Legionella Control (HSE)

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Temperature control is the primary method used to control the risk from Legionella.

Water services must be managed and controlled at suitable temperatures that will prevent Legionella Proliferation (growth) such as:

  • Hot water storage cylinders (calorifiers) should store water at 60°C or higher
  • Hot water should be distributed at 50°C or higher
  • Cold water should be stored and distributed below 20°C.
  • Thermostatic mixer valves (TMV) need to be fitted within 1.5 metres of the outlet it supplies.

Your Legionella Control (HSE) manager should frequently inspect, monitor and maintain the water system, in accordance with the site risk assessment.
Sentinel outlets (nearest and furthest to stored hot and/or cold water) should be identified so that monthly checks of distribution temperatures can be carried out. Stored hot water temperatures should also be checked and reviewed every month and stored cold water tank temperatures at least every six months.

As stagnant water provide Legionella bacteria an ideal environment for growth, dead legs/dead ends in pipe-work should be removed. Infrequently used outlets, (especially aerosol generating outlets such as showerheads) should be flushed on a weekly basis. All outlets that generate a spray (showers and spray taps) should be cleaned and descaled on a quarterly basis. Cold-water storage tanks should be cleaned periodically and all water should be drained from hot water cylinders to check for debris or corrosion.

Water sample analysis can be used as an additional control method for systems that are presenting temperatures out with the control parameters.

FAQ’s

How do I control the risks from legionella in my water system?

The key point is to design, maintain and operate your water services under conditions that will either prevent or adequately control the risk from legionella bacteria. It is important that you either have, or have access to, competent help to fulfil these obligations.

If you identify a risk that you are unable to prevent, you must introduce appropriate controls. You should introduce a course of action that will help you to control any risks from legionella by describing:

  • your system and its component parts eg developing a schematic diagram
  • who is responsible for carrying out the assessment and managing its implementation
  • the safe and correct operation of your system
  • what control methods and other precautions you will be using
  • what checks will be carried out to ensure risks are being managed and how often

You should where appropriate:

  • ensure that the release of water spray is properly controlled
  • avoid water temperatures and conditions that favour the growth of legionella and other micro-organisms
  • ensure water cannot stagnate anywhere in the system by keeping pipe lengths as short as possible or by removing redundant pipe work
  • avoid materials that encourage the growth of legionella (The Water Fittings & Materials Directory references fittings, materials, and appliances approved for use on the UK Water Supply System by the Water Regulations Advisory Scheme)
  • keep the system and the water in it clean
  • treat water to either control the growth of legionella (and other microorganisms) or limit their ability to grow.
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