MANSFIELD - The average Mansfield family of four will see its sewer bill increase by $80 this summer and its water bill rise by $18 under new rates approved by selectmen.

The $80 and $18 estimates are for a family that uses 11,000 cubic feet of waste and water per year. Under 2008 rates, that family would pay $371 annually for water and $397 per year for sewer.

With the new rates approved last week, that same family will pay $390 for water each year and $476 for sewer.

The 20 percent hike in sewer rates is the last of three years' worth of increases that will fund improvements to the wastewater treatment plant, Public Works Director Lee Azinheira said. Sewer rates are projected to increase 12 percent next summer, and 6 percent in each of the five years after that.

Water rates will rise by 5 percent next summer, slightly more than the 4 percent increases over the past few years, because of reduced revenue projections for new water hookups, Azinheira said. "Also, for next year we will have to revisit this and may need to increase the (water) rates further and/or scale back the planned capital improvements," he added in a memo to selectmen.

Although the board approved the new rates, selectmen expressed concern about the impact of the price increases.

"Between the sewer rates and the water rates, and we're talking about a debt exclusion, it's a lot of money for the taxpayer or the ratepayer," said newly elected Selectman Jess Aptowitz.

Azinheira said he is working to keep rates down. "I tell you, I'm holding off as much as I can," he said.

Selectman George Dentino also expressed concern about whether the proposed water department budget will provide enough revenue for its operations. "This is the first budget I ever thought was too tight," he said.

If the water department needs more money, it will take it out of its reserves, Azinheira said.

TED NESI covers Mansfield for The Sun Chronicle. He can be reached at tnesi@thesunchronicle.com or 508-236-0333.