The Oireachtas committee on water will not complete its work on time after the Dáil voted to allow it to continue meeting for another four weeks.
The committee, which is examining how to best fund domestic water services, has agreed that the network should remain in public ownership subject to a referendum, but remains divided on a number of issues including how the €5.5bn needed to upgrade the network will be sourced and if there should be a charge for excessive usage.
While charges are expected to be scrapped, one issue being debated includes striking a legal agreement between the State and Irish Water where some €240m a year which was expected to be collected in charges will be paid to the utility each year.
This would allow the company to borrow money on the international markets to fund upgrades, as it would be able to prove it had a guaranteed revenue stream.
The committee has also sought legal advice on how best to comply with EU law over the 'polluter pays' principle. It has been suggested that each household be given an allowance of water, with a charge to be imposed if this threshold is breached, but Sinn Féin, Fianna Fáil and anti-water charge groups are opposed.
The committee will also have to decide what constitutes excessive usage.
"One question to be addressed is what is a polluter?" one source said. "It's not defined in legislation. How can they be identified?"
Sinn Féin's Eoin Ó Broin said that imposition of an excessive usage charge could end up generating small amounts of money, for a large upfront cost.
"The real issue is the costs," he said. "We know 56pc or 58pc of households have been metered, and it may cost €300m to complete the metering programme. It would cost around €20m a year to monitor usage through the billing system."
The committee resumes on the week of March 20, and must report to the Dáil by April 14.