Hi,
May I add a comment? The previous owner of Alchemist once gave me a tour of his toilet plumbing. I compared it to my holding tank in my P275, also in the bows, forward of the sail bath.
Unlike Alchemist, my boat has a valve next to the toilet to select 🅰 pump out toilet to sea or 🅱 pump toilet to holding tank, or [c] pump out holding tank. You may be interested in an alternative. With a view to reducing the number of connections that can go wrong, Alchemist's toilet always pumps out to the holding tank, via a regular pump. Then changing a diverter valve changes the pump action to pump out the holding tank. This seems wonderfully simple.
Cheers-Ken
Ken Surplice
Vice Commodore