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Drinking water quality

Information and Guidance on water quality for businesses reopening following lockdown created by Covid-19

The restrictions placed on businesses and people by UK governments as a measure to restrict the spread of coronavirus in mid-March 2020 left many premises having to close suddenly. As a result, many drinking water systems may have become stagnant over this period and thus the risk of potential water quality issues.  

Guidance for building owners, landlords and managers and to those who operate Water or Refill Fountains on how to restore their drinking water systems on reopening


As a result of the closure or part closure of buildings, drinking water systems may have been subject to stagnation due to a low turnover of mains water or water in storage. This could have resulted in water in internal plumbing systems warming up, microbiological regrowth or an increased uptake of plumbing metals. Unless steps are taken before the building is reoccupied there is a risk of adverse drinking water quality and potential risks to health.

How to prevent this

NI Water continues to maintain its networks and systems to assure the quality of water entering a building. For building owners, manager and landlords it is critical that they also take action to manage the risk of water systems that have not been used, to ensure that as staff return, water systems are safe. In the first instance there are some simple steps that can be taken to recommission your drinking water system:

  1. To ensure that the water in the plumbing systems is fresh, run all taps individually, starting with the tap nearest to where the water enters the building and moving systematically to the most distant outlet. It should be sufficient to run until the water is clear and feels cool to the touch. Building owners should also be mindful of the risks to all non-drinking water systems as well such as heating systems.
  2. Where water is supplied from storage, storage cisterns should be emptied and filled with water direct from the incoming supply, before the taps are flushed; flushing should be carried out in a manner which minimises aerosol generation. For example, removing shower heads prior to flushing, to reduce the risks of Legionella transmission.
  3. Safety considerations should be made for those flushing including appropriate Personal Protective Equipment (PPE); ensure that all appliances are also thoroughly flushed through before use, using manufacturer’s instruction manual. If the property has any internal filters or water softeners, these should be checked to ensure they are working correctly as outlined in the manufacturer’s instruction manual;
  4. Ensure that if plumbers are required to make any changes or repairs to the plumbing system that only approved plumbers under the WaterSafe scheme are used
  5. For larger buildings, those with tanks, showers, water heaters and more complex pipework the expectation is likely to be for more extensive flushing followed by cleaning and disinfection. If you have a complex plumbing system you should ensure you have a competent person to oversee this work.


Further information

NI Water Response to Covid-19

Drinking Water Inspectorate NI (DWI NI)

Water UK / WRAS “Looking after water in your home

WaterSafe approved

Water Supply (Water Fittings) Regulations (Northern Ireland) 2009

DWI - Guidance On Maintaining Drinking Water Quality When Reinstating Water Supplies Following Temporary Closure

Water UK / WRAS “Looking after water in your home” -

Q&A for drinking water from DAERA website

Key advice and guidance can be found from the following Regulators and Government bodies:


WaterSafe approved


BS 8580-1:2019 Water quality. Risk assessments for Legionella control. Code of practice

BS EN 806-2:2005 Specifications for installations inside buildings conveying water for human consumption.

Design: PD 855468:2015 Guide to the flushing and disinfection of services supplying water for domestic use within buildings and their curtilages

Legionella Control Association

Legionnaires' disease is a type of pneumonia caused by bacteria. You usually get it by breathing in mist from water that contains the bacteria. The mist may come from hot tubs, showers, or air-conditioning units for large buildings. Further information on Legionnaire’s disease can be found at the following links:


Awareness / interest


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