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DIY risk hinders greywater reuse prospects

by Trevor Loveday

The risk of misuse by owners and operators is a major obstacle to growth in the use of dual pipe systems to enable households and businesses to reuse shower wastewater (greywater) according to a report by the Drinking Water Inspectorate (DWI).


In its review, the DWI said regulations and standards can ensure that installation of greywater reuse systems for toilet flushing and other non-potable purposes are safe for people and the environment. But “influence over householder behaviours (such as do-it-yourself work and use of recycled water) is much more challenging,” it warned.


The DWI conclusions include: “Current regulations and standards focus very strongly on the installation phase of dual pipe systems. This is partially understandable given the context within and time at which they were developed. As the sector matures however more attention should be given to the operational phase of dual pipe schemes.”


The chief risk, the report said, is from cross connection of grey water recycling piping and potable water plumbing. It reports how cross contamination has been seen in a number of countries where dual pipe systems have been trialled or established including Japan, Australia, the Netherlands, and the USA. 


The DWI cited in its report, how, in 2001, The Netherlands government banned all large-scale, dual-pipe installations in households “based upon concerns of possible misuse of the water and the unacceptable risk that it poses to public health.” That followed 200 people contracting gastroenteritis from norovirus infections as a result of a greywater dual supply system in a new housing estate being cross-connected.


The inspectorate report points to the Australian regulations on dual pipe installations as “arguably best-in-class internationally; affording clear and practical rules and advice for scheme designers, operators and users with a minimum of documents to consult.” Current UK regulation and standards, it said, are “dispersed… with requirements and advice spread across multiple documents.”


It goes on to say that while the UK has regulations and standards in place to offset the risks of cross-connections in household installation, “less evident are measures which might control the risks of cross-connection due to post-installation plumbing modifications”.

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