Bathroom flood - What did I do wrong?

dougrainer wrote:

Dutch_12078 wrote:

dougrainer wrote:

Dutch_12078 wrote:
Bathroom sinks are sometimes plumbed to drain into the black tank, likely to help balance the capacities. My last two motorhomes have been plumbed that way. The RVIA standards permit one device besides the toilet to drain into the black tank, but the shower is not normally used because of the higher backup risk.

The ONLY reason that any Gray source may go to a Black tank is because the floorplan design of the RV keeps that particular Gray source from going to the Gray tank. Doug

With all due respect, Doug, that's not always the case. The bathroom sink drain in my current Coachmen for instance, has an elbow that's just above the grey tank that directs the drain to the black tank about a 18" away. The drain could very easily, if not more easily, have gone straight into the gray tank.

I have been in the RV business 40 years. 5 building them and 34 as a tech. ALL Gray water will go to the Gray tank if it can. If it cannot, then they will plumb to the Black tank. That said, I HAVE over the years replumbed Gray from the Black because the factory plumbed a Gray to Black when there was adequate slope and a way to route to the Gray tank. But as I stated, IF the Gray can be routed to the gray tank, all will be routed there. Doug

I won't argue with your experience, Doug, but there are no signs that my Coachmen's drain plumbing has ever been modified from the factory installation. I actually do prefer having the bath sink go into the black tank though, since it helps balance the two tank capacities. My Allegro Bay, on the other hand, had been modified with a 3" connector pipe tying the two tanks together, making them functionally one large tank. I don't recall where the bath sink drained on that one, not that it made any difference.