Uisce Éireann says crews are continuing to repair a major burst on a trunk water main affecting around 2,000 customers across Inishowen.
The utility had expected repairs to be completed by 3pm, but that has now been pushed back until 8pm because of the complexity of the work.
It says crews encountered difficulties locating the exact point of the burst, contributing to the delay.
Uisce Éireann is reminding customers that, even after repairs are completed, it may take between two and three hours for normal water supplies to return.
Customers on higher ground and at the end of the network may experience longer delays.
