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The Dunedin City Council plans to spend millions fixing private stormwater infrastructure being overwhelmed by flooding across the city.

It has also unveiled a major review of who is responsible for privately owned stormwater, wastewater and drinking water pipes - known as ''laterals'' - connecting to council water infrastructure.

• Constant floods ruin quality of life 

The shake-up comes amid concerns about ageing water infrastructure, the pressure placed on existing private watercourses by new developments, and climate change forecasts of more frequent extreme weather.

A staff report presented to this week's council infrastructure services and networks committee meeting outlined the need for both steps.

The council had received 250 complaints from private landowners since the 2017 floods, many of which related to private watercourses - including pipes - being overwhelmed by increasing stormwater flows.

The resulting floods posed a risk to property, people, or both, the report said.

As a result, the council wanted to bring forward $3.5 million in funding to its 2019-20 budget, to pay for stormwater improvements across the city.

It has already identified 19 ''significant projects'', all relating to private watercourses, needing to be addressed over the next two or three years.

The extent of the problems were highlighted at Monday's committee meeting by Otago Peninsula property owners Cathy and Alex Shemansky and Waikouaiti resident Elaine Sternburg, who gave presentations on their flooding problems.

Mrs Sternburg was close to tears as she explained the toll wrought by the repeated and ''horrendous'' flooding of her Waikouaiti home.

''It's extremely stressful, I assure you,'' she told councillors.

''I need this issue to be resolved. It's been put in the too-hard basket for too long.''

Council 3 Waters group manager Tom Dyer told the meeting the extra funding - subject to annual plan consultation - would not cover the full cost of work needed.

He could not predict the size of the total bill, but significant storms in recent years had ``certainly brought the issue to a head''.

While the stormwater improvements progressed, the council would also review its existing policy on who was responsible for connections between council-owned and private pipes.

The issue, raised repeatedly in the past, emerged again late last year when Northeast Valley resident Sam Sharpe refused to pay for repairs to a leaking water toby.

The toby was on a private pipe connecting his and neighbouring houses to the council water main, but under a private right-of-way not owned by Mr Sharpe, and both sides had refused to pay.

The council staff report said such issues had ``long been a matter of contention'', but community expectations were shifting.

Property owners also often had no incentive, or ability, to co-ordinate and pay for what could be expensive repairs to pipes under council roads.

The council, if it assumed responsibility for such work, could achieve savings of up to 50% by doing the work in bulk when upgrading other infrastructure, Mr Dyer said.

Without action, the failure of private pipes could trigger wider problems, such as allowing groundwater into the wastewater network and overwhelming the system's capacity, he said.

The frequency of private infrastructure failures was also increasing, meaning the existing policy might not be delivering "the best overall outcomes for the city''.

Councillors voted to note the review, which was expected to take two years to complete, and the new approach to stormwater work in the meantime.

chris.morris@odt.co.nz