This is approximately where the head will go the elbow is the outlet to the outlet sea cock and the the barb on the motor the inlet from the just below the sea strainer in the engine bay photo below


sea water level is just under the the bottom of the sea strainer which in the head photo would be at the macerator motor level
I intend to fit a a s/s T where the barrel fitting is and run a s/s pipe across into the head compartment through the fiberglass wall and then fit a ball valve for the inlet side of the head
The out let sea cock would be below and to side of the head in the direction of the elbow is pointing to a new hull through sea cock .
My question is .Should I fit a vented loop. on either or both inlet and out let hoses
I may fit a holding tank later .

Thinking about it a little longer I think I better vent both sides if used and left open while sailing I might run into a problem
So I'll sort it out and probably alter how the the macerator and inlet and out let of the head again


Answered my own question
I think Ill run a inlet vent at the inlet ball valve on the head compartment side of the engine bay wall and the out let on that rear head compartment bulk head