Drsafety, that isn't as safe as getting an aqua door, which in turn isn't as safe as draining. Still, it can work well enough in mild climates. The idea is to have defense in depth, which is to say several different things that each individually prevent damage. That way, even if one of them fails there are still other things protecting you. For more northerly climates you want a jug or gizmo, plus an aqua door or draining, plus anti-freeze. That gives you three things which can each individually prevent damage.