Lion Nathan corporate affairs director Liz Read said the company was asking for donations of 10c a litre of water to go towards the Speight's Brewery Environment Fund.
As brewing was "resource intensive" through water use and created waste through packaging, she believed it appropriate a charitable fund for the environment be set up.
Preference would be given to initiatives involving the preservation and protection of local water resources and environments.
With about 1 million litres of water being taken from the spring annually, the fund would receive $100,000 from the public.
Speight's would contribute an annual sum of $25,000 and proceeds from the sale of water bottles on site would boost the fund to $130,000.
"We thought that people would feel that 10c wasn't onerous and, given that the money would go direct to environmental projects in the Dunedin area, it would be difficult for anyone to object," Ms Read said.
Dunedin woman Grace Burt used the tap for health reasons and said it had been "brilliant" getting the water for free.
But if a donation was asked for, she would pay.
Carl Burgess, who had been using the tap for about 15 years, said asking for a donation was "fair enough" and he would also oblige.
The fund will be launched with a function tonight.
Applications for use of an initial $25,000, to be awarded in October, are now open.
Annual applications to the fund will open in March and amounts will be awarded every year on June 6, the date James Speight was granted a brewing licence for the Rattray St site.
