More than 7,000 households experienced disruption to their water supplies over a 24 hour period as a result of a damaged valve.
Many United Utilities customers had their supply turned off overnight on Thursday so that the repairs could be carried out.
The areas affected include Hoghton, Brindle, Gregson Lane and Clayton Brook.
The company also warned users that they may notice low pressure or discoloured water after supplies were restored.
United Utilities said engineers had been working around the clock since Wednesday evening to repair the large valve at Hoghton which controls water supplies into the area.
Engineers routed water through other pipes in the network to keep supplies on tap and used storage capacity in Chorley’s underground service reservoirs.
Temporary water tanks were set up in other parts of Chorley in case the problems persisted.
Steve Williams, of Smithy Close, Brindle, said: “We noticed very low pressure and discoloured tap water from lunchtime.
“The problem got worse to the point that the toilet wasn’t filling and then the taps ran dry.
“It was a major failure, something affecting significantly more than 10,000 users.”
Derek Clarke, area water manager at United Utilities, said: “We’re very sorry for any inconvenience that this may have caused customers in the Chorley area.
“If people notice the water is discoloured, they should turn on the first incoming cold tap — the one closest to the stop tap, and run it constantly at a trickle.”