The water in Ashburton that could be taken by a bottling company is just a drop of what is beneath the Canterbury Plains, Canterbury Regional Council says.
NZ Pure Blue is negotiating with the Ashburton District Council to buy a section that comes with the right to extract water from local aquifers.
The council is selling a lot in a business estate, which comes with a resource consent for 45 litres of water per second to be extracted from the town's underground aquifers.
A group protesting against the sale, Bung the Bore, say the New Zealand-owned company shouldn't use water from a drought-prone area.
But the council's water manager, Tim Davie, said studies showed there was plenty of water in the aquifer for the town's supply and commercial use.
He said the water was pure and well worth bottling, despite reports saying some of the water in the area was so poor health warnings were periodically issued against it.
Water 250 metres below the surface was "much more pure", he said.