The price of building a new house could rise by $2,240 if Napa Sanitation District approves a proposed hike in the connection fee paid by developers of new homes.

A consultant is recommending that the connection fee be increased 39.6 percent, from $5,660 to $7,900 per dwelling unit.

The intent is to have residential and commercial growth pay the cost of adding sewage treatment capacity, rather than sticking existing customers with the tab, Michael Abramson, the district’s general manager, said Thursday.

The district hasn’t raised connection fees since 1995. Since then, the district has spent nearly $68 million to expand treatment capacity, consultant Bartle Wells Associates reported.

Recognizing how controversial a major fee increase could be, the district’s finance committee told Abramson Monday to present a more comprehensive report on the need and how the $7,900 recommendation was calculated.

Napa Mayor Jill Techel, chairwoman of the district board, said she and fellow director Charles Gravett want staff to confer with business and building industry groups.

“What would the effect be of raising the fee at this point when we’re trying to get the economy going?” Techel said Thursday.

“Yes, developers need to pay their share,” she said. But a substantial increase when the construction sector is depressed could have unwanted consequences, she said.

She and Gravett asked for a comparison of how the new hook-up fees would compare with those charged in other towns.

Abramson said in an interview said the district in 2006 tackled sewer rates paid by current customers. The board of directors approved three years of 15 percent rate increases, following by annual increases matching changes in the cost-of-living index.

Now the district needs to bring hook-up fees in line with the cost of expanding system capacity in recent years, Abramson said.

The proposed $7,900 fee would apply to single family homes, each duplex unit and condo. Apartments and mobile homes would pay $4,740 per unit.

Commercial customers would pay higher hookup fees, as well.

Techel predicted it would be many months before higher connection fees are before the full board for adoption.