Dual-pipe reticulation for non-potable water: a survey of public health risks and their mitigation

Dual pipe reticulation schemes which supply non-potable water for domestic purposes can reduce potable water demand and make a contribution to achieving a supply-demand balance. Such schemes are not without their risks and this contribution outlines the public health risks associated with dual pipe distribution infrastructure. The first survey of its kind, the paper draws together material from a variety of published sources to present evidence from a wide range of jurisdictions to illustrate the risks, and assembles a suite of risk mitigation actions which can be used to improve the safety of such schemes. We find that three types of risk dominate the reported incidents and are particularly challenging to manage; cross-connections due to faulty installation or post-commissioning householder DIY projects, cross-contamination as a result of factors other than a cross-connection, and the deliberate or inadvertent misuse of a non-potable supply.