?

 Yes! That’s the short answer.

A good filtration system is the foundation of clean water. It’s going to either make or break your maintenance relationship with your hot tub.

Good filtration will help keep the water safe and clean while reducing the amount of time and money you need to spend on maintenance. A poor filtration system will make the hot tub water hard to manage. And often results in a fall out with the hot tub that leads to you draining it down, and not using it.

But no matter how good your filtration is. Nothing will stop dirt and bacteria coming into your hot tub. Whether it is blown in by the wind. Or comes from the bodies bathing in it. Dirt and bacteria are going to make it into your hot tub water.

And this is where your hot tub chemicals come into play. 

why do I need to use chemicals in my hot tub?

It’s not unusual for people to stop by our showroom to pick our brains about why their newly purchased hot tub water is cloudy. Only for us to discover that their hot tub has never been introduced to chemicals. 

And they’ve used the hot tub since they got it. 

A whole month ago…

Let’s just think about that for a minute.

If you’ve read our blog on filtration (and if you haven’t, you should), you’ll know that, on average, humans lose one pint of body fluid per hour of sitting in a hot tub.


We can practically hear hot tub users around the world jumping out of their hot tub and draining it down. 

Combine that with the fact that a hot tub is bacteria’s version of heaven, with temperatures perfectly conditioned for them to thrive. And you have the potential for your lovely inviting hot tub, to quickly turn into a playground for waterborne bacteria.

If you buy a hot tub from Eagle Leisure you are provided with a complete spa chemical starter kit. But, we’re seeing more and more that this is not the case with all suppliers.

what chemicals do I need to use in my hot tub?

If hot tub maintenance seems like more than you want to take on, you can pay someone to do it. But, it’s easily achievable on your own if you want to save some money and take ownership of your hot tub maintenance. 

Do I need a regular hot tub service?

What do I need to do daily? (or after each use).

  1. Check your pH using test strips. Add pH plus or pH minus as required.
  2. Check your sanitiser levels (Chlorine or Bromine) using test strips. Add sanitiser as appropriate.

What do I need to do weekly?

  1. Use an oxidiser, such as Spa Fusion

What do I need to do monthly?

  1. Clean your filter cartridge using Immerse filter cleaner.
  2. Follow this easy step-by-step guide

What do I need to do quarterly?

TDS (total dissolved solids) is the total of everything that is dissolved in the water (chemicals, debris etc). When the TDS is too high, chemicals are inefficient and the water can look dull and cloudy. The max level recommended is 1500mg/l. Once this is exceeded, it is recommended that you:

  1. Empty down your hot tub. 
  2. Refill your hot tub.

This will occur approximately every 3 months. But this will depend on how often you use it, how many people are using it and how well you are looking after your hot tub water. 

Hot tub maintenance – a step-by-step guide

A simple explanation of hot tub chemicals

If you feel like you need a chemistry degree with all your hot tub chemicals. Fear not. Professor Debbie is here (disclaimer: I’m not actually a professor).

Instructions for each chemical will be on the side of the container.


Simply put. They kill the bacteria.

This is the main thing you will have to check and add regularly. There are two common sanitisers:

  1. Chlorine 
  2. Bromine

Chlorine is the more common, and cheaper of the two. It should sit between 3-5mg/l (ppm). A well-balanced hot tub should not have a strong Chlorine odour.

Bromine is equally effective as a sanitiser. However, it comes into its own in an unstable pH environment. As it is able to effectively kill bacteria even in high or low pH water. 

We usually recommend Chlorine over Bromine, as it is an effective sanitiser that people are familiar with. And it keeps running costs down.

But if you find Chlorine is irritating your skin or eyes. Or, that you are having difficulty keeping your pH stable, we would recommend a switch to Bromine.

What to do if the sanitiser level is wrong

Too high? Let it reduce naturally

Too low? Add Chlorine/Bromine

pH levels

For your sanitisers to work effectively. And for your water to be comfortable to sit it. You will need to check the pH levels. Often people switch off Chlorine, thinking it is irritating their skin or eyes. But it can be an imbalanced pH that causes this irritation.

pH sits on a scale of 0 – 14. With 0 being extremely acidic, 14 extremely alkaline. And 7 being neutral.

The perfect hot tub pH level sits very slightly alkaline between 7.2 and 7.6.

What to do if pH is wrong

Too low? (under 7.2): Add pH plus

Too high? (over 7.6): Add pH minus

Other water balance chemicals

1 Calcium Hardness

Calcium hardness is a measure of how hard or soft water is. Too low and it can be corrosive and cause staining. Too high, and scale will form in the pipework. Calcium hardness should be around 100-200mg/l. 

2 Total Alkalinity

Total Alkalinity (TA) helps to buffer fluctuations in pH. Low TA can cause fluctuations in pH. While high pH can make it difficult to adjust. 

TA should sit between 80-150mg/l/

3. Oxidising

Oxidising your hot tub weekly destroys odours and wastes that are missed during weekly sanitation. It increases the bather comfort and restores the sparkle to the water.

chemical safety tips

Always keep chemicals in their original container and keep away from children. Follow the instructions on the packaging for administering.
Never mix chemicals.

in summary

Chemicals are needed for your hot tub to keep the water safe and comfortable to sit in.

If you don’t want to do some (or any) of your hot tub maintenance, you can hire a local company to do it for you.

You might also find these useful to read:

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Debbie Ekins
Debbie Ekins
Eagle Leisure - Sales & Marketing Manager Mission = to arm you with the knowledge you need to make the best buying decisions. Fuelled by coffee (and naps). Explorer of Scotland and the world.