Originally Posted by mike d.
You should never piggy back on your engine water
intake! Nor is it a good idea to run discharge through and intake. If you giggy back your intake you stand the chance of causing the engine intake to get air bound.
I agree completely with Mike, especially when it comes to ANY thru-hull sharing both discharge and intake. Not only do you not want to risk pulling any galley
waste into your engine, you don't want to pull it into the toilet either...not only can that create a blockage in the intake line, pump and/or the channel in the rim of bowl--any of which can be a real PITA to clean out--it will STINK as it rots and decays even if it doesn't block the intake.
It's less risky to use the same thru-hull for the toilet and engine water intake, but still not a good idea 'cuz it's not uncommon for the toilet to suck in animal or vegetable sea life that can block or seriously reduce the flow of water to the toilet AND the engine. A strainer would keep anything out of the toilet and the engine, but also block the flow of water to both.
I'm hoping that what you called a "brass" seacock is really bronze, 'cuz brass isn't durable enough to be used for seacocks.