The Fairfax County Water Authority yesterday offered to buy the Falls Church Water System, a move that county officials said would save $45 a year for each of about 30,000 households in Falls Church and northeastern Fairfax County.

Residents in the McLean, Tysons Corner and Seven Corners areas of the county, who now receive water from the Falls Church system, would be the primary beneficiaries of the sale, if it is accepted by the city, the officials said.

The county authority offered to buy the Falls Church system for $5.7 million in cash, or $575,000 a year over 50 years -- whichever Falls Church chooses.

Falls Church officials said yesterday they have not been contacted by the Fairfax County Water Authority, and knew nothing of the proposed buy-out.

"If you put it in private sector terms," said Falls Church city manager Anthony H. Griffin, "I guess you could say it's an unfriendly takeover attempt."

Griffin said the Falls Church City Council would consider the offer once it is transmitted.

Fairfax County politicians long have complained that the City of Falls Church, which supplies water to 10,000 of its own residents as well as about 90,000 county residents, keeps its tax rate low with water revenue from county customers.

The water rate in Falls Church is about 55 percent higher than that charged by the Fairfax water authority.

Fred C. Morin, chairman of the Fairfax water authority, said the rate reduction would be possible if the buy-out goes through because "we're not in it to make a profit."

"We would give serious consideration to a proposal which matched the benefits we get from the system now," said Griffin. "But they have never come to us and said, 'What would it take for you to give up your water system?' "

Last December, when the county Board of Supervisors raised the possibility of a buy-out, Falls Church public utilities director Joseph Livinski said, "The city has no interest in such an arrangement." The county board endorsed the buy-out at a meeting yesterday.

Fairfax water authority officials said that if the acquisition goes through, they would be able to correct reported water-supply problems in McLean, where they said residents have complained of low water-pressure, as well as reported problems in service reliability in Tysons Corner and Pimmit Hills.

County residents served by the Falls Church system pay an average of $1.35 per thousand gallons of water, compared to the 86 cents per thousand gallons charged to county residents by the Fairfax County Water Authority.

"Our system's not perfect," said Griffin, "but we are not aware of very many customer complaints."

Griffin also pointed out that the Fairfax authority already supplies water to Alexandria and to Prince William County, adding: "I'm just wondering where the water authority's going to stop."

Morin hinted that the Fairfax authority may be open to compromise with Falls Church over the deal. "We're willing to talk to them about this offer," he said.

The proposal now goes to the Fairfax County Water Board, which is expected to approve it overwhelmingly at its meeting Thursday night. It will then be transmitted to Falls Church, officials said.