DIY enthusiasts in Bath are being urged to take extra care when plumbing in new appliances to avoid water pollution incidents.

The warning comes after Wessex Water discovered seven properties in Bath and North East Somerset where equipment such as washing machines had been connected to the wrong part of the sewerage network in the last six months.

A range of kitchen appliances as well as some bathrooms and even toilets were found to be plumbed into drains that are designed to remove rainwater and which feed directly into streams and rivers.

The equipment should have been connected to the foul part of the sewerage system so soapy and dirty water can be properly treated at a sewage works before being released into the environment.

The Bath firm has set up Operation Streamclean to prevent pollution and work out the causes of incidents.

Streamclean co-ordinator Larry Spiers said: "Throughout the year we survey streams, rivers and drains in B&NES looking for signs of pollution. We are then often able to work our way along drains to trace where the pollution has come from and find it is sometimes from domestic properties.

"Fast-flowing water, particularly during winter months, increases the likelihood of pollution being carried downstream, putting more fish and plantlife at risk, so it's important that people take extra care to stop this problem at its source by connecting appliances correctly."

Wessex Water said it believed more people may be installing new bathrooms and kitchens themselves rather than using professionals to save money in the recession. A simple dye test to check whether an appliance is draining identifies offending properties.

Mr Spiers said: "Rivers that are miles away from a misconnected home can be affected by pollution. But by simply adding harmless dye to water drained from an appliance we can then trace how it travels through the system. Often homeowners are not aware of this pollution issue but most are environmentally-conscious and keen to put the problem right when we explain how the system works."

This year Wessex Water's Streamclean team has identified 319 misconnected appliances including 69 washing machines, 54 handwash basins, 54 toilets and 20 full property misconnections throughout its region which spans B&NES, Somerset, Bristol, Dorset, most of Wiltshire and parts of south Gloucestershire.

Anyone with concerns can contact Operation Streamclean by calling 0845 600 4 600.