Yes, again, but with a twist. I understand that plugging of the overboard drain line while the valve is closed is the biggest problem with this type of installation. It so happens that our boat had an electric macerator type head on board when we bought it. I'm thinking of plumbing the head discharge to a tee in the holding tank overboard drain line, with a valve between the tee and the tank, and retaining (of course) the thru-hull valve downstream of the tee. The thought process is that if (when) the drain line plugs, I can use the head discharge pressure to blow it out by closing one valve at a time and running the head. I don't really think a plug would be so solid that I'd be risking blowing a hose off a fitting or anything. I would have a dip tube from the top of the tank for pumpouts.
Does this sound workable?
Does this sound workable?