A replacement water heater from Atwood is $455. Atwood 10 gallon Water Heater LP Gas DSI - $455.09
Someone is digging deep into your wallet
Also from good Sam ESP WATER HEATER/BOILER ASSEMBLY - Covers all parts.
I think you should be covered. Post this on RV.net and for sure Good Sam will get back to you about this
In exclusions though it says: Any damage or failure resulting from rust, corrosion or freezing