Under the current bill, South Taranaki would become a part of the Central-Western entity, made up of 22 councils from the Waikato, Bay of Plenty and Taranaki regions and the Ruapehu, Rangitīkei and Whanganui Districts.
Nixon said his council had a good track record of building, maintaining and operating three waters assets.
"We certainly have the financial capacity to continue to do this and under our own long-term plan we would have achieved the outcomes Government is seeking well before 2050," he said.
As well as this, Nixon said the degree of funding claimed to be needed had been considerably overstated, and the savings under the proposal were highly implausible.
He was also disappointed with the government's handling of the proposed reform and said there had been no meaningful consultation with iwi, council, or South Taranaki from the government.
"The promise of opting out was taken away from us, and it's been councils that have had to continue to engage in good faith and not the other way around."
He hoped the Government took the considerations of the council seriously.