Gray water drainage design help (see drawing)

DutchmenSport wrote:
Even with your revised plan, the tanks themselves need to be vented, otherwise you've created a vacuum in them. If you don't have the sink tank open and draining, and the bilge pump is running, after the sink tank pressurizes, you'll start having water shoot out that vent. If there was no water in the p-trap in the sink, then the p-trap would serve as a vent. The vent needs to be just higher than the drain, that's all, but going to the actual tank so as it fills with fluid, the air can escape.

Reason why I said the pump would be a PITA, as stated above.... power failure, clogs, running your battery down, potential leaks. And how do you drain that system once the heat is turned off in the camper if you're not using it and temps get below freezing? Can you remove the bilge pump and winterize it? I suppose you can pour a couple gallons of "pink stuff" down the shower and feed it through the system, that would winterize it.

Ok that makes sens, I took the P trap out to directly vent the tank outside. The tank that the bilge pump sits in has no cover since the water will only go back in the shower pan if the bilge pump stops pumping.

I will try to take another look at the van inside and out to find a spot I could add a second tank underneath the shower but the big gas tank and propane tank are right underneath...