pump or gravity for off-shore blackwater?

[subdude]

I'm sure this discussion is in CF archives somewhere; I just can't find it.

On our C&C, the black water tank is under the v-berth, slightly above the Y-valve with a vented line to the deck and thru-hull respectively. The previous owner had purchased a manual whale gusher pump for blackwater and never installed it. It's designed to fit between the Y-valve tank and the thru-hull. As we prepare to head into BC waters (!) increasingly over the next years, I assumed I'd need to install the pump to evacuate the tank where legal.

If gravity does the work, I guess the pump is unneeded, yes? Or would a pump somehow be more effective, faster, etc?

Pete

[boatpoker]

The pump may help pull clogs out where the gravity many not.
Those pumps have to be dismantled periodically for cleaning, not fun.

[peghall]

Your tank's location seems to rule out gravity drain 'cuz for gravity drain to work, the entire tank must be above the boat's waterline...if not, it'll take on water faster than you can dump it when the thru-hull is open.

--Peggie

[wsmurdoch]

When we are in an area where discharge is legal, we choose our time and place to minimize our inconvenience to others. Our head always goes into the holding tank, and the hand pump lets us quickly and totally empty the holding tank (with a following sea water flush from the toilet and through the tank and pump) when we are in a tidal area, outside a harbor, away from swimmers, away from beaches, away from other boats....

[GILow]

Originally Posted by wsmurdoch

When we are in an area where discharge is legal, we choose our time and place to minimize our inconvenience to others. Our head always goes into the holding tank, and the hand pump lets us quickly and totally empty the holding tank (with a following sea water flush from the toilet and through the tank and pump) when we are in a tidal area, outside a harbor, away from swimmers, away from beaches, away from other boats....

^^^^^ This!

Same setup on our current boat and I’m doing the same with the new boat. Eliminate the smelly, leaky Y valve altogether and go straight from the toilet to the holding tank.

Manual pump to empty holding tank (120 strokes on the current boat, takes about two minutes.). I prefer manual pump for reliability. I REALLY don’t like the idea of the pump failing.

But I also add a separate pickup pipe for a deck pump-out fitting. Nice to have in places where there are proper facilities.