I would say no, the marcerator doesn't suck and assuming your in saltwater, the water will destroy the pump in a short time
I would disregard this ^^ reply.
1) Yes a Discharge Macerator with 'suck' and discharge the holding tank overboard through the through hull
2) No saltwater won't ruin the discharge pump because it is not pumping water in, it is pumping holding tank contents out.
3) The intake pump for my head that draws in saltwater has worked fine for many years. As is the intake pump that draws in saltwater for my air conditioning. The one that draws in saltwater to cool my heat exchanger is also fine with saltwater.
4) You don't need the vented loop, but it will break the vacuum and allow the contents from the vent to the hull drain out. There is no vented loop on my system. Through hull directly below the pump with no loop. No problems.
5) If you place the pump 'downstream' of the vented loop, the pump will suck air. The vented loop allows air into the system, but not out of it. There is a check valve in the vent. The pump will not be able to create vacuum if you place a pump after the vented loop.
