DWI sets out governance framework for rain and greywater reuse

(by Karma Loveday)

The Drinking Water Inspectorate (DWI) has published a set of recommendations from the expert group it convened in July 2025, which provides a framework of governance principles to underpin safe water reuse.

Specifically, the framework will allow the use of rainwater and greywater for specific applications where drinking water quality is not needed (such as toilet flushing or garden watering), whilst ensuring the drinking water supply is protected from cross contamination or backflow.

The recommendations concerned water reuse in domestic settings in England and Wales, including similar uses in industrial settings, new builds and retrofits to existing properties. However, the report noted that said the principles could apply equally to industrial water usage. 

The recommendations were: 

• Recommendation 1: Define the domestic uses suitable for non-drinking water.

  
  

• Recommendation 2: Establish a risk-based framework to underpin all water reuse systems, by adopting a water safety planning approach, comprising risk identification and risk management, with accompanying standards for design, installation and operation.

  
  

• Recommendation 3: Provide standards for the maintenance of reuse systems to safeguard performance over the operational lifetime, including performance verification and testing frequencies.

  
  

• Recommendation 4: Review and update primary and secondary legislation to enable adoption and effective regulation of dual pipe systems.

  
  

• Recommendation 5: Deliver effective implementation and enforcement of legislation governing dual pipe systems.

  
  

• Recommendation 6: Improve competency within the industry through training and mandatory accreditation of designers, installers, operators and maintainers of dual pipe water reuse systems.

  
  

• Recommendation 7: Revise and update the guidance to the industry into a single Approved Code of Practice on an official government website.

  
  

• Recommendation 8: Require and facilitate mandatory registration of installed systems.

  
  

• Recommendation 9: Raise public awareness of the dual pipe systems, including the water saving advantages and risks to public health (see below).

  
  

• Recommendation 10: Carry out further work to establish water quality standards for non-drinking water.

The expert group said it was not possible within the timeframe to recommend with confidence which water quality standards should apply to non-drinking water, and there were differences of opinion as to whether standards are necessary, with some views that it is for Government to decide on an acceptable risk.

The report went on to identify some next steps to implement the recommendations; further work to develop an Approved Code of Practice for rainwater harvesting and greywater reuse; and work to inform options for a single set of water quality standards for non-drinking water.

There are two main public health risks with supplies of non-drinking water: 

• Contamination of the wider drinking water supply network through inadequate backflow protection, cross connections and poor plumbing. 

• Potentially-harmful-to-health exposure to non-drinking water by the end user.