Water management considerations during the lockdown period  [COVID-19 precautions]

[Updated 09/04/2021]

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Regulations & Guidance 

A reminder the following Acts, Regulations and Guidance documents still apply to organisations during the COVID-19 lockdown.

However, during this time, there are many hazardous situations that have the potential to occur within buildings and their water systems [i.e. stagnation, poor turnover, poor temperature control and increased levels of contamination].  These situations may then go on to cause outbreaks of Legionnaires’ disease.  Duty holders must therefore be taking all reasonably practicable precautions to control the risks from Legionella and other associated water safety during this time.

What are the minimum standards to be achieved…

  • Water systems supplying ‘critical systems’ such as hospitals are expected to be maintained as usual during this time [in accordance with S/HTM 04-01];
  • Evaporative cooling systems are expected to be maintained as usual during this time or switched off safely [in accordance with HSG274 part 1].

What other controls should you consider…

  • Hot and cold-water distribution systems within buildings that are either unoccupied and / or under occupied shall be ‘suitably managed’ to mitigate stagnation and associated contamination with waterborne bacteria.  Action to consider:
    • Do not drain tanks or pipework during this time – this action can cause issues with systems drying out and damage to the fabric of the system;
    • Ambient heat gain from a hot water system in an unoccupied and / or under occupied building, irrespective of flushing regimes, will encourage bacterial growth within distribution systems.  As such turn off the calorifier or domestic water generator [open the drain at the base to purge any sediment that may have built up, allow the water to flow until it runs clear, close drain valve];
    • Consider reduction in the volume of water stored i.e. reduced capacity of water tanks in the building; taking care with sectional tanks not to lower below horizontal seals to prevent drying out;
    • Undertake hygiene flushing of outlets throughout the building [multiple times a week] in order simulate occupation of the building and prevent stagnation;
    • Consider the use of point of use filters as a short-term control during this time;
    • When monitoring water system temperatures [in accordance with HSG274 part 2], a sustained loss of control will still require Legionella sampling until control is gained.

  • During lockdown buildings will become unoccupied and their water systems shall be left charged with water [known as 'Mothballing'], thus circumventing the risks/issues associated with draining down/drying out a water system. However, Legionella risk will need to be suitably managed in accordance with HSG274 Part 2 paragraphs 2.50-2.52 (including recommissioning before reoccupation).
    • Ensure signage is placed at entrances to those unoccupied buildings / areas that are ‘mothballed’, detailing the area is not in use and shouldn’t be accessed for use;
    • Remove shower heads & hoses, spray inserts or tap diffusers to minimise biofilm formation when not in use;
    • Consider dosing the system with a residual disinfectant [i.e. Hydrogen Peroxide / Silver Peroxide this is a specialist activity and should only be completed by a competent person / appointed contractor);
    • A recommissioning plan should be drafted and ready for use [see below].

What to do when lockdown is lifted…

DO NOT put a building or system back into immediate use.  Individuals who reoccupy these buildings and start using water systems that have been stagnant for a period of time may be exposed to legionella [and other waterborne pathogens]. 

The recommissioning plans:
    • Identify those buildings to be re-opened and when.  Recommissioning of those buildings needs to be planned given the availability of maintenance contractors to assist with the recommissioning work on the water systems and capacity of microbiological testing laboratories to process legionella samples.  
    • There will be financial costs and / or other resource issues as part of the recommissioning process.
    • WSP Part 4.1.2 Control Measures - Hot & Cold Water Systems.  This document was issued to clients on the 09/10/2020 as part of technical service update.  This specific part of the WSP includes a detailed plan to be followed for management of water systems and their recommissioning following a period of being unoccupied [see section '4.2 Procedure in the Event of Closure of Part or All of a Building’ and the associated table with guidance'.  Broad summary being:
    • Evaporative cooling systems – existing procedures should exist for starting up and shutting down – these will need to be followed.

Guidance from other Bodies and Agencies








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