A more modern method is to use two discharge outlets in the holding tank..
One hooked direct to the deck fitting the other to the lectra san or direct to overboard discharge.
AS almost all the poop pump problems I have had come from the unit drying out and paper holding the suction valve open just a tiny bit , I would have a tank built with a bottom drain hookup .
A Dupree valve would allow the tank to be closed and the pump removed if required.
Manual Valve and Parts - Dupree Products
https://www.
dupreeproducts.com/SearchResults.asp?Cat=3
Requires disassembly and reuse of
valve gate,end cap, o-rings, spring, ... The Twis-Loc termination system provides a truly durable
sewer hose connection.