Findings from the DWI Report on Dual Pipe Water Recycling Systems and Risks to Water Quality

Findings from the DWI Report on Dual Pipe Water Recycling Systems and Risks to Water Quality

15th April 2024 news 0


The UK Drinking Water Inspectorate has recently released a report by WRE member Cranfield University on ‘Dual Pipe Water Recycling Systems and Risks to Water Quality’. The report was authored by Prof Paul Jeffrey and WRE Secretary, Dr Kristell Le Corre Pidou from Cranfield University, in collaboration with colleagues from Royal HaskoningDHV – Peter Kuin, Gerard van Houwelingen and Sheryll de Valk. The aim of the research underpinning the report was to review the risks associated with dual pipe systems for water recycling and to assess the suitability of English and Welsh regulations to manage the risks from evolving systems.

Through reviews of the academic and grey literature, existing regulatory tools, standards, and guidance, the research team sought answers to six specific questions:

1. What are the risks from dual pipe water recycling systems and how are these best controlled?

2. Do the risks vary depending on the age of the systems? Are the risks of cross- connections suitably mitigated in the short and long term?

3. What are the regulatory controls for these types of systems and are they adequate to mitigate risk?

4. What is the user/ owner perception of such systems?

5. How sustainable are such systems as a whole life cost?

6. What are the barriers to dual pipe recycling systems and whole life benefits vs other recycling options?

The research found that although there exists a suite of regulations and standards to alleviate the risks of cross-connections in household settings during installation, there are fewer safeguards to control the risks of cross-connection due to post-installation plumbing modifications. Similarly, there are opportunities to improve risk reduction measures and improve public understanding of dual pipe systems to deter the inappropriate uses of this lower quality water. The research also found that many dual pipe schemes in the UK have either been mothballed or have never become operational. The reasons for this are unclear, but international experience suggests cost, maintenance, and inconsistent public support for recycling are factors.

Based on the outcomes of their investigation, the research team suggest a number of actions in order to better control the risks from dual pipe systems and emphasise that policy initiatives which revise and / or augment existing regulations and standards in this area should assess which actions meaningfully underpin the protection of human health. Policy makers and regulators are also urged to look to early adopters of such systems (e.g. Australia and the USA) to benefit from their experience and knowledge. Three of the suggested actions are central to the future expansion of dual pipe systems (and in some ways other forms of water recycling schemes) in England and Wales.

The authors call for a review of the risk mitigation measures across regulations and standards to separate provisions for drinking water supplies from those for other uses. This would provide a more coherent governance framework for dual pipe supplies. Secondly, they advocate the inclusion in the regulatory and standards framework of a wider variety of types of dual pipe schemes (in terms of both source water and end uses) and say that the targets for water quality are set based on the intended use. Thirdly, they recommend the provision of a ‘single source’ of updated guidance for scheme designers, installers, and operators on applicable regulations and standards.

The Inspectorate is currently working with Defra to understand the implications of this research.

The full report can be accessed at:

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