The Bill, which asks for ownership of the Otama rural water supply scheme, near Gore, to be transferred to resident users, passed its first reading earlier this month.
New Zealand First list MP Mark Patterson is sponsoring the Bill.
Mr Patterson said the scheme had been run by a committee of users with representation from the Gore District Council, but there was ambiguity over its ownership.
In a referendum last year, Otama water scheme users voted to take ownership of the scheme.
The committee plans to set up an ownership company and hire a private contractor to operate it.
This change requires an Act of Parliament.
Voters in the referendum turned down the option of having the Gore District Council continue to govern, manage and operate the scheme via a council subcommittee.
Mr and Mrs Miller are longtime Otama residents and have been involved in the scheme since its inception.
''The actual tanks and everything is on part of our farm,'' Mrs Miller said.
Like many other farmers in the area, Mr Miller had taken a turn on the scheme's governing committee.
The scheme serviced not only the stock in the area but also households and it was built using the area's labour force, Mrs Miller said.
The decision to use the aquifer was made because of the purity of the water source, she said.
''There was the odd occasion when we got E. coli in it.''
Contaminated run-off making its way into the bore had been the source of the E. coli, but that had been mitigated by carrying out remedial ground work around the site and fencing it off, she said.
Mr Miller said the help of residents to install the system had been invaluable.
''That got things going.''
The aquifer feeding the scheme was not connected to the Mataura River, he said.
''It's really good water - it would have to be one of the best schemes out there.''
The book The Knapdale Run, edited by Elizabeth Kerse, says the introduction of more scientific farming methods and higher stock-carrying capacity led to the need for a constant water supply in the area.
''By the '60s rural water schemes had been introduced in North Otago, but the Otama scheme was the first to be mooted in Southland,'' the book says.
Initially, the supply was limited to an area of 15,000 acres [6070ha] but grew to encompass more than 73,000 acres.
Funding for the scheme came from a Ministry of Works subsidy. The remainder of the finance came from a loan raised by the Southland County Council and from contributions paid by consumers.
''The actual work of laying pipes was begun in November 1972 with some 33km of asbestos pipe being laid in trenches dug with the county grader,'' the book stated.
Southern Rural Life