Legionella risks for buildings which had been “moth-balled” during the coronavirus outbreak

As buildings start to reopen, following a period of being closed or reduced occupancy during the coronavirus (COVID-19) outbreak, it is imperative that any water system is not just switched back on without considering the principles of what to do to control Legionella.

Water system stagnation can occur due to lack of use, increasing the risks of Legionnaires’ disease. The JC Groups have been working closely with their clients to carefully manage the reopening of their water systems in a safe and responsible manner. JC Groups Director, Nicole O’Callaghan states,

“My worry at the beginning of lockdown was the potential for multiple outbreaks of Legionnaires’ disease following the COVID-19 outbreak if actions taken to reopen, are not carefully considered.

We’ve had several surprising cases where sites with very low risk water systems have had positive legionnella samples with unexpected elevated levels. This is particularly worrying considering the low risk nature of the water systems involved.

I am now very concerned about any retail property or building, that has been closed during lockdown, being affected by Legionella proliferation.

Without intending to scare monger at a time that is already stressful enough, I feel it is our duty as a water hygiene specialist & FM contractor, to urge anyone who is the dutyholder of a building, to consider this risk. I would also advise that if you are unsure, to seek advice from a competent person and/or specialist, to help identify and implement suitable controls for managing this risk.”

The Legionella Control Association (LCA) are supporting their members such as The JC Groups by providing guidance during this unprecedented time with the below guidance.

LCA Guidance

As LCA Members, The JC Groups can provide the following guidance. Each Dutyholder must make their own determination for each circumstance but the following principles should be considered when making decisions on what to do to control legionella during the COVID-19 outbreak:

1) The expectation for evaporative cooling systems is that they will be maintained as usual or switched off safely – there is no leeway in this

2) The expectation for water systems supplying critical services, for example hospitals, is that they will be maintained as usual – there is no leeway in this

3) Hot and cold water systems in buildings that are empty or with under occupancy must address the issue of stagnation:

a. If the building is still partially in use take additional measures to keep the remaining occupants safe:

i. If possible, drop stored water levels in tanks to maintain <24 hours storage

ii. Flush to simulate use – weekly flushing may not be sufficient

iii. Monitor temperature to ensure thermal gain in cold water is controlled

iv. If fitted, consider temporarily increasing levels of potable water treatment dosing – consider other consequences of this such as corrosion and make the decision on balance of benefit

v. If controls are lost (temperature, biocide levels, etc.) the guidance in HSG274 is to sample for legionella weekly

vi. Consider other short term measures to keep remaining occupants safe such as point of use filters at designated locations with other areas shut off

b. Buildings that are temporarily shut down (mothballed) should follow the guidance in HSG274 Part 2 paragraphs 2.50-2.52:

i. Do not drain down pipework 

ii. If possible, remove sources of heat and external thermal gain

iii. Lock off, place signage on doors and otherwise advise potential users that the system has been taken out of use

iv. Have a plan in place for recommissioning the water system

For all of the work above there should be a task risk assessment in place to ensure operatives are workig safely.

Recommissioning Water Systems

It is essential that when buildings reopen following the lifting of COVID-19 restrictions, that any water system is not simply put straight back into 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.  Dutyholders are likely to be able to access competent help from service providers remotely during the period of restricted movement.

Any plan for recommissioning buildings must take into account the safety of the operatives carrying out the work.  It is foreseeable that the hazard present within water systems in this situation would be greater than normally expected.  Reasonably practicable measures such as limiting aerosol, minimising exposure and use of RPE should be considered.

Evaporative cooling systems should already have robust start-up and shut-down procedures in place and the expectation is that these will be followed.

The minimum expectation for small, simple hot and cold water systems would be flushing through with fresh mains water.  Larger buildings, those with tanks, showers, calorifiers and more complex pipework the expectation is likely to be for more extensive flushing followed by cleaning and disinfection.  

During flushing all valves should be operated in the fully open position so that any particulate matter can be flushed through. Of particular importance are float-operated or other restrictive valves which need to be manually opened to ensure clearing of particulates and prevent fouling of the valves. Where a clearing velocity cannot be achieved, consideration should be given to removal of valves to enable an effective flush.

Where cleaning and disinfection is carried out, it is very important to monitor the decrease in disinfectant level over the course of the contact time.  Loss of more than 40% disinfectant concentration could indicate influence of biofilm.  See BSI PD855468 for more guidance.  

Where buildings have been empty for some time and during warm weather, it is likely that some increase in bacteria levels and biofilm will occur.  These water systems may require more than a simple disinfection at 50ppm of chlorine for an hour to be successful.  Be prepared for the need to repeat some disinfections to achieve success.  Manage customer expectations and be careful to agree the process rather than guarantee the result.

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 to BS7592 should be considered for recommissioning plans to validate the effectiveness of the process.  As per HSG274 part 2, samples should be taken 2-7 days following recommissioning and not on the day of disinfection.  Follow up samples may need to be considered as part of the recommissioning plan.

While each individual water system is likely to need individual consideration, it will be helpful to be aware of the bigger picture with regard to demand on services.  There will be an increased demand for flushing and disinfection, sampling and other system recommissioning work.

Need some help?

The JC Groups can assist with any plans for the recommissioning of water systems and are happy to answer any questions you have and start the necessary planning. There is also some very helpful guidance and advice at:

The HSE have guidance on Legionella Risks During the coronavirus outbreak.

The Legionella Control Association has published guidance on managing water systems during the coronavirus outbreak.

The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Legionella Infections (ESGLI) has also published guidance for managing Legionella during the coronavirus outbreak that you may find useful.

The Chartered Institute of Environmental Health has published guidance on legionella risks during the lockdown and reopening safely (PDF)- Portable Document Format.

The government has also published guidance on managing school premises during the coronavirus outbreak (which includes controlling risks associated with Legionella).