United Utilities has admitted a charge in relation to the cryptosporidium outbreak scandal that hit Lancashire's water supply in 2015.
The major firm appeared before Preston Magistrates’ Court in a prosecution brought by the Drinking Water Inspectorate.
Hundreds of thousands of homes in the county were left without safe drinking water when traces of cryptosporidium were found in summer 2015.
The company pleaded guilty to supplying water to premises from the Franklaw Water Treatment Works at Catterall, Garstang, that was unfit for human consumption between July 30 and August 18, 2015.
Two further charges of failing to disinfect water used for domestic purposes, and failing to design and continuously operate an adequate treatment process were withdrawn.
Prosecuting, Richard Bannell said: " This is in effect the first hearing of the case. I'm glad to say that time has enabled matters to be progressed.
"This case raises out of 700,000 consumers in north Lancashire. We are dealing with the impact on consumers that followed from that event."
Defending, Lisa Roberts QC entered the plea on behalf of the firm.
District Judge Jane Goodwin committed the case to Preston Crown Court for sentence on August 21.
After the case, the firm issued a statement which said: “United Utilities has pleaded guilty to one single charge of providing water that was unfit for human consumption between 30 July 2015 and 18 August 2015, from our Franklaw Water Treatment Works, Preston.
"The charge was brought by the Drinking Water Inspectorate (DWI) under the Water Industry Act 1991.
“We have taken a full and open role with the DWI during its investigation, and complied with all its requests for information. A full programme of remedial and repair work has already been implemented to safeguard future supplies.
“We will not be making any further comment until after sentencing, later this year.”