Exposure to legionella bacteria happens when airborne water droplets are inhaled. This could lead to Legionnaire’s disease, which is a potentially fatal type of pneumonia. But this can be preventable through sensible risk assessment and appropriate testing.

Storage tanks, along with hot and cold water systems, whirlpools and atomisers, happen to be one of the potential sources of risk for legionella. But minimising, if not eliminating your risk for exposure to the bacteria, will need more than just getting a storage tank testing kit from a legitimate provider.

Since legionella bacteria thrive in certain temperatures, between 20-45°C, you will want to monitor and maintain your water temperature to prevent bacterial growth. The Health And Safety Executive recommend the following temperature controls:

  • Cold water storage and distribution below 20°C
  • Hot water cylinder storage at 60°C or higher
  • Hot water distribution at 50°C or higher


Aside from specific temperatures, stagnation is also one of the key factors to legionella growth in water systems. And cold water storage tanks are prone to stagnation, making these systems a high risk.

Managing this risk involves regular inspections and the use of testing kits to get samples. It is crucial that someone has to be responsible for this task, whether it’s for a residential property or for a commercial establishment.

Inspections must be carried out expertly and recorded accordingly. Samples must be taken as detailed by the testing kit.

To make sure that your samples will be tested thoroughly, ask your testing kit provider about its laboratory. An accredited laboratory should test the samples so that your screening is effective.

To address stagnation, dead legs or dead pipes should be taken out from pipe work; infrequently used outlets should also be flushed, cleaned, and descaled regularly. The HSE recommend doing this once a week.

Prevention or control could be achieved by looking at the type of water system you have. In most cases, a change in design might be in order to get the storage tank up to standard and keep legionella bacteria from multiplying.

Overall, following a set of guidelines when it comes to legionella screening and having the right testing kits, backed by an accredited laboratory, would help you keep your storage tanks free and clear of the deadly bacteria. For commercial establishments that cater to the elderly and those with compromised immune systems, it is crucial to keep records of the steps taken to prevent or control the risks. This provides reference for the frequency of inspections and testing to be done.  

Written by: +Duncan Hollis