Hot Tub Water - Closeup detail of jets at maximum.

The Hot Tub Chemicals Guide

Are you unsure of what chemicals you need to maintain and clean your hot tub, spa or pool? Or maybe you’re a new hot tub owner and you are unsure of the right chemical dosage amounts that you require. Whatever your needs, here at SpaChem we have got you covered with our how-to guide.  As hot tub chemical experts, at SpaChem we only supply products that have been extensively tested and have been designed for quality use on hot tubs, spas and swimming pools. As well as this guide, it’s important to refer to the instructions and warnings that are on the products you are using. 

The 3 Simple Steps Guide

If you are setting up your new hot tub or spa, take a look at simple steps to get you started. 

Add commissioning or normal shock doses of chlorine

After you have filled your hot tub with water and before using it for the first time, you will need to add an initial shock dose, this will help to remove any bacteria and increase the time you have until the water needs replacing (in this time you will also need to regularly maintain the water with chemicals).


Test the water

You will need to wait for 24 hours, then you can test the water. You can use test strips to test the water and before you do this, make sure that the chlorine, pH and total alkalinity levels are balanced before using the hot tub. You may also need to adjust them before testing and the dosage amounts may vary.

Practice a regular maintenance procedure

To help you to maintain a healthy hot tub that is clean and healthy, we recommend that you start a hot tub cleaning and maintenance regime. You can list tasks that will need providing on a daily, weekly and monthly basis. One of the easiest things that you can do is to always test the water before you use your hot tub, you should then make the necessary adjustments to the chemical levels as and when you need to.

Your Chemical Care Routine

Daily Chemical Cleaning

As mentioned earlier, you should list and provide the necessary tasks and duties that you will need to carry out in your hot tub or spa.

Keep your filter on

We advise that when it comes to the hot tub water, it is filtered for a minimum of 4 hours a day, if you leave your hot tub on, the filter cartridge will collect any suspended dirt or oils.

Test chemical levels before use

You should always make sure that hot tub and spa chemicals are balanced. This is to maintain clean and healthy water. If your chemicals aren’t at the right levels, this could be the chlorine, alkalinity or pH levels, then your hot tub or spa won’t be functioning safely.

Check the filter cartridge

Filter cartridges should be removed and cleaned after every use, every few weeks or after the hot tub has had lots of use, you should replace the filter cartridge with a new one. You should also look out for discolouration or stiffness.

Check out our top tips of how you can clean your hot tub filter:

  • Make sure that your pump is switched off.
  • Remove the complete hot tub filter housing from the hot tub or spa.
  • Remove the filter housing and cartridge.
  • Wash the cartridge with the hose or cold tap water and then leave it to dry. Don’t use any detergents to clean the filter.
  • Next the filter will need replacing, do not use a wet filter cartridge as this won’t work properly.

Weekly Chemical Cleaning

Every week there are certain activities that you will need to provide in order to prolong the life of your Lay-Z-Spa’s water.

Shock dose if used often

Hot tubs are smaller in size than swimming pools, they will be shared by more people which means a lot more contaminants will be brought into the water. We recommend that you provide a shock treatment to the water once a week especially during frequent use. During periods of less use, the hot tub or spa may not need to be shocked as often,  but you will still need to keep an eye on the water quality, clear water doesn’t always mean clean water. 


Clearwater clarifier, this includes flocculants that stick small particles of debris and algae together, this will make it easier for your spas filtration system to monitor the water and keep it clear.

Monthly Chemical Cleaning

Every month you’ll need to provide the following in order to maintain water hygiene.

Replacing the water

The amount of water changes will reflect the extent of use of the hot tub, this will also affect the chemical testing. If chemical levels aren’t at the usual ranges or if you seem to be losing a lot of water, it’s advised that you replace all of the water, retreat and retest again before use.

Impromptu Cleaning

This refers to particular chemical reactions in the hot tub water.

Foam Remover

We advise that you shower before using the hot tub, this is to help reduce the amount of residue from products including shampoo, deodorant, detergent, sun cream, make up, fake tan and any other natural boiler oils. All of these things can cause chemical imbalances, we know that showering may not be able to fully remove all of these substances and some that are still present may react with the water. To prevent this, you can use a foam remover in the water.

Should you require any more information or have any questions regarding your hot tub chemicals, contact the SpaChem team today.

Chemical Doses and Measurements

Here we advise on how to shock dose your hot tub, as well as adjusting Chlorine, pH and Alkalinity levels.

Total Alkalinity (TA) is measuring your hot tub water’s ability to neutralise acids, a Balanced Total Alkalinity will help to control the pH levels, the accurate level to aim for is around 80 to 120 parts per million (ppm).

