The Halifax Regional School Board is pulling the plug on the steam heating system at Citadel High School. It has issued a tender to convert to natural gas. (CBC)

The Halifax Regional School Board is walking away from a "green," but troubled steam heating system used in the $32 million Citadel High School.

The board issued a call for proposals Tuesday to convert the seven-year-old school to natural gas.

"We think it would provide us with a more reliable source of heat," board spokesperson Doug Hadley tells CBC News.

Right now, Citadel High School gets steam heat piped underground from a nearby hospital to the school, but the system suffered failures in 2008, 2009 and 2012.

"It’s where it’s located,” Hadley said. “It’s a very wet marshy area. As the water seeps into the concrete tunnel, the condensation has caused breakdowns.”

"We're just concerned there is going to be ongoing problems with a steam pipe that is buried underground and is always going to be immersed in water and potentially break down and not deliver steam to the building."

The board expects the province to pay for the natural gas hookup, which it estimates will cost several hundred thousand dollars. In December 2012, the Dexter government announced a program to pay for school conversions to natural gas.

Despite the board criticism, the Nova Scotia Department of Transportation and Infrastructure Renewal says it’s working fine.

"We have confidence in the steam heating system there. It’s green. It’s cost effective," transportation spokesperson Pam Menchenton said.

Last year, the school board paid the Capital Health Authority $130,000 for the steam heat delivered from its steam plant at the Halifax Infirmary site.

Capital Health spokesman John Gillis was unaware of any recent problems beyond a single day last year.

“In March 2012, at the school’s request, the supply was stopped to enable some repairs at their end," Gillis said in a statement to CBC News.

The board wants Citadel hooked up by September 2014.