Water Management for Legionella

Water is used for a wide variety of applications including:

  • Services such as showers, taps, toilets etc
  • Heating
    • Comfort heating for buildings
    • Heating or cooking in a manufacturing process
  • Cooling
    • Air conditioning
    • Cooling in a manufacturing process
  • Washing / Cleaning


One of the main problems found in water systems is bacterial growth.


Bacteria are naturally occurring in water systems and will multiply into very high numbers given the right conditions. This can present a health hazard, particularly Legionnaires Disease, as well as causing slime build up in the system. Reduced flow rates, blockages and corrosion are all common problems. Bacterial levels can be controlled using the right combination of filtration, biocide chemicals and cleaning.



The main concern with bacteria is the potential health risk. Most bacteria are harmless, but some can cause diseases – these are called pathogens. The risk of Legionnaire’s Disease is well documented – there is excellent guidance from the HSE here https://www.hse.gov.uk/legionnaires

Other problems in the water system such as scale and corrosion increase the risk of Legionnaire’s Disease.



By law, employers must assess and control the risk of Legionnaire’s Disease. This means carrying out a detailed and specific risk assessment, then setting up a control scheme of actions (written scheme). These actions could be simple, such as inspecting water systems for cleanliness and recording the findings. A more complex control programme including dosing chemical disinfectants (biocides) and taking samples for laboratory testing may be required for a system which presents a high level of risk such as an evaporative cooling tower.



It is vital to record the findings of your risk assessment and risk control actions (written scheme). This can be done using a paper log book, or using a database or on-line system. The records should clearly show the results of tests and inspections carried out as well as the follow up remedial actions taken to rectify any problems.



Your risk assessment and written scheme should be reviewed regularly and when anything changes such as modifications to water systems or changes to the use of buildings. Regular reviews help to keep your risk control system up to date and effective.