Balancing Alkalinity Levels

  1. You should dip a test strip into the centre of your hot tub, take it out then hold it still for around 15 seconds.
  2. Compare the test strip against the colour chart that came with them.
  3. Total Alkalinity results:
chlorine levels

Low TA levels that are below 80ppm, mean that a Total Alkalinity Increaser is required, when it comes to the amount of TA that you need to add to your hot tub, this will all depend on the volume of water, as well as how low your readings are. A hot tub that holds 1000 litres will need 18g in order to raise Total Alkalinity levels by 10ppm – 10 parts per million. 

High TA levels that are above 120ppm will require a PH Minus, the amount of pH decreaser that you will need to add to your hot tub will depend on the levels as well as the volume of water. You can check the dosage rates on the back of the bottle and measure this accordingly. 

Issues from Unbalanced Total Alkalinity Levels

When it comes to balancing total alkalinity levels in your hot tub, this can cause a number of problems including affecting your spa experience

High Total Alkalinity

  • A build up of scale, cloudy unclear water, clogged filters, weakened hardware and irregular pH levels
  • Burning eyes and itching skin
  • Unsanitary


Low Total Alkalinity

  • A build up of scale, green coloured water, irregular pH levels and low water quality
  • Metal corrosion such as the pump
  • Burning eyes and itching skin
SpaChem 7kg pH & Alkalinity Reducer

pH Balance

pH measures how acidic or alkaline your water is, the correct range of hot tubs tends to be between 7.2 and 7.6, balanced pH is required for other chemicals to work properly and an imbalance pH level could affect your hot tub components and in some cases cause skin irritation. 

How to balance your hot tub pH levels

  1. Dip a test strip in the centre of the hot tub, take it out and hold it still for 15 seconds.
  2. Compare the test strip results with the colour chart.
  3. pH results:

For low pH levels that are below 7.2, you will need to use a pH plus to help you to raise the pH levels and balance the water again.

High pH levels that are above 7.6 will require a pH minus to help bring the levels back down.

The pH increaser or decreaser that you will need to add to your hot tub will depend on the amount of water as well as how long your readings are, we advise that you refer to the dosage information, this will be printed on the individual chemical bottles.

Issues from unbalanced pH levels

pH measures how alkaline or acidic your water is, we recommend making sure that your hot tub pH levels are balanced between 7.2 and 7.6, this will avoid affecting your spa experience negatively. 

High pH readings

  • Eye and skin irritation
  • Dull, cloudy or foamy water
  • Scale
  • Low sanitation
  • Shorter filter runs


Low pH readings

  • Dry, itchy skin and eye irritation
  • Hot tub components corrosion
  • Frequent filter changes
  • Less effective sanitisation 
  • Impacts total alkalinity 


Chemical levels in your hot tub will be influenced by different causes and may provide varied results. The number of people using the hot tub, the water hardness and other elements including leaves, grass and mud will all have an impact on the chemical requirements. At Spa Chem, we advise that you always re-test the water before you use your hot tub.


Chlorine is a sanitiser, it controls and prevents the growth of bacteria, it is required for the hot tub water to be clean and safe to use, recommended chlorine levels in hot tubs are 3-5ppm. Balancing Chlorine levels
  1. Dip a test strip in the centre of the hot tub, take it out and hold it still for 15 seconds.
  2. Compare the test strip results with the colour chart.
  3. Chlorine level results:
  For low chlorine results that are below 3ppm, you’ll need to add the right amount of chlorine to help restore the balance. See the instructions that are included with the chlorine granules or multifunction chlorine tablets packaging. If the levels are low you will need to shock dose the hot tub. High chlorine levels that are above 5ppm will involve draining the spa to the minimum mark and then refilling it with fresh water to the maximum mark. This will help to dilute the chemicals, you can also remove the cover from the hot tub, this will permit it to evaporate. 

Issues with unbalanced Chlorine

It’s important to ensure that your hot tub chemicals are correct, not enough chlorine will create an unhygienic bathing condition and high chlorine can cause irritation to your eyes and skin. 

High Chlorine levels

  • Low sanitation
  • Damage to components and parts
  • Itchy eyes that may also turn red and a skin rash

Low Chlorine levels

  • Poor sanitation
  • Cloud and unclear water
  • Bacteria growth
  • Horrible smell

All About Shock Dosing

These are the situations where shocking dosing is necessary:

  • When you first use and fill the hot tub up with water
  • Should you notice algae or slimes
  • After it has been used frequently
  • Low water clarity or quality
  • After a long period without use
  • When you refill it with fresh water

Chlorine tablets should only be used for keeping chlorine levels stable, tablets are slow dissolving and won’t have the same impact as granules.

You can use your hot tub when the chlorine level is between 3 and 5ppm, you should allow at least 24 hours for these treatments to dissolve and be safe to use.