Just wondering..I have a stainless chimney liner that is currently hooked to my oil fired boiler. We are planning to take out the oil boiler and replace it with the new Acadia heat pump in another location. For hot water, I would like to install an "on demand" propane tankless water heater.Can this heater be vented through the stainless liner, or does propane have to vent through aluminum? Thanks for any reply.