Backflow Contamination of Mains Water Supply

13. (1991):

A recent investigation of a contaminated drinking water problem by Buildings & Grounds, identified backflow of contaminated water into the mains water system as a likely cause of the problem. Part of the report from Mr Bruce Bailey, Superintendent, works & Services, reads as follows:

"The backflow problem is rife across Campus in the laboratories. To explain this, in a laboratory sink we often find a tube (either plastic or rubber) fitted to a tap over the sink and lying loose on the bottom of the sink. Whilst the tap with the tube on it is under pressure there is no problem. Once the water in the area is shut down, with this tap left on and another tap opened at a lower level than the open tap, gravity takes over and a backflow in the pipework occurs. Should there be bacteria in the sink where the tube is lying, when a backflow occurs with the tap open there is a very strong possibility that the bacteria will be drawn into the pipework."

One of the pillars of an urban society is a potable, uncontaminated water supply. It is essential that every effort be made to eliminate any possibility of backflow from sinks by ensuring that flexible hoses are short enough to be above sink level, or if longer (e.g. a safety shower rose connected to a sink tap) by ensuring that appropriate fittings and supervision are provided to ensure the hose outlet is hooked above sink level when not in use.

It is recommended that each Area management organise their staff to inspect all sinks in their Area as soon as practicable, and that this safety item be included on the routine audit checklist for each Area.

For further information contact:
OHS Officer, e-mail: OHS.Officer@anu.edu.au