Furnace Covers

Protect your water heater and furnace while your RV is in storage. Simple but effective vent screens keep out mud daubers, wasps, mice and birds. Easy installation instructions and tool included. Durable stainless steel won't rust. NOTE: Remove while appliance is in use.

I got mine from Camping World, but most RV supply places carry them. Make sure you get the correct one for your furnace/hot water heater.