For our old ws43 we installed old fashioned plastic water
tank(new one of course) above the head
. The head
was set on top of a holding tank
. Other than having to open the head/holding tank hole(lever), visitors could use the facilities like shore side folks do. Pull the chain. The holding tank
had two outlets: marina pumpout side and ocean dump side. Ocean dump side was just below the water
line. If you wanted to empty the tank at sea(horrors), just open the ocean outlet(2") and let gravity and the movement of the boat suck the tank almost dry. No muss, no fuss, no odors(except if you were a fish), and no worries about the toilet flooding the boat.
We used fresh water to fill the top water tank to avoid the smell of stagnant sea water. 3 gallons capacity, good for two flushes. Filled with an additional faucet attachment to the regular cold water line. Vent was routed through the hull
at almost deck
level. Outside of manually turning on and off the refill water, was a no brainer system.