After considering the growth of the area, the council entered into negotiations to modify the scope of the project.
The scheme currently services 2200 properties, with each paying about $1200 annually.
Chairman of commissioners John Robertson said the scheme was always meant to expand and the more people that were connected the better, as capital cost could be spread across the district.
Asked whether homeowners who were already connected to the scheme would be required to pay more, he said any extension would have little impact on them, although it was premature to say to what extent.
Mr Robertson expects the consultation process to be finished and options drawn up for the council to consider by the end of May or June.
But association chair Bruce Rogan described the expansion plan as a "complete farce".
"Modern standalone schemes can be extended but here they [KDC] have to spend $30 million again in order to cater for additional extension, and we'll have to pay a colossal amount again."
Mr Rogan said the council was arguing it needed to find some money before more residents could be connected to the system.
"This matter could also end up in court."