NI Water dispute closes primary schools
More than 1,000 primary school pupils spent the day at home, as the NI Water industrial action continues to disrupt supplies.
Water supply was restored to about 4,550 properties in County Tyrone late on Tuesday.
However, about 3,200 properties in West Tyrone and Fermanagh remain cut off.
Regional Development Minister Danny Kennedy said talks between unions and management must continue until "this is thrashed out and resolved".
He was speaking in the Northern Ireland Assembly after earlier taking part in talks at the Labour Relations Agency in an attempt to resolve the dispute over pensions.
Talks were continuing late on Tuesday night.
Last month, Nipsa, Unite and GMB members voted for a work-to-rule and withdrawal of on-call services and overtime.
However, an agreement was reached just before Christmas between NI Water and trade unions which meant people would not be without water supply for more than 24 hours.
Mr Kennedy said if there was no resolution of the dispute, the emergency protocol that was in place over Christmas must be re-instated.
"This would give the public protection of services and parties time and space to conclude on outstanding issues," he said.
Stormont's regional development committee has called an emergency meeting for Wednesday morning.
Analysis: Why the west?
NI Water says the problems are concentrated in the west of Northern Ireland because the infrastructure and equipment there is mainly older.
Sites in the east have been more recently refurbished.
NI Water says it is not principally down to the 'Project Alpha factor'.
Project Alpha is a 25-year Public Private Partnership (PPP) contract to upgrade and operate four water treatment works.
Speaking ahead of the latest round of negotiations on Tuesday, NI Water chief executive Sarah Venning said she understood the anger of customers who had their supplies interrupted.
"We're here today, absolutely determined to find a resolution to this dispute," she said.
"We're willing to listen to any reasonable offer, but we've been given a very clear remit to find a resolution within executive pay policy."
Ryan McKinney of the union, Nipsa, said they were prepared to stay as "long as it takes", adding that workers had "every right to defend their pensions".
"We're not going to be pushed into a settlement that doesn't benefit our members," he said.
"They fear that they are going to lose out in the long term. Pensions is a long-term commitment and we have to reach the right settlement for those people."
On Monday night, 9,000 customers were without water in west Tyrone and parts of counties Derry and Fermanagh.
The company has a postcode search on its website for customers to check for the latest information on supply disruption in their areas.