Potomac billionaire Mitchell Rales won a major victory Tuesday in his quest for a sewer connection for his Glenstone art gallery, a collection of abstract expressionists’ work widely viewed as one of the most significant in private hands.

In a nonbinding straw vote, the nine-member Montgomery County Council gave unanimous approval to Rales’s sewer request, which he has said would help him build an even bigger gallery on his 200-acre estate off Glen Road.

The council is expected to formally approve the request this month.

“We continue to be optimistic,” said Charles Maier, a spokesman for Rales. “We are not there yet, but we are pleased with what was said at the council.”

Glenstone is a little-known gallery that is open Thursdays and Fridays by appointment only. Rales, 55, who co-founded the highly successful Danaher, a manufacturing giant, has said he would eventually like to build another gallery that would rival the size and scope of the East Building of the National Gallery of Art.

Mitchell Rales stands third from left. (Margot I. Schulman/STRATHMORE)

The council also voiced no objections to a sewer request from Shri Mangal Mandir, a Hindu temple in Silver Spring. At the same time, the council turned down sewer requests from two homeowners who live near Glenstone.

All are in areas of the county where sewer has been banned by the county Planning Board and the County Council in favor of septic systems to restrict development. But under some circumstances, the council has approved sewer requests for private nonprofits such as religious institutions and schools.

Rales and his wife, Emily Wei Rales, Glenstone’s director, have said they prefer sewer because the life span of septic systems is typically 25 to 50 years. Under the terms approved Tuesday, the sewer connection would be for the art galleries and related structures only — not his house, which is also on the property.

The Glenstone sewer request renewed debate in Montgomery over efforts to limit development.

The Planning Board in May turned down all the sewer requests, noting that they violate local land-use policies.

“You don’t want to create the impression that all policies are valid only so long as an especially enticing proposal is not placed before you,” Royce Hanson, a former chairman of the county Planning Board and a nationally recognized land-use expert, said in an interview.

The administration of County Executive Isiah Leggett (D) supported the requests of Glenstone and of the Hindu temple. The Maryland environment department will review them next.

The request also has led to claims that Rales is getting special treatment because of his wealth and connections.

He has been a generous donor to local politicians, and his brother, Josh, a former candidate for U.S. Senate from Maryland, has helped him meet local decision makers.

“Heads have been turned. It is just too bad that it is politics in Montgomery as usual,” said Dolores Milmoe of the Audubon Naturalist Society. “Money paves the way for just about anything you want to do.”

Council President Roger Berliner (D-Potomac-Bethesda), who shepherded the sewer requests as chairman of the council’s environment committee, said during Tuesday’s debate that he is “offended by the suggestion that this council is kowtowing to the desire of a billionaire.

“What this council is doing is following its policy, looking at the pros and cons, the environmental benefits,” he said.

Opponents have said that Rales could construct his planned new 125,000-square-foot gallery and still have room for a six-acre septic field. They also noted that the proposed sewer line would cross an environmentally vulnerable stream that the county years ago had vowed to protect. Rales has said he would use highly sophisticated technology to protect the stream.