I recently purchased a 1980 Hunter 33. My problem is that the shower drain still has the antifreeze from the winter storage sloshing around. How do I get this todrain out and where does it drain to? I don't believe it drains into the bilge so does it drain into the holding tank? I have not tried using the head yet because I wanted to get this resolved first. The owners manual really has little info about this topic.Thanks!