A new community group plans to lobby Tamworth Regional Council to abandon plans for Dungowan Dam and spend the money on cheaper water improvements.
Lyn Allen, Robyn Bird and Bev Smiles said recycled water was one available answer to the city's woes.
By contrast the Dungowan project could prove to be a $484 million white elephant, they claim.
The business case for the project, which is due to be released in June 2021, might even demonstrate the project is unviable.
"The investment in a 22-gigalitre puddle is not going to solve the problem when the investment in additional 38 gigalitres with raising Chaffey Dam, which was then supposed to secure Tamworth's water supply, didn't," Bev Smiles said.
"The key problem is the way water's managed, not the volumes in storage happily evaporating."
The Tamworth Water Security Alliance called on Tamworth council to investigate water security options that are "cheaper, more sustainable and offer better water security than the very expensive Dungowan Dam," in the words of Lyn Allen.
Residents of the City of Perth drink recycled water, with Lismore council considering becoming the first in NSW to introduce it to the water supply.
There is also increasing appetite in NSW Parliament for the idea of using recycled water in parched communities.
Northern Tablelands MP Adam Marshall last year said treating wastewater was a "brilliant water security measure" worth investigation, which he would back politically and financially.
A report to Tamworth council last year said the idea would be too costly, adding as much as 50 per cent to the price of water.
But the group said the report should be made public.
And, they rejected a perception the community wouldn't like the idea.
"What we're saying is that Tamworth council has not asked the community 'do you support recycling water for potable use or for any other use?'" Mrs Smiles said.
"We're saying they really need to look at the full options.
"If the choice is no water or Level 5 restrictions forever, or having the option of potable, reclaimed or renewed water, then the community hasn't been asked that question."
The group lobbied councillors before Tuesday's regular meeting, presenting eight alternatives to the Dungowan upgrade.
They have also engaged with Water NSW webinars and have written a submission to a parliamentary inquiry into dams.
The new dam would also impose substation environmental costs on a river which feeds the Murray-Darling basin system, they said.