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Why Do I Have To Test My Hot Tub Water?

Congratulations on your new Spa or Hot Tub and we are sure that it will give you hours of fun and enjoyment! To ensure that your tub is kept in tip-top condition and everyone using it is kept safe it will be necessary to test and treat the water. We are often asked why do I need to test for and what should I be measuring. Hopefully, the following guide will help:

You need to test the water to:

Why do I Need to Test?

  • Make sure it is safe
  • Make sure it is comfortable
  • Make sure there are enough chemicals
  • Make sure it does not cause damage to the tub surfaces or fittings

What Do I Need to Test for?

Firstly testing should be carried out frequently throughout the day. As the volume of water is relatively small conditions within it can change rapidly. The water should ALWAYS be tested before the first use of each day.

The following should be measured:

Disinfectant: Usually either chlorine or bromine and the levels required should be advised by your supplier. The disinfectant sanitises the water by ‘killing’ bacteria and neutralising waste products. It is essential that this is tested frequently to ensure sufficient is present especially during heavy or continuous use when the disinfectant can be rapidly used up.

pH: This is a measure of how acidic or alkaline the water is. Normally you would be looking for a level of between 7.0 – 7.6. Poor pH control can make the water uncomfortable for bathers, damage the tub and fittings and prevent the disinfectant working correctly

Both disinfectant and pH should be tested several times during use

Total Alkalinity: This is the amount of alkaline salts in the water and acts as a ‘buffer’. Buffering capacity is needed to prevent wild changes in water conditions when chemicals are added – pure untreated water only has a little buffering capacity

Hardness: All water contains hardness and the levels vary depending on your location and the source water. Soft water can be prone to ‘foaming’ where as hard water can lead to scaling and damage to surfaces.

Cyanuric Acid: This only needs to be measured if you are using stabilised chlorines. These contain cyanuric acid (sometime referred to as stabiliser) which is added to ‘hold’ on to the chlorine and prevent it be burnt off by direct sunlight. As the chlorine is used up through normal activity then the cyanuric acid is left in the water. Levels need to be controlled as if there is too much it can cause the chlorine to be locked thus slowing down it effectiveness, the water will look ‘dull’ in appearance and could take on a green hue.

Total Alkalinity, Hardness and Cyanuric Acid should be test at least weekly

How do I test? 

There are lots of test systems available and whichever one you select it is important that you understand how it works and that you are able to read the tests. We would recommend that you use a tablet based systems as:

  • These are easier to read and colours do not run into each other
  • The tablets are individually sealed so you know the last test is as good as the first
  • You will be using the same test chemistries as used by the professionals

Remember the more testing you do the safer the water, the better it will be for tub and the more control you will have on chemical use.

Testing Options from Lovibond

For more information on hot tub testing from Lovibond please view the following:

DescriptionCodeMeasures Suitable for
Domestic PoolTesters & Hot Tubs Kits    
Pool & Hot Tub Test Kit158010Cl 0.5-6mg/l
Br 1.1-13.2mg/l
pH 6.8-8.2
hot tubs
Traditional Cl/pH PoolTester (Orange Box)151601Cl 0.5-6mg/l
pH 6.8-8.2
hot tubs
5in1 Multi PoolTester151900Cl 0.1-3mg/l
Cya 20-200mg/l
TA 20-800mg/l
CaH 20-800mg/l
hot tubs
Tablet Refill Pack 5in1 PoolTester515980  1515900
Electronic PoolTester Scuba II216100-17Cl 0-6mg/l
Br 0-13.5mg/l
pH 6.8-8.4
Cya 1-160mg/l
TA 0-300mg/l
hot tubs
Professional Instruments    
MD100 3in1 Photometer278011Cl/pH/Cya pools
hot tubs
MD100 3in1 Photometer278060Cl/pH/Alk pools
hot tubs
MD100 3in1 Photometer278110Cl/pH/Br Hot Tubs
using chlorine or bromine
MD100 6in1 Photometer278091Cl/pH/Br/Cya/TA/CaH  
MD110 6in1 Photometer2980902Cl/pH/Br/Cya/TA/CaH With Bluetooth

Pool and hot tubs choline testing systems from Lovibond.
Abbreviations used: Br = Bromine, CaH = Calcium Hardness, Cl = Chlorine Cya = Cyanuric Acid, TA = Total Alkalinity

For further information on regulations and legislation please use the following links:

Camlab can supply a comprehensive range of test kits for swimming pool and hot tub testing. Please contact us for further information.

This blog article was supplied by the technical department at Lovibond.

2 thoughts on “Why Do I Have To Test My Hot Tub Water?

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