There will be no penalties imposed on those who fail to meet this week’s “deadline” for registration with Irish Water although some who fail to sign up for the new regime may face higher charges at some future point.

Irish Water spokeswoman Elizabeth Arnett said there will be an assumption made that those who do not confirm their details with Irish Water are part of a two-adult household so will face the standard charge of €260.

She also said that households who do not register with the controversial utility will not be in a position to apply to the Department of Social Protection for the €100 Water Conservation Grant although the deadline for applying for that grant is still some way off.

“We will make an assumption that you are on a standard charge, in other words that you have more than two adults in the household and that you have both water and waste water services, and in that respect your bill would be €260,” she told RTE’s Sean O’Rourke.

“You may need to have a lower charge than that, we can’t determine that unless you’ve contacted us and similarly in terms of the €100 conservation grant unless your details have been confirmed with us you won’t be able to apply to the Department of Social Protection for that grant”.

All told 30,000 households registered with Irish Water over the weekend. Just over half of the households expected to pay bills to Irish Water have registered their details with the new utility as a deadline of midnight tonight looms for registration to ensure accurate water bills.

Almost 850,000 homes have provided their details to Irish Water out of the estimated 1.5 million customers who will receive their first water bills in April.

There is no penalty for not registering by this time, but the default rate of €260 will apply to households with no confirmed details.

A spokeswoman for Irish Water told The Irish Times the utility would continue to accept confirmation from people or changes in their details after the deadline.

“People can confirm or change their details with us anytime. We’ll continue to do that beyond February 2nd. The earlier you give it to us the better so you get the correct bill. If you get a bill that has any aspect of it not right, get onto to us.”

About 35,000 households returned their registration packages with no details, according to the water company. This figure includes 20,000 unopened packs.

An estimated 400,000 households will not be required to pay bills because they have private wells and septic tanks.

All households, including those who are not Irish Water customers, are eligible to apply for the water conservation grant of €100, but they need to register with the utility in order to qualify.

The Department of Social Protection has set aside a budget of €130 million to pay for the €100 water conservation grant – equivalent to paying the fee to 1.3 million households.

The Department of Environment has confirmed to The Irish Times that there is no deadline for households to apply for this grant, which will be paid from September.

A statement from Irish Water said 1.065 million households had registered their details with the utility, which includes about 200,000 responses from homes who are not Irish Water customers.

All households, including those who are not Irish Water customers, are eligible to apply for the water conservation grant of €100 but need to register with Irish Water before they can apply for the grant.

“Approximately 79 per cent of those are on the public water main and therefore customers of Irish Water. This represents over 56 per cent of the total customer base,” the statement said.

Sinn Féin deputy leader Mary Lou McDonald said her party will not stand over a situation where people are charged for their domestic water supply.

“One of the really frustrating things in all of this debate is the government has set out their stall... and the shambles that is Irish Water,” she told RTÉ radio.

“We in opposition have spent all our time trying to row them back from that very flawed approach. They haven’t listened to us and have carried on regardless. And we’ve wasted a whole pile of parliamentary time and the time of public servants who have all of the facts and figures and all the data at their disposal arguing a flawed proposal rather than putting our heads together as parliamentarians and coming up with a proposal that’s fair. And that works,” she said.

Pressed on where the party would find the money to finance Irish Water, Ms McDonald said half would come from exchequer funding, some from commercial rates and the party would be open to “looking at all forms of formula”

“You would tailor the level of investment and works you could carry out on the basis of that formula,” she said.