An Update of any Building Shutdown or Low Occupancy during the COVID-19 Outbreak

We have now been given a further update from the Legionella Control Association and HSE who have advised the following: -

The Health and Safety and Work Act still applies and Dutyholders must be taking reasonably practicable steps to control the risks from Legionella throughout this time.

Dutytholder’s implicated in an outbreak of Legionnaires’ disease resulting from actions taken for COVID-19 precautions are not likely to have any exemption from prosecution.

We therefore strongly recommend that any Hot and Cold-water Systems in buildings that are empty or with under occupancy must address the issue of stagnation:

  1. If the building is still partially in use, take additional measures to keep the remaining occupants safe
  1. If possible, drop the stored water level in the tanks to maintain <24 hours storage
  2. Flush all outlets to simulate use – weekly flushing may not be sufficient, this may need to be increased to twice weekly or even daily if possible.
  3. Temperature monitoring to ensure that thermal gain in cold water is controlled.
  4. If controls are lost (temperatures, biocide levels etc.) the guidance from HSG274 is to sample for Legionella Weekly.
  5. Consider other short term measures to keep remaining occupants safe, such as fitting point of use filters at designated locations with other areas shut off.
  1. Buildings that are temporarily shut down (mothballed) should follow the guidance in HSG274 Part 2 Paragraphs 2.50-2.52
  1. Do not drain down pipework.
  2. If possible, remove sources of heat and external thermal gain.
  3. Lock off, place signage on doors and otherwise advise potential users the system has been taken out of use.
  4. Have a plan in place for recommissioning the water system 

Recommissioning Water Systems

It is essential when buildings reopen, following the lifting of COVID-19 restrictions, that any water system is not simply put straight back to use.

During the period of shutdown, it would be sensible to formulate a recommissioning plan for each water system to allow safe start-up and assurance to users that it is safe. Please feel free to contact us should you require any advice at any point for this.

The minimum expectation for small, simple hot and cold water systems would be flushing through with fresh mains water.

Larger buildings, those with cold water storage tanks, showers, calorifiers and more complex pipework- the expectation is likely to require a far more extensive flushing regime, followed by a system cleaning and disinfection.

During flushing, ALL valves should be operated in the fully open position so that any particulate matter can be flushed through.

Where buildings have been empty for some time and during warmer weather, it is likely that some increase in bacteria levels and biofilm will occur. These water systems may require more than a simple disinfection and may even require two.

From a microbiological perspective, the period between filling the system and bringing it into normal use is potentially the most hazardous. A risk assessment should be performed before commissioning, to identify and take into account the potential for stagnation as this may lead to microbial growth where buildings are not to be fully occupied immediately or where systems are commissioned as occupation occurs, eg infrequently or intermittently used buildings.

In all cases where systems are being recommissioned it is sensible to have evidence to prove/reassure that the recommissioning process has been effective. Sampling at this point should be considered to validate the effectiveness of this process (should be taken 2-7 days following recommissioning and not on the day).

There is a potential for multiple outbreaks of Legionnaires’ disease following the COVID-19 outbreak, if actions taken now are not carefully considered.

If you require any help with recommendations and advice when the time comes to recommission your building(s) water system(s) please do not hesitate to get in touch 01743 247942 or email