Fairfax City authorities said this week that they are ready to get out of the water business.

They have operated their own water utility for years, charging far higher rates than those charged to county residents. Now, Fairfax City has reached a tentative agreement with the Fairfax County Water Authority to join the county system. The agreement, the city says, will provide its residents with less-expensive, higher-quality water.

The pact also could end the third, and final, battle in a very messy fight between the county and the independent water utilities operated by the city of Falls Church, the town of Vienna and Fairfax City. At this time last year, all four parties were either issuing declarations or filing lawsuits over water. Now Falls Church, Vienna and Fairfax City have taken steps in recent months to dismantle their water utilities and join Fairfax Water in one large company that would serve everyone in the county.

Fairfax City will have to pay Fairfax Water $20 million to join its system, City Manager Robert Sisson said. But the city hopes to sell its reservoir and treatment plant in Loudoun County and recover most, if not all, of that cost. The city plans to have public hearings on March 21 and April 6, and the City Council will vote on the idea April 9.

A deal would end a water-rate disparity that has existed, and angered many, for years. In 2011, one study showed, the average quarterly bill for residential customers of Fairfax Water was $57.31. But for Falls Church customers, including 30,000 actually located in the county, it was $86.55. Vienna customers paid $100.16 per quarter (its county residents paid even more), and Fairfax City customers paid $103. Fairfax City has about 8,300 customers in the city and about 3,250 in the county.

Vienna was the first water company to make the change, announcing an agreement in September to begin taking water from Fairfax Water, and connect to Fairfax completely by 2015, at a cost of $15 million. In November, Falls Church, which had been battling the county in the courts for years, agreed to sell its utility to Fairfax for $40 million, subject to a referendum this November.

“Hopefully, in the end we’ll have peace on Earth with uniformly low rates and improved delivery of water to all of our residents within the footprint of Fairfax County,” said Board of Supervisors Chairman Sharon Bulova (D).

The peace was partly brokered by U.S. Magistrate Judge Theresa C. Buchanan, who was thrown into the middle of a complicated federal lawsuit. Tired of seeing county residents pay much more for water just because they were served by Falls Church, Vienna or Fairfax City, Bulova and the county issued a decree (or “ordinance”) that the county would set the water rates for all of its residents. Falls Church, Vienna and Fairfax City responded by suing the county.

The county and the municipalities went into mediation with Buchanan, after which Falls Church and Fairfax City credited her with helping them reach agreements with the county.

Fairfax City is charging its residential customers $4.61 per 1,000 gallons, compared with Fairfax Water’s rate of $2.51. At an estimated use of 100,000 gallons per year, that’s $461 for city residents and $251 for county residents.

“This is a good deal for anyone who gets water from us,” City Council member Dan Drummond said. He acknowledged that many city residents had a sense of civic pride about the city running its own water system. But he said that because there is an option to go cheaper and cleaner, the city is putting it out to the public. If approved, rate changes still might not be seen until 2015.