I realize this is an old post, but I haven't been able to catch you on your boat.
I would really like to hear more about where the 30 gal of water may be located.
The old maintenance log for Night Watch mentions the removal of the "3rd bilge pump" w/o mentioning the location.
My shower drains into the area directly into the bilge that ends up in the bilge (directly below where the heat exchangers are on the engine). There is a bilge pump there that is wired to the "sump pump" breaker, so I manually turn it on to shower. I remember you have better access to this area as I have 4 batteries sitting on the shelf above the bilge.
I also have the auxiliary pump in the stair by the lower helm and main bilge in galley. When I first got the boat one of the dock people mentioned I had water in the keel, but he would not share more information, so I have been looking for where he saw it ever since.