A proposal to charge Far North ratepayers a single district-wide rate for sewage would save households in some towns thousands of dollars while others would see their rates jump by hundreds of dollars a year.

In the current system, the amount households pay for sewage is different in every town, depending on the cost of building the treatment plant, whether it’s still being paid off, and the number of homes hooked up to it.

In general small towns are hit the hardest by sewage and water rates because they have fewer ratepayers to share the cost.

Big towns, on the other hand, can split the costs — which can total many millions of dollars even for a modest treatment plant — between a larger number of ratepayers.

A similar situation applies to the cost of connecting to town water supplies.

Currently, wastewater rates in the Far North range from a low of $872 per household per year (Kaitāia/Awanui) to a maximum of $1276 (Kerikeri). The high rate in Kerikeri reflects the fact a new plant has just been built, at a cost of $27 million, and is still being paid off.

If the current rating system continues, by 2025/26 the lowest rate, $1015, will be paid by Rangiputa residents while Hihi households will be hit with an eye-watering $4270.

However, if the change goes ahead, all Far North households that can connect to a wastewater system will pay a flat rate of $997 in 2022/23. The rate for water will be $291.

By 2025/26 the district-wide rate for wastewater would be $1307 while a water connection would cost $508.

The big winner under the proposed change would be Hihi, where rates would be $2963 lower in 2025/26 than under the current scheme-by-scheme rating system. Ōpononi/Ōmāpere and Kohukohu would also be significantly better off, by $562 and $324, respectively.

The losers would be Rangiputa, where rates would be $292 higher by 2025/26, and Awanui and Whatuwhiwhi, with increases of about $250. Households not connected to sewage or town water schemes would not be affected.

A big question mark, however, hangs over the impact on Kawakawa and Kaikohe.

Although both are low-income towns they could be hit with significant cost increases due to upgrades to their wastewater plants and town water supplies, which are required before planned affordable housing projects can go ahead.

A rough estimate by the Far North District Council suggests rates will go up by $578 in Kaikohe and a whopping $1078 in Kawakawa if the current rating system is maintained.

If, however, the council switches to a district-wide rating system the increase would be a more modest $200 in each town.

It was not clear when those increases would take effect.

Councillor Felicity Foy, who chaired the infrastructure committee in the council’s previous term, said a district-wide rating system would allow the council to plan better for replacing its ageing treatment plants — regardless of whether or not the government’s Three Waters reforms went ahead — while also spreading the cost around the district.

The Far North was unusual in that it had a large number of small wastewater and water treatment plants.

Whangārei, on the other hand, had a large sewage plant that served much of the district’s population, which meant the cost could be more easily spread.

Households that weren’t connected to council sewage or water schemes wouldn’t be affected by the proposal, Foy said.

The Hihi Residents and Ratepayers Association, where wastewater rates have been a bone of contention since at least the 1980s, has welcomed the proposal.

Chairman Roger Marsh said the council’s chief executive had recently briefed locals on the proposal.

“The way he presented it, most of the effluent from various schemes ends up eventually in the sea, and we have a joint interest in keeping the sea in good condition,” he said.

“Region-wide rating would be fairer for everyone. It certainly makes a difference for us, though we’re just the first cab off the rank in terms of our wastewater scheme needing to be upgraded.”

The association was still negotiating with the council about an affordable upgrade and was receiving expert technical advice as well as support from local iwi.

The council’s original proposal would have cost about $6m despite Hihi having just 192 toilet pans, Marsh said.

Kaikohe’s treatment plant was also in need of a significant upgrade but the cost, even with Government assistance, would be “out of their league” if residents couldn’t share the cost across the district, he said.