The proposed increases would come on top of substantial increases imposed by the commissioners on most customers last year.
In some areas, sewer rates jumped by as much as 93 percent and water rates by as much as 226 percent.
The county has about 8,600 water and sewer accounts.
Public Works Director Gary Rohrer said the increases proposed for July 1 were lower than expected for a couple of reasons.
The county shifted $300,000 into the sewer budget from funds intended for the water budget and the county's industrial pretreatment plant.
That helped keep sewer increases below the expected 16 to 17 percent hike, he said.
Another major reason for the smaller than expected increases is that a consultant who drew up a study last year overestimated the cost of refinancing the department's debt, county officials said.
That meant the county didn't need as much revenue as projected, Rohrer said.
"This is a giant step forward compared to where we were last year," said County Administrator Rodney Shoop.
"This department was on its knees," Rohrer said. "Now it's on it's feet."
Rohrer said the department had higher morale, and was focusing on preventive maintenance and customer service.
Commissioner John S. Shank said he could live with the water rate increases but said he'd like to pare the sewer increases to a couple of percent, possibly by increasing commercial rates.
Commissioner James R. Wade asked the staff to find out how much residential rates could be offset by increasing commercial rates.
They are to discuss the increases again next Tuesday.
Despite the increases, the proposed Water and Sewer Department still has a projected $888,000 deficit for the county's industrial pretreatment plant.
Expenses and debt payments projected for next year on the plant are more than triple the projected $372,000 in revenue.
The plant is operating under capacity and could require $2 million in work in 1999, according to county officials.