Scottish Water has been fined £3250 after supplies to thousands of homes were found to be unfit for human consumption.
People living in Dalziel Park, New Stevenston, Carfin, Newarthill, Holytown, Mossend and Chapelhall woke up one morning in June 2015 to find the water coming from their taps appeared to contain an oily-based substance.
Householders were warned not to use water for anything other than flushing the toilet. More than 6000 homes were affected. People had to queue for bottled water at collection points and others had supplies delivered to their homes.
At Hamilton Sheriff Court this week, Scottish Water admitted supplying water contaminated with hydrocarbons, iron and manganese.
Sue Petch, Drinking Water Quality Regulator for Scotland, said: “This incident caused considerable inconvenience and worry to a large number of consumers.
“People’s confidence in the safety of the water supply was compromised and our investigation found deficiencies with Scottish Water’s operational processes.
“Scottish Water have worked to improve procedures and I look to them to rebuild public trust and ensure an incident of this nature never happens again.”
The court heard restrictions were in place from the evening of June 17 to the morning of June 19, forcing schools and businesses to be closed.
A probe showed the inadvertent shutdown of a water main during a planned repair resulted in dirty water from two sources in Newhouse Industrial Estate being drawn back into the supply system.
Health officials stressed there was “unlikely to have been a significant impact on the health of anyone consuming the water”.