The Prince William Board of Supervisors, acting on a recommendation by the county's sewer authority, has approved standardizing water and sewer rates throughout the county. The board's action will lower some residential bills and keep others unchanged.

The standardized rates, which became effective Monday, are the result of bringing the county's five sanitary districts under the umbrella of a Prince William Service Authority two years ago. At the time of consolidation, each district's rates remained unchanged.

Based on a study done by the Vienna engineering firm of BCM Potomac, service authority director Ray Spittle asked the supervisors to base all fees on the rates being charged in the old Occoquan-Woodbridge-Dumfries-Triangle Sanitary District, which takes in most of eastern Prince William except Dale City. Dale City sewer and water systems are operated by the privately owned Dale Service Corp., which is not subject to county rate standards.

Since 1978, residents in the Occoquan District have paid a monthly service charge of $2.25 for water, with $1.37 per 1,000 gallons used and a $2.50 monthly service charge for sewers plus $2.70 for each 1,000 gallons of water to pass through the sewer system.

In the Greater Manassas Sanitary District, customers who have been paying their bills quarterly at $18.15 for each 15,000 gallons of water used and $74.94 for each 15,000 gallons to go through county sewers will save about $9 a month at the new rate. Customers in the Yorkshire Sanitary District, who have been paying $18.75 for water and $67.25 for sewers, will save almost $12 a month.

Oak Ridge Sanitary District residents, who have paid $43.50 each for water and sewer use, will save almost $8 on their monthly bills. Because there are only wells in the Nokesville Sanitary District, there will continue to be no water charge but Nokesville residents hooked up to county sewer lines will pay a $2.50 service charge plus a flat sewer rate of $18.90 a month. They could realize a savings of almost $35.

In addition, customers in all but the Occoquan District have been paying a $10 penalty if their payments arrive later than 15 days past the due date. Under the new system, no late fee will be charged to delinquent customers. But service will be cut off after two warning notices, said service authority controller John Woodcock.

"We collected about $15,000 a year in late fees," Woodcock said. "But the cash flow wasn't very good under the quarterly billing system. Under the monthly system and with the warning letters in the Occoquan District, we found we had to cut off only about 30 customers a month out of 15,000. The improved cash flow will more than make up for the lost revenue," he said.

In another change, summer rates will differ from winter rates because water for swimming pools, car washing and lawn sprinkling does not flow through county sewer lines. The service authority will average a customer's bills for the months of January, February and March and will base the bills for June, July and August either on that average or on the actual sewer use, whichever is lower, Woodcock said. Customers with pools using 8,000 gallons or more will be asked to inform the authority of this, and they will receive a 20,000-gallon "credit" on their sewer bill.

"We'll lose about $500,000 a year with this method," Woodcock said, "but with a $28 million operating budget, that's a drop in the bucket. We don't have to make a profit and we don't need the money."

In other actions, the board reduced sewer and water hookup fees to home builders, also effective Monday. The new $2,500 tap fee represents a reduction of from $50 to more than $1,000, and it is lower than any in Northern Virginia, including Fairfax County, which charges more than $3,000 for the service. Tony Ahuja, president of the Northern Virginia Builders Association, has been lobbying for an even lower connection fee to keep construction costs down.