Step 1 - Drain Tanks:
In this photo I have drained the port and starboard water tanks with the fresh water pump & then disconnected them from the manifold, via the "Shark Bite" PEX tube fittings, so they can drain into the bilge compartment, naturally & through gravity, with the rocking motion of the boat.
This photo was taken after only a few hours and it was almost totally drip free and dry at this point. This means both tanks have virtually zero water in them and will get NO antifreeze.. I prefer not to put any antifreeze into my tanks because it is a bear to get out through the process of dilution in the spring.
I'm rather uptight about keeping a dry bilge, mold allergies, that's why you'll notice a rubber stopper in the limber hole to keep the water contained in that compartment.