question

Rob66

What problems will you have if your expansion tank has no water in it (system full no air, expansion tank drained)

Dan M_6

It might not be empty

If you drained the tank and then put pressure, by adding water or opening the tank isolating valve, to the system the tank will have some water in it. When the water warms up and expands to operating temp it will further fill the tank. Usually those tanks are generally filled half way. In the worst case if there is not enough water in the tank, air could be displaced into the system.

Rob66

Thanks

OK

Thanks