That's according to Minister for Water Melinda Pavey, who made the commitment in an Estimates hearing on Monday.

"The cost burden will not be put on the town or farmers," she said.

"There will be benefits that will come to farmers and they will be part of that process. But until we have the final business case, I don't expect the water bills for the community of Tamworth to change."

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Farmers and residents - and the Tamworth Regional Council - have long been concerned the enormously expensive new water infrastructure could only be depreciated by increasing water rates.

The opposition last year warned locals water bills could increase by "$2000 to $3000 a year".

Peel Valley water users already pay among the state's steepest water bills.

Under questioning by Shooters, Fishers and Farmers MLC Mark Banasiak the minister promised not to recover the cost of depreciation by raising water rates further.

Minister Pavey also told the committee she rejected concerns that the project could be canned by a future Labor government if work isn't underway quickly.

"I think the information will stack up for itself. It really will," she said.

A future government would need to spend hundreds of millions repairing the existing Dungowan Dam anyway, she said.

Member for New England Barnaby Joyce told the Leader last month he was concerned a federal election could return a Labor government, which could pull the plug on the project.

A Productivity Commission inquiry into the project found the government could buy an equivalent amount of water as the dam would save for less than $10 million. Even a modest cost blowout would render the project unviable, it said.

Mrs Pavey told Monday's hearing she was "offended" by the report.

The project does not yet have a business case and is not expected to get one until the end of the year. It will be two years since a joint commitment of Federal and state funding in October.

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