The Central Hawke's Bay District Council faces a mighty repair bill to fix its new wastewater treatment plants.

The faulty plants in Waipukurau and Waipawa are dumping treated sewage into the Tukituki River.

They've already cost the council more than $8 million to build and repair, and resulted in breaches of resource consent conditions.

A new report now shows fixing them will cost ratepayers between $11 million and $20 million.

Mayor Alex Walker said they simply can't afford that.

"We have side wastewater treatment plants, we have seven water treatment plants across a very small population and so affordability of this major infrastructure is a real issue for us."

Walker said they will have to talk to the government about financial solutions.

"Our regional partners, our regional council partners and potentially central government, we may need to have some serious conversations about how do we deal with this".