Two thirds of homeowners do not believe the proposed 'free allowance' of water will cover their daily needs when charges are introduced next week, according to a Sunday Independent/Millward Brown survey.
Households will be given 30,000 litres of free water per year when Irish Water begin billing people from the start of October.
An additional allowance will be given to families with children under 18-years-old.
It was initially suggested the free children's allowance would be 38,000 litres per child per year, but this was cut to 21,000 litres.
The Government has proposed an average water charge of €240 per year after households use their free allowance .
However, the majority of people surveyed in our poll last week do not believe their daily water needs will be covered by the free allowance proposed by the new State utility company.
Just one in seven people believe the free allowance would cover their water usage.
People older than 55 were more likely to believe the allowance would be sufficient, according the poll. Sinn Fein and Independent voters were less likely to believe the free allowance was enough.
Fianna Fail finance spokesman Michael McGrath said the Government's claim the average bill would be €240 was "absolutely bogus".
Mr McGrath insisted families with two children will receive bills exceeding €600 a year when the charges are introduced next month.
Final water charge prices have yet to decided but it is hoped they will be agreed next week.
In January, every household in the country will receive an assessed water charge for the first three months of the scheme. A single person living on their own will be charged €48 and two adults will be charged €70.
Bills will be broken down between drinking water and waste water usage.
People with medical conditions requiring large amounts of water consumption will be entitled to a capped charge.
A family of two adults will pay a capped charge of €278 a year for drinking water and wastewater, while a house with four adults will pay €482.
Last week it emerged people applying for the capped charge would only have to tick a box on an application form to receive the discounted water rates.
It has yet to be decided what medical conditions will be included and it is not expected to be clarified until 2016. The discount will be operated on an 'honesty system' but critics say the scheme is open to abuse.
Discounts will also be applied for people living in areas where water is not safe for consumption.
Plans are being drawn up to increase discounts for people on 'boil water notices'.
Under the current scheme, people who cannot drink water provided by the State will receive a 25pc discount.
If water continues to be unsafe for more than three months the discount will increase to 50pc.
Households, where drinking water is unsafe, still pay full price for waste water supply.
In cases where households can provide their own waste water services, an initial 50pc discount is applied when water is unsafe to drink and then a 100pc discount after three months.
Environment Minister Alan Kelly said the regulator is currently considering the situation faced by households where water is not safe for consumption.
"I understand that, following the public consultation process, the regulator is now further considering the approach to compensating households, where the water supply is not fit for human consumption," he said last week.
It is hoped people will not have to pay anything for unsafe water when new charges are agreed. The majority of those affected by 'boil water notices' are living in Roscommon.
The Government is facing a by-election in Roscommon South Leitrim next month and water conditions in the area will be a major concern to voters.
The poll findings come after an Irish Water contractor last week obtained a High Court injunction against protesters preventing the installation of water meters.
The order sought by GMC Sierra was taken against nine Dublin based demonstrators who the contractor claims "intimidated and assaulted" workers trying to install meters.
In High Court affidavits, the company claimed workers have been "threatened" and "head-butted". The court was shown video evidence which claimed to show protesters intimidating workers.