Covid-19 - Recommissioning Water Systems

Buildings that are temporarily shut down (mothballed) should follow the guidance in HSG 274 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 that the water system has been taken out of use
4. Have a plan in place for recommissioning the water system

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.  

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.   Follow up samples may need to be considered as part of the recommissioning plan.

Please contact your Account Manager if you wish to discuss implementing recommissioning plan for after restrictions are lifted and your building is ready to be opened.