• Find the Legionella risk assessment for your building
  • Restart hot water systems 24 hours before the building is to be reoccupied
  • Test water temperatures
  • Get expert advice if a building’s occupants’ health places them in a high-risk category

Commercial hot water and heating specialist, Adveco, today offered a precautionary warning against the dangers of Legionella for businesses planning to open facilities under the Government’s ‘conditional plan’ to reopen society.

“In response to Covid-19, an unprecedented number of business properties have been forced to close, often with little to no warning. As those businesses work towards reopening it is extremely important that some consideration is made to how to restart it without creating an unsafe situation if buildings have been shut and the hot water has been turned off,” advises Bill Sinclair, technical director, Adveco.

“Stagnant (not moving) water, especially at warm temperatures (more than 20°C), creates the ideal situation for the proliferation of Legionella bacteria.  Normally in hot water systems the risk is minimised by the temperature, constant flow and because the risk of Legionella in the incoming mains is relatively low. However, it can be present, and the risk to building occupants increases if: a water system is fed from a cold water tank instead of the mains; a hot water system has been turned off for more than a week; there are aerosol creating taps such as showers, whirlpool jacuzzi hot tubs, washing up spray faucets, and any building where occupants are elderly or immunocompromised.”

If a business has been closed, and the hot water system has been off, and the building taps are mains-fed and occupants are low risk and then it should be sufficient to do the following:

  • Find the Legionella risk assessment for your building and read it thoroughly
  • Start up your hot water system at least 24 hours before the building is to be occupied
  • Make sure all pumps are on
  • Make sure the hot water temperature is over 60°C

Wait a few hours, or better still next day carry out the following:

  • With a thermometer, check the temperatures from several non-blended taps that are as far as possible from the water heating system. They must achieve temperatures of more than 50°C within 60 seconds, and preferably hotter and faster
  • Run all hot and aerosol creating taps to thoroughly flush them. The minimum expectation for small, basic hot and cold water systems would be flushing through with fresh mains water.  During flushing, all valves should be operated in the fully open position so that any particulate matter can be flushed through. For larger buildings with tanks, showers, calorifiers and more complex pipework, more extensive flushing is recommended. Due to the recent warm weather, it is likely that some increase in bacteria levels and biofilm will occur. Depending on circumstances, sampling and testing for different bacteria may be recommended and the system will require cleaning and potentially repeated disinfection.

If your hot water system has been off, and your building taps and occupants are medium or high risk then you must do the following:

  • Find the Legionella risk assessment for your building and read it thoroughly
  • If you have a maintenance team with expertise in Legionella you should contact them before restarting the hot water system
  • If you do not have such a team you must take advice from a firm that does or contact Adveco Technical Support for further information