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Detecting Cross Connections

February 24, 2011

The introduction of third pipe systems has accompanying risks of cross connections. Rapid detection of cross connections is vital for public confidence and acceptance.

Recycled Water

Project 3001 - Detection of cross connections in potable water distribution systems – Stage 2: Field trials of candidate detection parameters (CSIRO)


Cross-connections between reticulated recycled water and the potable water supply are a potential risk that accompanies the introduction of third pipe systems. The capacity to rapidly detect cross connections is highly desirable to ensure public confidence and acceptance of these schemes. Initially, a series of laboratory studies was undertaken to evaluate the ability of a range of parameters to detect at least 10% contamination of recycled water in the potable water supply. The data generated demonstrated that electrical conductivity, fluorescence and ultraviolet radiation were all effective parameters at the 95% confidence level. The first stage of this project was completed in 2009, and this report is now available through WQRA.


A key outcome of the initial cross connections work was to prepare a shortlist of promising techniques, which could be examined in a more extensive field trial. The Stage 2 field trial work is now underway, with a range of candidate parameters shortlisted from the initial work being measured online at the Hunt Club estate in Melbourne and at Rouse Hill in Sydney to determine diurnal and weekly variations in water quality that may arise from >10% cross connections in dual pipe systems.

The Hunt Club trial has now been completed, with the field trial at Rouse Hill currently underway. Although there is still significant data analysis to occur, both electrical conductivity and fluorescence techniques have demonstrated consistently measurable differences between the potable and recycled water supplies in the Hunt Club trial. The full project report, which will be available in July 2010, contains the detailed analysis of both the Hunt Club and Rouse Hill field trials. This work has been funded by Melbourne Water, SEWL, YVW, CWW and Sydney Water.