The disruption affected homes, schools and businesses in the Lurgan, Craigavon, Kilmore and Portadown areas.

A spokesman for the Water Service said the vast majority of people have now been re-connected but that there may be some isolated cases of airlocks in the system.

However, the decision to cut off supplies while essential repairs were carried out in the area, prompted an angry reaction from headmasters and local politicians.

Faulty control valve

It was ordered following the discovery near Portadown of a faulty control valve on the mains network.

Dozens of schools in the Southern Education Board area had to close and a number of businesses in County Armagh area were affected.

One school principal said that she had only been informed at 3.35 on Wednesday afternoon.

"I phoned around to other schools and they had got the message at the same time, one school got a fax at 3.45, the pupils were all away home," said Joan Aldridge, the principal of St Mary's primary school at Derrytrasna.

"I was very angry to get a call so late especially when I was told by neighbours when I got home that a van went around at 2.30 - why couldn't schools have been informed at that stage?"

Dolores Kelly: Critical of poor communication about supply problem

Craigavon mayor Dolores Kelly said lessons should have been learned from previous emergencies such as the recent storms.

"This sort of crisis should have been handled much more effectively and the message communicated," she said.

However, the role of the Water Service was defended by senior engineer David Dodds who stressed that supplies were cut off due to an "emergency situation".

He said that a fault was discovered on Sunday evening but a decision to cut off the supply to allow repairs could not be taken until the valve arrived on site.