N.H. Rev. Stat. Ann. § 38:3-a

Any regional water district may initially establish such a plant after 2/3 of the members of the governing body of the district shall have voted affirmatively, and a majority of the constituent municipalities of the district by a majority vote of their legislative bodies have confirmed that vote. Such confirming vote shall create a rebuttable presumption that such action is in the public interest. If the vote is unfavorable, the question shall not be again submitted to the constituent municipalities within 2 years thereafter.