Type of tank?
I am not sure what you have in your H30, but in my H33 I have a 6(?) gallon round tank. Very similar to a minature H.W. tank found in you home. It might even be the type used in RVs. Anyway, it has a drain towards the bottom where you can attach a garden hose. After pumping out by opening the hot and cold water taps, I disconnected the input hose and output hose from the H.W. tank, and spice them together with a plastic hose-spicer. I then attach a garden hose to the H.W. tank drain, open, and drain all the water out of the tank. When I then add pink antifreeze to the fresh water tank and pump it through the system, all lines are used until pink comes out of the faucets. The H.W. tank stays empty of water and antifreeze. My theory is that if there is a little water left in the tank, so what? The resulting ice has plenty of room to expand, and nothing is damaged. This has worked for over 20 years on this boat here in Rochester, NY.Ken Palmer, S/V Liberty