Advice for those with Water System Responsibilities under the current COVID-19 Pandemic

Update: 26 march 2020

We have been in contact with the LCA and HSE regarding what the expectation is for management of water systems during this period of COVID-19 precautions.  The Health and Safety at Work Act still applies and Dutyholders must be taking reasonably practicable steps to control risk from legionella throughout this time.  Dutyholders implicated in an outbreak of Legionnaires’ disease resulting from actions taken for COVID-19 precautions are not likely to have any exemption from prosecution.

While we cannot make sweeping statements about what is critical, what can be deferred for a few weeks and what can be deferred for longer.  The legal responsibility for legionella control lies with the Dutyholder, but we will be providing expert advice to our customers to assist them in compliance.  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:

  • If the building is still partially in use take additional measures to keep the remaining occupants safe:
    • If possible, drop stored water levels in tanks to maintain <24 hours storage
    • Flush to simulate use – weekly flushing may not be sufficient
    • Monitor temperature to ensure thermal gain in cold water is controlled
    • 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
    • If controls are lost (temperature, biocide levels, etc.) the guidance in HSG274 is to sample for legionella weekly
    • Consider other short term measures to keep remaining occupants safe such as point of use filters at designated locations with other areas shut off


  • Buildings that are temporarily shut down (mothballed) should follow the guidance in HSG274 Part 2 paragraphs 2.50-2.52:
    • Do not drain down pipework
    • If possible, remove sources of heat and external thermal gain
    • Lock off, place signage on doors and otherwise advise potential users that the system has been taken out of use
    • 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 working 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.  Be aware of this, make your customers and supply chain aware and manage expectations accordingly.

There is potential for multiple outbreaks of Legionnaires’ disease following the COVID-19 outbreak if actions taken now are not carefully considered.  Please be aware of this, and that the responsibility for legionella control lies with the Dutyholder.

Information correct as of 26 March 2020


We would like to inform all our clients that we are taking the COVID-19 pandemic extremely seriously and the health, safety and wellbeing of our clients and employees is of the utmost importance.

As a Water Undertaker we are in regular contact with the Government and we are also following industry guidelines.

Whilst the immediate focus is on the prevention of the spread of COVID-19, it is important to remember that the Health and Safety at Work Act 1974 is still in place.

With regard to water use:

“an employer or those in control of premises must continue to manage any risks arising from their activity and this includes legionella control.”

Legionella bacteria still poses a risk to water system users. In order to demonstrate control of the risks from the water systems, it is useful to be creative in the way control measures are undertaken. It is important to remember that many of the control measures are that of monitoring as opposed to direct interventions.

To prevent the Corona virus from spreading we must all minimise day to day contact. In domestic environments, to protect both employees and clients alike it is vital that any information on those that are self-isolating is made aware to us before the visit. Our employees will confirm in person at the time of appointment on the health status of the site contact whilst maintaining a 2 metre distance. All employees are equipped with sanitiser and wipes and will continue with stringent hand washing whilst keeping the work tasks as short as possible. We are in daily contact with our employees to ensure they are not showing any symptoms.

We will encourage, where possible, the taking of water temperatures from plant/tank rooms and unoccupied areas such as laundries and first aid rooms to further reduce person to person contact.

Some tasks such as lower-risk Legionella risk assessments could be put on hold until the current situation improves.

A key control measure in Legionella control is that of turnover, this is not always possible if buildings are shut down. Remember in non-healthcare premises, all outlets must be used as a minimum once per week. If they are not, then a simple intervention such as a planned flushing programme should be put in place. If this is not possible, it is crucial to follow the correct mothballing procedures.

If all outlets have not been flushed weekly, then they should be treated like a new system i.e. flushed and disinfected before being brought back into use. For specific guidance please consult HSE advice document HSG 274 Part 2. If water use has significantly changed then consideration should be given to reviewing and updating the current risk assessment.

It is also vital to continue to monitor chemical control measures such as Chlorine Dioxide and keep chemical levels topped up.

We will work with our clients and offer as much support as possible during this difficult time. Please use 0800 028 3557 then Option 3 if you have any questions.

We will constantly reviewing any changes/updates from the government, HSE and LCA and will update this blog with the information.

Information correct as of 25 March 2020

Stay Safe
Total Water Solutions Team