(SD 3423) Draft Final Report to the Department of the Environment
Report No DWI0445

Apr 1993


Backflow can occur from a customer's premises with two effects; causing contamination of the mains network and localised contamination. A study of such events form the subject of this report. There is an apparent lack of information concerning the frequency, cause and consequence of backflow events from customer's premises.

A feasibility study was therefore undertaken to determine the practicability of carrying out a major study of backflow in water distribution systems. A questionnaire was sent to all water undertakers asking for information on proven and tentative backflow events. This was followed by visits to those who had reported proven events, so that further information could be obtained.

The level of return for the questionnaire was very high (93.5%). A total of 78 proven events were reported for the last 10-15 years divided between 22 water undertakers. The majority of backflow incidents have occurred at industrial business premises and are therefore relatively serious. However, the recent increase in industrial inspections should help to reduce the likelihood of backflow events in the future. There is discussion within this report as to how the protection given by the existing legal framework to inhabitants can be made more widely known and hence adhered to. This framework appears to be adequate in that both the byelaws and the 1991 Water Industry Act detail the responsibilities of the owner occupier with regard to purchase and use of apparatus to avoid backflow.

The data gathered in this feasibility study indicate that a further, more extensive study of backflow events is not required.

Copies of this report may be available as an Acrobat pdf download under the 'Find Completed Research' heading on the DWI website.