Skip to content

Email: Tel: 0115 8882726

Water Treatment for Hot Tubs- The Basics

Water Treatment for Hot Tubs

It’s important to ensure that the water in your hot tub is clear, clean and hygienically safe, this is because there could be harmful micro-organisms that could case problems if they are left unchecked.  So, its vital that the water is treated to BISHTA standards.

The good news however is that its neither expensive nor time consuming as these days there is a wide choice of water testing treatment products, which are safe, easy to use and most importantly reliable.

The most common and important types of water treatment products are sanitizers(disinfections), oxidizers, minerals and pH balancers.  Now we are going to go into more detail about the different types of water treatment.


It is recommended that residual sanitizers are used continuously. This because the residual sanitiser kills harmful micro-organisms rapidly and leaves the residual in the water.


This is a fast and effective sanitiser, and its biocidal properties are well established and proven. There are two different types of Chlorine granules which are available for use in hot tubs, safe and easy to use. There is calcium hypochlorite which is unstabilised free and available in a quick dissolving form. Then there is sodium dichloroisocyanurate dehydrate (troclosene sodium, dehydrate or “dichlor”). This stabilised chlorine and helps keep chlorine in water on a warm sunny day. Stabilised chlorine tablets are also available but some manufactures of hot tubs state that their use will invalidate the warranty.  


Bromine is also available. It’s a popular with hot tub owners as it doesn’t give off a swimming pool odour that is associated with chlorine, and its effective at higher temperatures. Bromine is sold in granule, lozenges or tablets form.


PHMB (which is also known as Biguanide) contains neither chlorine nor bromine. It destroys bacteria by assaulting the cells walls of the microbe. PHMB emits less odour than either chlorine or bromine and does not cause smell at high temperatures found in hot tubs.

Note: PHMB is not compatible for use with chlorine or bromine and correct advice must be sought.


pH balancers

For your sanitiser to work effectively and for the comfort of bathers and protection of the hot tub equipment that pH in the water must be controlled. pH in the most basic term is the balance between acid and alkaline substance in the water. So, if the water is too acidic, then the water will be become corrosive, and if its too alkaline than there is a possibility for damaging scale to form.

pH balancers are water treatment products which allow you to easily and safely control. pH balancers that need to be added gradually to achieve the correct levels of pH.  

Acids or pH reducers: used to lower a high pH

Alkalis or pH increasers: used to raise low pH

T.A increases: used to increase the total alkalinity. Total alkalinity is a measure of the total amount of alkaline substances in the water. If it’s too high then it will make an incorrect pH difficult to adjust, and if its too low than small additions of with pH reducer or increaser will cause the pH to swing one way or the other rapidly. So the correct T.A acts as the buffer against this and allows you to control the pH easily, quickly and effectively.



For you to know whether you are treating water correctly and whether it’s safe and hygienic to use, its important to test the water in your hot tub daily before use to find out what the pH and sanitiser levels in the water are. Once you have tested the water you will need to make any adjustments that are required buy the results of the test.

There are several of inexpensive test kits on the market which are quick, safe and reliable to use. Testing just takes a few seconds, whether by tablet type test kits-where the tablets which change colour according to the readings  are dropped in a sample of the hot tubes water, or by test strips-which are small strips with impregnated pads which change colour when dipped into the water.

Note: both test strips and test tablets have used by dates. It’s important that you only use test strips and tablets that are in date.


Recommend test reading parameters.

Here are the recommended levels that your hot tub water should be.

Bromine (if being used as your sanitiser)

2mg/l – 4mg/l Domestic   4-6 mg/l Business

Chlorine (if being used as your sanitiser)


PHMB (if being used as your sanitiser)




Total Alkalinity

80-120 mg/l


Subscribe to our newsletter

A short sentence describing what someone will receive by subscribing

International Delivery

For small orders & export tenders

12,000+ PRODUCTS

From the Market Leaders

Support & Trade Accounts

Contact Us for Support & Trade Accounts

Secure payments

Online payments securely administed by Shopify