Propane leak drain valve?

My ski house has a drain pain (galvanized steel, about 4″ high) to drain propane to the outside (though a 4″ PVC pipe) if there’s a propane leak. Unfortunately, that leaves a 4″ pipe that is open to the outside.
Is there any way I can keep the safety of having the drain without letting the cold air in?
Replies
back draft damper (check valve)
Your propane tank is inside?? Or are you talking about a pan under an appliance?
I've heard of drain pans for water heaters and washing machines, but not for propane. That doesn't mean they don't exist, but propane is a vapor and it's hard to imagine it cooperating and letting itself out thru a vent pipe, especially if it has to push open a damper to do so (dampers are fine for a pressurized vent such as a dryer, and motorized dampers that open a vent when an appliance is firing are also typical). Propane is heavier than air and pools on the floor looking for a way to go downhill, and I'm pretty sure that any significant leak in the house will result in propane that does not stay in the pan and does not go outside thru a vent.
The best thing you can do is to have your propane supplier come out and take a look. Or, have a mechanical company do it.