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Legionella advice for businesses reopening

Many businesses will be reopening from 17 May following closures introduced to help control the spread of coronavirus.

Where a building has been vacant or had significantly reduced usage it is likely that the water supply has also been unused and this increases the chances of bacteria forming.

This is known as Legionella bacteris, and can cause Legionnaires' disease - a potentially fatal type of pneumonia. Legionnaires' disease is caused by water not being used or and becoming stagnated. The bacteria is inhaled through droplets of contaminated water from things like air-conditioning, showers, water sprays, whirlpool or hydrotherapy baths.

Legionella bacteria, commonly found in water, multiply when the water temperature is between 20 and 45ºC.    

It is crucial, in order to protect the health of your customers, visitors and staff, that these risks are identified and addressed. 

Preventative steps

There are steps businesses must take to prevent the potentially-deadly legionella bacteria from getting into their water systems. United Utilities has released information to help this:

  • Hot water systems should maintain water temperatures of at least 60ºC in storage cylinders and above 50ºC through the distribution system
  • Cold water should be below 20ºC
  • Make sure that water systems are flushed through at least weekly. More frequent flushing may be needed for some systems
  • Flush all of the system outlets - it's not good enough to just flush one or two outlets on a large system
  • Reduce the water levels in bulk tanks so there is less standing water
  • Keep records of how you're preventing legionella during closure
  • If evaporative cooling systems are in use, these must be maintained as usual or switched off safely
  • Where water systems have control measures built into the system, these should be maintained and kept working (if feasible) during the closure period
  • It is crucial that businesses have a plan to address the risks relating to re-opening and making sure the water supply is not contaminated.

Where water systems have not been used for a prolonged period, you should take advice from a competent heating/ventilation engineer about pre-start checks and maintenance.

This could include a system service, such as cleaning and disinfection, including cleaning and disinfecting even simple systems such as spray taps and showers before using them again.

Further information

Further information and support can be found regarding water safety in buildings and networks after a period of inactivity via the links below: