Hundreds of households in St Austell were left without clean drinking water this morning.
South West Water said it had received more than 300 calls from residents in St Austell and Bugle who woke to find dark brown water coming out of their taps.
In a statement the firm said sediment had entered the water supply following maintenance in the area.
The statement said: “South West Water apologises to customers in the St Austell area who have been experiencing discolouration to their water supply.
“In order to carry out essential maintenance on the network we needed to change the way water flows around the system. This unfortunately resulted in some sediment being disturbed due to changes in flow and pressure in the pipes.”
The firm said all affected customers had been contacted and the problem has now been resolved in most areas.
The statement continued: “We contacted customers in the area by text message last night, advising them to run their kitchen taps, and worked overnight to flush the distribution network.
“We continue to carefully monitor the situation and for the majority of customers supplies are now back to normal. We are working in a few isolated areas where supplies may still be affected.”