On my previous boat which wintered ashore I drained the water tank, but not to let the water go to waste I connected the tank outlet to the engine and ran the engine. This emptied the tank and flushed the engine of salt water at the same time.
On my current boat which winters afloat, I have never (eleven years) drained the fresh water as it gets used when I am on-board (river mooring, no shore power).