I have a 2005 268SS that has a seacock closed or a fresh water pipe clogged that is used to provide lake water to my Jabsco manual pump type toilet. I can not find easy access to the holding tank and plumbing area behind and under the head. The only thing I can see to gain access is saw a hole in the plywood/fiberglass panel dividing the lower back part of the head with the backside of the underseat front storage on the port side. Anyone have a suggestion? Thanks.....