Forget the bathroom en suite, or the redoing the kitchen.

Suffolk County Executive Steve Bellone wants to spend $85,000 to determine whether high-tech septic systems will boost residential real estate values.

Sarah Lansdale, county planning director, said officials want to hire CoreLogic, a California-based company, to determine if the new septic systems could add to a home’s sales potential.

“Right now there is no value assigned to sewer connections in appraising the value of a house, let alone more recently installed . . .,” high-tech septic systems, said Lansdale, who called the study the first of its kind nationally. “The key will be presenting the value proposition to the homeowner.”

The county is hoping the study can be used to convince the 360,000 homeowners in unsewered areas to install new septic systems, which can remove up to 70 percent of the nitrogen from waste water.

The systems cost $14,500 to $17,500, compared with $3,000 for conventional systems that do little to curb nitrogen pollution that damages lakes, streams and bays.

Builders also say such systems can require $5,000 in design and permitting fees. Bellone has proposed a program to provide grants and loans of up to $21,000, but an initial $2 million is enough for only 400 homes.

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Because there are so few of the new systems in Suffolk, the county is looking to compare sales in areas of Maryland and Rhode Island that “have developed robust septic upgrade programs,” Lansdale said.

She said real estate officials in other areas say residents advertise such systems or connections to sewers, particularly in low lying areas. Officials also say such systems can be designed to water lawns with waste water.

“Right now we have anecdotal evidence there’s a benefit; we’d like to have empirical evidence,” Lansdale said.

Mitch Pally, executive director of the Long Island Builders Institute, said determining the added value of high-tech septic systems may be difficult in a county where the prime factor for home prices is the quality of local school districts.

“How do you determine this on top of that?” he asked.

Lansdale said funding for the study will come from a state department of Environmental Conservation grant.

Paul Sabatino, an attorney who is suing Suffolk County on behalf of Southwest Sewer District residents who claim sewer taxes have been misspent, questioned whether the county can legally subsidize individual home septic systems or do studies to show economic benefit.

“It doesn’t sound [like] legitimate government expenditure because the county is not in the business of marketing private properties to enhance their values,” Sabatino said. “And it’s totally unfair to people in sewer districts who are overtaxed, and those outside district who paid for their own septic systems at their own expense.”