Water systems and legionella

Legionella bacteria can cause serious illness, such as Legionnaires' disease. Which is a type of pneumonia. It can also cause other types of flu-like illness such as Pontiac fever.

Where legionella is found

Legionella bacteria is usually found in water, such as rivers and ponds. It's also found in purpose built water systems, such as:

  • hot and cold water systems that supply sinks and showers with hot and cold water
  • cooling towers
  • evaporative condensers
  • spa pools

Health risk

When legionella bacteria is in the right conditions to grow, it can become a health risk. This rarely happens in natural environments.

Closed or limited use of buildings, such as offices, can create the right conditions for legionella to grow in water systems.

If you manage your water systems well and have the right controls in place, you'll be able to keep them safe.

Find out more about legionella and workplace risks.

Employer responsibilities

If you're an employer, or someone in control of a premises, such as a landlord, you have a duty under health and safety law. This duty is to understand and manage legionella risks.

You must carry out risks assessments on all water systems. Not all systems need elaborate control.

Returning to work

When you return to your place of work you need to check your water system. You must follow the key actions below if you’ve been away for more than one week:

  • Run taps starting with the one nearest to where the water pipe enters the building. Make sure the water is clear and feels cool to the touch.
  • Empty cisterns and refill with fresh water from the incoming supply. Flush through the taps before use.
  • Rinse shower heads through before use. We recommend you wear a face mask when carrying out this task.
  • You must take precautions to reduce the risk of Legionella, such as removing the shower head before flushing. See more tips on hse.gov.uk
  • Thoroughly flush through all appliances connected to the water supply before use. Use the manufacturer's instruction manual.
  • Check the property's internal filters or water softeners to make sure they are working correctly, as outlined in the manufacturer's instruction manual.
  • Use approved plumbers to make changes or repairs to plumbing systems. Find your local approved plumber on WaterSafe
  • Use water wisely whether you’re at home or at work. Leaks can waste lots of water and be costly. Check your plumbing and toilets regularly. We are expecting high demand this summer and with your help we can save water for when it’s needed most.

See top tips for saving water in your business

Find out more about checking inactive water systems

Find out more about legionella

Legionnaires’ disease: A brief guide for dutyholders
Legionnaires' disease. The control of legionella bacteria in water systems

Contact the food and safety team

For more information email: foodandsafety@medway.gov.uk