Originally Posted by Chuck v
Some large class A coach RVs have heated basements so the water heater is less sensitive to cold weather while occupied over the colder months. But any UNATTENDED unit should have its water system winterized, either by adding RV antifreeze or by completely emptying the plumbing system using compressed air.
I lived full time in my 2007 Tour Master for more than 5 years so did not need to drain my water heater during that period. But there are many on-line check lists like the link below that clearly state to drain the WH and then bypass it before you add the antifreeze...
That makes sense.
I use my air compressor to winterize and hadn't thought of bypassing then adding the antifreeze. I think that would make me concerned about the pipes between the tank and the bypass valves still having some water in them. You would have to count on them all gravity feeding out when you drained the heater tank. That seems like a bad idea in my opinion. One coach I bought had a plastic fitting cracked by freezing between the bypass and the tank.
I understand why that was cracked now. Someone bypassed the tank, added antifreeze, and there was still some water in the bypass line.
I would advise against the practice of bypassing and then adding anti freeze. Doesn't always work.