As the region thaws from the big freeze, thousands have been left for days without mains water due to burst pipes.
In a statement, NI Water said it hopes to recharge the network by transferring water between reservoirs. The plan means all areas will receive a limited amount of water, but will in turn lose water for a time.
"A number of our reservoirs are currently at low water levels and we are trying to rezone and recharge the water network," a statement from the company said.
"NI Water have to alternate supplies from some of our reservoirs therefore customers will experience a loss of water for a period of time, however it is anticipated that this interruption will only last a number of hours and water will be restored to customers in a timely manner."
It is expected that supplies will be returned to Lisburn, Antrim, Belfast, Crumlin, Templepatrick, Newtownabbey, Kilkeel, Hilltown, Newtownhamilton, Newry, Ballymena, Cookstown and Londonderry between 6pm and 8pm.
After that, households in Rathfriland towards Newry, Mullabawn, Castlewellan Town, Banbridge, south Armagh, Warrenpoint and Mayobridge can expect to be affected.
Meanwhile, Regional Development Minister Conor Murphy said NI Water has been "struggling" to cope with the ongoing crisis.
An unprecedented number of people have been phoning the emergency hotline, with 6,000 calls received by mid-day on Monday alone.
"They have been dealing with around six times the normal number of calls," Mr Murphy told UTV.
"I've spoken to the Chief Executive and they are bringing in more resources, and more will be added tomorrow. NI Water has struggled to cope, but they have an action plan on the ground."
Andersonstown councillor Tim Attwood said there has been a "total communications breakdown" between the company and its customers.
"I have taken numerous queries and complaints this morning about the loss of water supply to parts of west Belfast," Mr Attwood said.
"People are angry that there has been a total communication breakdown from NI Water. Residents have spent hours on the phone to NI Water without getting connected. I have spent 3 hours, this morning, trying to get information from NI Water but their lines have been engaged. The NI Water website only provides limited information."
Bottled water has been handed out to customers left without water for over 24 hours at depots across the country, but the service has been criticised by some.
Customers outside the Westland House station in north Belfast - which has been serving all of Belfast - said supplies ran out early on Tuesday morning.
"There's none there," one couple told UTV. "It's not a bit fair. We called the helpline but it takes you nearly an hour to get through, then they just say there's nothing they can do."
Another man said: "We've come up to get a supply only to be told it's run out. It's a long way to come over from south Belfast."
Drinking water is to be made available from three drinking tankers in the city from 8pm to 10pm, at Avoniel Leisure Centre (east), Whiterock Leisure Centre (west) and Olympia Leisure Centre (south).
The City Council says customers are allowed 20 litres per household and are told they must bring their own containers. Shower facilities will also be provided at the venues.
Bottled water depot locations (28/12/10)
For customers currently experiencing a loss of water supply for more than 24 hours, bottled water will be available from 10am - 6pm at the following locations.
LONDONDERRY:
Northern Ireland Water Depot,
1A Belt Road,
Altnagelvin,
BT47 2LL
SEAGOE:
Northern Ireland Water Depot,
Unit 41,
Seagoe Industrial Estate,
Craigavon,
Co Armagh,
BT63 5QE.
BELFAST:
Westland House,
Old Westland Road,
Belfast,
BT14 6TE
OMAGH:
Northern Ireland Water Depot,
69 Gortin Road,
Omagh,
BT79 7HD
CASTLEDERG:
Castlederg Enterprise Centre,
Junction of Drumquin Road & Castlegore Road.
ENNISKILLEN:
Northern Ireland Depot,
Erne House,
Killyhevlin
BALLYMENA:
Ballykeel Depot,
Larne Rd.,
BAllymena,
BT42 3HA
STRABANE:
Strabane WwTW,
Park Rd.,
Strabane
ROSSLEA:
Derrygannon Community Hall,
Eshnadarragh,
Roslea.
ROSTREVOR:
Entrance to Cherry Hill,
Rostrevor.
COALISLAND:
The Civic Centre,
Coalisland,
Co.Tyrone
BANBRIDGE:
NIW Depot,
Huntley Rd.,
Banbridge.
PURDYSBURN:
Purdysburn Service Reservoir,
Alderwood Hill,
Ballydollaghan.