WATER restrictions affecting more than 1.5 million people have been extended until well into next week as the crisis shows no sign of abating.
Dublin City Council engineers and international chemists still do not know what is crippling the capital's water supply.
And nightly shut-offs from 8pm to 7am that were due to end on Monday will last until at least Thursday and possibly longer.
The council said that while production has stabilised at the Ballymore Eustace water treatment plant – which supplies water for Dublin city and county as well as parts of counties Wicklow and Kildare – levels of treated water were still "well below" that required to meet demand.
The plant produces 480 million litres each day, but the region's daily requirement is 530 million.
Council officials said it was only through the implementation of nightly restrictions that it can address the shortfall.
One week into the crisis, engineers were still struggling yesterday to establish what caused the "characteristics" of the water to change.
Normally, when chemicals are added to the water they attract minuscule particles together to form a scum or cloud which leaves the remaining water safe to drink – but this has not been happening since last weekend.
The problem first arose around 10 days ago, but the council was able to rectify it. However, it re-emerged last weekend, and tests are currently under way to identify the cause. Restrictions will continue until the problem is resolved.
Tourism Minister Leo Varadkar said he was concerned about the impact of the nightly cut-off of water supplies on tourism and businesses.
He also criticised Dublin City Council's handling of the issue, saying it should be doing more to inform the public about what is happening.
"Obviously, anything that affects business and tourism, I am concerned about. I do think the city council could have done a better job in terms of communication. We know the problem is in Ballymore Eustace, but we don't know exactly what the problem is."
The council has apologised for the restrictions and asked customers to "bear with us".
"An analysis of the current situation carried out at Ballymore Eustace water treatment plant has shown a stabilisation in production at the plant," it said.
"However, despite this stabilisation, production at the plant is still at a level well below that required to meet demand. Coupled with this, storage levels at our treated water reservoirs remain at an unsustainably low level."
It stressed that there is no problem with the quality of treated drinking water or with storage levels of untreated water.
"A series of tests currently being conducted at Ballymore Eustace involves adjusting the various inputs to the treatment process, with the objective of identifying what caused the slowdown in production and how to resolve the issue," it said.
"Dublin City Council engineers and our central laboratory technicians continue to work 24 hours a day to identify the cause of the problem and to mitigate the effects."
The council conceded that "it may take some time to completely resolve the issue".
Meanwhile, work to install water meters at Littlepace in west Dublin had to be temporarily suspended following a protest by anti-austerity activists.
A spokeswoman for Irish Water said there was a "brief cessation of work for five to 10 minutes due to health and safety concerns that the 25 protesters were too close to the barriers around the area where meters were being installed".