Originally Posted by skipmac
Have not installed it yet but this is pretty close to what I have designed for my boat. Main difference is the holding tank
will be behind and above the vanity but drain out the bottom, waste in on the top.
So how was the pump out rigged? I'm planning to put a Y-valve on the single
bottom drain line which will switch between the thru-hull and the deck
pump out and trying to think if there is any reason why not to do it this way, other than problems with the valve (but I'm using the Peg Hall recommended, never fail valve).
I should think that would work just fine. Some have put in a separate line to the tank so there's no need for a Y-valve, but I like that a y-valve allows you clear the gravity feed line.
You could even just use a T-fitting above the seacock. If you have the seacock closed, there's really no reason for a y-valve. The pump out will go directly to the tank. A Y-valve would prevent any sewage from running up the pump out hose when heeled to that side. Another alternative if the seacock isn't easy to reach is to place a ball valve on the bottom of the tank - just open that to drain - again, you could just use a t-fitting below that, with no need for a y-valve. This would allow raw water
to flow part way up the pump out line, but so what? - just helps keeps it clean.
What I did to keep head
repair simple was to just buy spare pump assembly for $70. No need to muck about with flapper valves, etc. on the spot, - just swap a whole new pump and rebuild
the old one later if desired. With no sewage pump the pump on the head
itself is about the only thing that can fail - have a spare pump and it keeps repair very simple.