Homeowners illegally siphoning off a share of Dunedin's water supply without paying could be slapped with backdated bills.
The warning comes as council staff confirm they are investigating up to 170 "suspect" connections, involving properties with either illegal or informal connections to the council's reticulated network.
Council asset planning manager Laura McElhone said yesterday some of the connections dated back more than 30 years.
"We have identified 52 who have not been paying for water at all, and four who have only been paying a half water charge.
"The remainder have been paying, but the arrangement of their supply is such that it would not be allowed under current policies and design standards."
It was "virtually impossible" to calculate the exact amount of revenue the council had lost, but a rough estimate - based on all the properties paying the standard annual water charge of $383 - amounted to about $20,000 each year, she said.
Council staff were still investigating, but Dr McElhone said those found to have deliberately and illegally connected their homes to the council's mains could eventually receive a backdated bill.
Under the council's water supply bylaw 2008, staff could retrospectively adjust inaccurate billing in favour of the customer or the council, up to a maximum of 12 months, she said.
Other options available included forcibly removing properties from the council's supply.
"We have the power to disconnect. That's not to say we will apply that power," she said.
Any decision would be made by councillors - not council staff - and only after a report outlining the options was considered by the council's infrastructure services committee.
That was expected to happen when the committee met next on June 14, or at the subsequent meeting on July 19, she said.
News of the investigation emerged after Cr Dave Cull, at Monday's committee meeting, admitted he was one of those homeowners with an illegal connection to the city's supply.
He chose to out himself as councillors debated whether changes to the existing bylaw were needed to accommodate "exceptions".
The bylaw prevented property owners outside existing water supply zones from connecting to council water pipes to stop the spread of unwanted subdivisions along pipelines.
Dr McElhone said there was "no suggestion of any foul play" involving Cr Cull's connection, as it appeared his attempts to inform council staff had "for whatever reason" not reached the appropriate staff.
Many of the city's illegal and informal connections were the result of a variety of informal agreements with council staff, not properly recorded, and some deliberately illegal acts, she said.
