Thousands of householders and businesses in the Republic of Ireland are still without water on Monday due to a burst water main affecting parts of County Louth and County Meath.
Irish Water has said it will be Thursday before water supply is restored to 50,000 homes and businesses.
The burst happened on Friday morning.
"Storage reservoir levels are now critically depleted," Irish Water said.
It said works to repair the water main have been more difficult than first anticipated.
This is due to the age and type of pipe, as well as the "complexity of the repair".
It said the water main that supplies the Staleen Water Treatment Plant is located over four metres underground.
"The pipe is 50-years-old and has warped," Irish Water said in a statement.
"In addition it is one of the highest pressure pipes which makes the repair more complex.
"A bespoke solution is now being engineered. We expect normal supply to be restored on Thursday."
The plant supplies drinking water to Drogheda and its surrounding areas, as well as parts of south Louth and east Meath.
Irish Water said that in order to manage the remaining water resource it had re-commenced rationing water for some parts of Drogheda at 08:00 local time on Monday.
It said that water tankers and containers had been mobilised from across the Republic of Ireland as well as from Northern Ireland Water.
"This water is being delivered directly into the water network to increase available water for the rotating water roster, whereby water is rationed to different areas in a planned way," a statement said.
"This should ensure that all locations have water for certain periods. The roster of locations will be posted on Louth County Council and Irish Water web sites and will be updated."
Temporary water stations have been set up at various locations across east Meath and Louth.
Consumers have been asked to bring clean containers and to boil water taken from these stations before use, as a precaution.
NI Water said it would "continue to liaise with colleagues in Irish Water and provide support until the incident is concluded".