Bob wrote:
Ok, I have a cabin in the country. Because the propane WH is getting
close to being old, when I'm not going to be there for a week or so I
turn the water inlet valve off and the thermostat to pilot. That way
if it leaks, the water spilled will be limited to 40 gallons.
Anyway, when I turn the water valve back on after a week or two, there
is a good amount of air in the tank and hot water lines. There is no
water around the heater. There is no indication of rust on the tank
burner or tank bottom. I crawled under the cabin and there is no
water spotting on the subfloor, nor water on the vapor barrior.
So I'm puzzled. Where is this air in the tank coming from? I'm
talking about air/water spewing for up to a minute. First thought was
a leak and second thought was volume contraction due to cooling. But
that much???

Bob

Valve is not closing tightly. Air gets in thru faucets, etc..