Wellington City Council says it's acceptable for councils to contract sewage to private companies for up to 35 years, but not drinking or storm water services.
Since 2002, such contracts have been limited to 15 years, but longer contracts would be allowed under the Local Government Amendment Bill.
Strategy and policy committee chairman Andy Foster says there are few savings to be made from allowing longer private contracts for drinking water.
But he says wastewater should be treated differently, because new sewage treatment plants are expensive and complicated to build.
Cr Foster also says fears that longer contracts will lead to privatisation are groundless.