About 1,500 properties were left without water overnight after a water main burst.
The burst happened in Glasgow Road, Kilmarnock, on Saturday.
Scottish Water said its engineers had worked through the night to repair the 16in main.
The company apologised for the inconvenience and warned that as supplies were restored, properties could have discoloured water which would eventually run clear.
A spokesman said: "The repair proved to be complex and we would like to thank customers for their patience while we continue to resolve the situation.
"We apologise to anyone who has been without water during the period of this incident and would like to assure you that we are doing all that we can to ensure supplies are restored."