Just over 30% of the 1.6m eligible households have so far paid the €100 household charge, the agency responsible for its collection said today.
The Local Government Management Agency (LGMA) said that by 11.00am this morning some 493,899 households had registered to pay the charge.
However the LGMA also estimates that a further 56,000 registrations or payments are lying in postal bags that have yet to be processed.
The deadline for payment of the controversial tax is tomorrow, March 31.
LGMA Chief Executive Paul McSweeny said the agency is experiencing a surge in registrations today.
"The increase is mostly online," he said.
"85% are coming through online, 15% by post.
"There are still one million forms out there in circulation," he added.
"We expect that next week we will see quite a lot of those coming back."
However Rita Harold from the campaign against the tax said the overall low take-up rate shows people are making a point.
"Really it's irrelevant whether another 100,000 people, or whatever, register in the next day and a half," she said.
"I think that's totally irrelevant to the fact that people are furious about this tax.
"They are using it to fight back against the austerity agenda of the Government," she added.
"And the reality is that we are still going to have a majority of people refusing to pay, refusing to register, not giving over their personal details and standing up in opposition to this tax."
Speaking at a protest outside the LGMA offices in Dublin today, the Campaign Against Household Water Taxes (CAHWT) saluted what it called the "magnificent boycott" of the charge.
"This is the first mass movement in decades in Ireland to speak so loudly against an unjust measure," said John Lyons of the CAHWT.
"Ordinary people the length and breadth of this country have spoken," he added.
"The Government should now listen and abolish this tax,."
Mr Lyons added that in addition to those not registering, many who have done so state they are doing so under duress, fearful of the threats by Government.
"This is no way for a government to treat its people," he said.
The CAHWT has urged opponents to the charge to join a protest being held in Dublin tomorrow.
Protesters will gather at Parnell Square at 1pm before marching to the Fine Gael Ard Fheis.