The Fairfax County Board of Supervisors appropriated $2.45 million yesterday as a refund to developers on sewer hookup fees they had paid since January 1978.

The refund is part of an out-of-court settlement of a suit brought by Northern Virginia developers who had charged that the $1,500 hookup fee imposed in 1978 was excessive. The county agreed to roll back the fee to $1,350. Before the 1978 increase, the fee -- which is used to help cover the cost of new sewer facilities -- was $1,000.

According to Cecil M. Buyer Jr., new president of the Northern Virginia Builders Association, little, if any, of the money will have to be refunded to homeowners because most of the $1,500 tap fees were paid for projects not yet started. Any refunds to homeowners, he said, would have to reflect legal and professional fees -- estimated at $250,000 -- incurred by the developers in their suit.

Buyer said experts hired by the builders had estimated that the tap fee should not be higher than $500. He said the builders agreed to accept a $1,350 "so as not to bankrupt the county."

In addition, he said, builders won agreement from the county that a specified methdology would be used to set future tap fees, "rather than let them be set in the political arena."

The question of how much the county charges for sewer hookups became a politically charged issue in 1978 when Fairfax Supervisor Audrey Moore (D-Annandale), a long-time advocate of more controls on growth charged that county officials, in deciding to keep the tap fee at $1,000 and raising the service rate instead, were giving developers a break.

Angered by her stand, the rest of the board abstained, letting her single-handedly enact a $2,250 tap fee. Later they repealed that rate, and set the fee at $1,500.