Water Treatment Testing For Cooling Towers


Frequent, accurate testing of the water in your evaporative cooling system is vital in order to maintain the water quality, lifespan and safety of your system.

There are various tests and checks needed, most are basic and easy to carry out although some are more complicated. There is no reason why a site team can’t carry out some or all of the tests in-house provided they have the time and the expertise. Most sites opt to carry out the simple, frequent tests in-house and rely on an expert service provider for the more in-depth tests.



Water treatment programmes are an expensive investment – you need the chemical dosing to help prevent corrosion, scale formation and bacterial problems, but it comes at a cost. Unless the chemicals are used correctly and the water chemistry is kept under control, major problems can occur with serious cost and safety implications.



Some tests and checks are needed frequently because, things can go wrong quickly, and the consequences can be severe. The priorities are:

  • Water softener (if you have one) – basic checks for power, salt and soft water
  • Cooling water conductivity – this checks that the system bleed is working properly
  • Cooling water primary biocide (usually bromine or chlorine) – checks that this chemical is dosing properly
  • Cooling water pH – this checks that the water is not corrosive, and is in the correct range for the biocide to work properly
  • Cooling water bacterial levels – usually tested using a dipslide

These tests are normally carried out at least weekly.

Other important tests are carried out less frequently – here’s the guidance from the HSE (table 1.8 page 41)



Carrying out water treatment tests can be simple – if you know how.

You can access content online (YouTube etc) but the quality is variable.

If you have a good water treatment service provider, they should be able to provide some basic training (toobox talks) or more in-depth sessions to meet your needs.

Or you could access an external course such as:





Cooling_Open-Closed_Water_Test_Kit_You can get the testing equipment you need from a number of good suppliers




If you’re not sure exactly what you need, a good supplier will support and advise you.




compli appPart of the cost of your programme is for your provider to produce reports showing test results, summary reports, recommendations etc, and for a system to keep the records in. This should be user-friendly – you need to be able to access this information to manage the system, and you may need to call upon it as evidence of compliance.



Keeping records of all test results is really important as it helps to recognise and diagnose problems before they escalate.

If you are paying for a comprehensive record keeping system – make sure you understand it and can make use of it, otherwise consider a simpler more cost-effective system.



  1. Invest in getting your testing set up properly – get the right training and equipment
  2. Work in partnership with your service provider – decide who is carrying out which tests
  3. Review your results – keep good records and use them to look for problems and potential improvements
  4. Congratulate yourself and enjoy the peace of mind!



This table shows the most common tests you need to carry out. There will be variations based on each system and site, but this is a basic guide. There will also be maintenance checks needed such as checking the salt level in the softener brine tank, checking system cleanliness and checking dosing equipment is working properly


Test Make up Water / Softener Cooling System Water
pH Monthly Weekly
Conductivity Monthly Weekly
Oxidising Biocide Weekly
Bacteria Level (Dipslide Quarterly Weekly
Calcium Hardness Monthly Monthly
Inhibitor Level Monthly
Alkalinity Monthly Monthly
Chloride Monthly Monthly
Iron Monthly Monthly
Legionella Analysis (Laboratory) Quarterly
Concentration Factor (calculated) Monthly
Calcium Balance (calculated) Monthly


LSI (calculated) Monthly