PLAISTOW — Francine Hart has lived in town for 34 years and says she has never had good well water.

“I personally have a nuclear power plant downstairs in my house because I have like 20 different tanks to refine it and clean it. It’s horrible, and we don’t even drink it,” said Hart, chairman of the board of selectmen.

The town has been plagued by poor water quality for years, but the board on Monday took the first step toward establishing a municipal water system with water from Manchester Water Works being delivered through a series of pipes stretching for 25 miles.

After extensive discussion among dozens of state and local officials and countless legal reviews, selectmen voted to sign an agreement establishing the Southern New Hampshire Regional Water Interconnection.

Town Manager Mark Pearson, who has worked closely on the $26.9 million project, called it a “historic agreement.”

The water sale agreement will run until 2058, said Phil Croasdale, director of Manchester Water Works. He said the Board of Water Commissioners approved the deal on March 28.

For the first 10 years, Plaistow and other area towns will purchase the water at the retail rate that Manchester charges its customers within city limits, currently $1.546 for 100 cubic feet of water, Croasdale said.

By the 15th year, the rate will ratchet up to the out-of-city rate, which is a 15 percent premium.

Croasdale said the water sales, which could eventually reach 3.13 million gallons a day, could end up covering the local costs of a water treatment plant that Water Works is preparing to build on the west shore of the Merrimack River.

“It puts us in a very good position for having a source of water for a couple of generations,” Croasdale said.

Other parties involved in the project are the towns of Derry, Salem and Windham, Pennichuck East Utility, and Hampstead Area Water Company.

Plaistow officials must still work out a plan for connecting users to the system, metering, policies and procedures, and hiring a water operator to oversee the municipal water system. Pearson said he expects those discussions will be held this fall.

“Truthfully, I never thought I’d see the day,” Selectman John Blinn Sr. said of the project that’s now coming to fruition.

Robert Scott, commissioner of the state Department of Environmental Services, said the regional water agreement was an “important milestone” and “unprecedented” in New Hampshire.

“All municipalities are making a commitment to funding and building infrastructure that’s going to benefit them, but also to maintain and operate it. Those are important components and that’s how we make sure this is something that will survive for the future generations,” he said.

The system will initially be able to serve 400 Plaistow homes and businesses now on private wells, including 56 properties with groundwater contaminated by the chemical MtBE.

The project will address MtBE contamination in Salem and Windham as well.

Salem town officials voted to sign on Monday, and Derry was scheduled to vote on Tuesday night, according to Clark Freise, deputy commissioner of environmental protection. Derry is the last party to consider the agreement, Freise said.

Construction is expected to begin next year, with the system online in 2021 or 2022.

Of the $26.9 million cost, $7 million will be related to Plaistow’s work and will be covered through federal and state funds, Hart said.

Croasdale said Manchester will continue to fluoridate its water, and the signatories recognize the fluoridation and won’t compel Water Works to stop it.

“Salem’s going to get water with fluoride in it,” he said, adding that no local officials expressed concern about fluoridation. According to the U.S. Centers for Disease Control, Salem does not currently fluoridate its public drinking water supply.

The agreement also says that if the water supply is threatened, for example by drought, Manchester and existing franchisees get priority, Croasdale said.

Plaistow will own and operate a pump station at the Atkinson/Plaistow town line.

The project will include 25 miles of piping from the Londonderry-Derry town line running to Plaistow — 70 percent of which already exists; up to six metering stations; four new or improved pumping stations; and two new water storage tanks.

Any piping that already exists in Plaistow is only used for fire suppression, but that would change once the system is online.

The series of pipes will eventually connect to Plaistow’s current infrastructure on Route 125 and will include a new section of pipe along Sweet Hill Road, where it will hook up to a new water tank. Piping will also be added to sections of Westville Road and Wentworth Avenue.

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Union Leader reporter Mark Hayward contributed to this article.