NI hosepipe ban remains in place
NI Water says demand is still 30% above normal and some areas have already suffered from a loss in supply.
The first hosepipe ban to be ordered here in 23 years remains in place.
After a week of sunny weather and very little rain, NI Water has said it cannot treat water quickly enough to satisfy the demand.
A number of homes in Lurgan, Co Armagh and Coalisland, Co Tyrone as well as some other areas - particularly those that are isolated and high lying, have experienced lower pressure and supply failures.
On Sunday evening, NI Water said demand is still 30% higher than normal, and re-issued its appeal to the public to reduce their usage.
Chief Executive Sara Venning thanked some local businesses who lent NI Water their tankers over the weekend to help their efforts to meet demand.
"We would like to thank all our customers who are working with us to limit their water usage,'' she said.
`"However, demand remains much higher than normal, particularly during peak times, so we are still struggling to get water around the system quickly enough.
"By helping us, you are in fact helping yourself, as the ultimate penalty for using water unnecessarily is not a fine it is the heightened risk of widespread supply interruptions.
"We continue to maximise our water production and I am grateful to our dedicated workforce who are working continuously day and night to ensure we keep customers in supply. We have also been aided by a wonderful response from business who have supplied tankers to augment our own fleet enabling us to service reservoirs most at risk.''
The hosepipe ban applies to domestic customers.
NI Water said business customers have not been affected because they reply on water use for their livelihood and may already have water efficient systems in place such as metering or water recycling systems.
The last summer hosepipe ban in Northern Ireland was ordered in 1995.
Warm weather is set to continue this week, with temperatures up to 27 degrees forecast in Northern Ireland.