Thousands of homes are facing a weekend without water due to a burst pipe, although supplies are starting to return to some customers.
An estimated 40,000 homes are thought to have been affected by the incident in Dolgarrog, Conwy county on Wednesday, which forced some schools and businesses to close.
Welsh Water confirmed the pipe had been repaired on Friday afternoon but water would not be fully restored to for “up to 48 hours”.
The company’s chief executive Peter Perry described the incident as a “catastrophic failure” caused by ground movement, which could not have been foreseen or prevented.
Speaking to BBC Radio Wales Breakfast, Mr Perry said: “We’ve seen no increases in flow to indicate there was trouble until Wednesday when we saw this catastrophic failure.
“Conwy, Dolgarrog, Trefriw, Llanrwst, Eglwysbach and few others are now coming back into water.
“We are doing this as a controlled operation. The last thing we want now is to have further bursts on the system,” he added.
Welsh Water said supply would come back on at different times for different people and “discoloured water” was normal after a supply interruption.
The company said thousands of homes had been restored by Saturday morning.
Some in Conwy town said their water “dribbled” back on at about 04:00 GMT on Saturday morning.
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Eligible households will be paid £30 for every 12 hours their supplies have been affected while business customers will be paid £75 for every 12 hours, as well as being able to make additional claims for lost earnings online.
Bottled water stations have been set up at four stations in Conwy, running in Park Eirias in Colwyn, Zip World Conwy, Llandudno West Shore car park and Bodlondeb site.
Several schools, businesses and community hubs were forced to shut on Thursday and Friday due to the water outage.
The company said the damage to the pipe, which was in a river, had been caused by pressure from rocks.
The network is almost 900km (560 miles) long and includes 13 underground storage tanks, the largest of which is the size of nine Olympic-size swimming pools.