If introduced, Labour's policy could cause some products to rise in price. But the poll showed that a strong majority were in favour of the idea even if they were hit in the pocket when buying groceries.
Support for a water royalty is highest in Auckland, where 73 per cent of people back the move.
It is lowest in Canterbury, which would bear the brunt of any price on freshwater because the farming industry is heavily dependent on irrigation.
But Cantabrians are still strongly in favour of the initiative, with 68 per cent saying they would back it.
A charge on freshwater is most popular among older voters, with nearly three in four people over 60 saying they supported it.
Labour expects to raise $100 million a year through the policy, which would be spent in the area the revenue was generated to improve water quality in rivers, lakes and streams.
The National Party opposes a price on freshwater, saying it would hurt key industries and would be difficult to implement. The National-led Government has asked officials to explore the options for applying a charge to water which is bottled for export, but has all but ruled out applying any charge more broadly.
Prime Minister Bill English also says Labour has "blundered" into the debate about charging for water without considering its impact on Maori rights and interests in water.
If in Government, Labour says it would hold talks within 100 days to determine how much industries would pay and how the iwi issues could be resolved.
Herald analysis found a charge of 2c per cubic metre would mean a 100ha farm would pay around $8000 a year more in tax.
