It could be early next week before all Northern Ireland customers cut off from water supplies are reconnected.
About 32,000 properties will be affected but the situation is improving in Belfast.
Trevor Haslett, director of engineering at Northern Ireland (NIW), said the situation in urban areas was improving.
The ministerial Executive is holding an emergency meeting. The Scottish Government has donated bottled water and the Westminster coalition says it is ready to help.
One property in the north of the region was gushing out enough water to cover 2,000-3,000 houses.
An extra 40 per cent of water is being put in every day to support dwindling reservoirs but much of this is disappearing in leakages.
Temperatures in Northern Ireland hit a pre-Christmas record of minus 18C and were followed by a dramatic thaw, causing thousands of burst pipes.
Laurence Mackenzie, chief executive of NIW, is facing calls from political rivals of Sinn Fein water minister Conor Murphy to resign.
"My focus at the minute is getting through this situation," he said. "I have been in here since the issue arose. I believe I am doing the best I can to keep the team together and keep focused."
