To use a metal plug in your Atwood water heater its best to use brass
that could set into the drain for ever and never rust or corrode.
The atwood needs an anode why not replace the other metal plug with
an zinc anode that comes in a brass bushing and a drain petcock,
Atwoods need anodes too, their tank is alumimun and the anode for the suburban water heaters are alumimun, its to bad the tank is nothing but an anode, I love my zinc drainable anode very long lasting been two years and not ready yet