Black Water backing up in shower when driving.

There is something wrong with your plumbing. Water (or effluent) will find its own level in the entire system. To back up in the sink - which is no doubt at least 2 feet higher than the shower - would require the shower to be 2 feet deep in effluent. This would be more than inconvenient.

Both shower and sink should have traps, and the tank should be vented. If the backup you got was a small amount, it is possible that the vent is plugged (birds, wasps, bad construction) and the tank pressurized by a warming day, this could force the material in the traps up into the bowl and shower pan. To see the actual level of the black tank, hold the toilet flush open, on most RV's you will be able to see directly to the surface of the effluent.

Next time, don't turn it over and shake.

Sorry, devil made me say it.

If you are going that route, maybe a couple soft rubber balls just big enough to insert into the drain, with fender washers top and bottom and a bolt through it you can tighten to squash the ball so that it doesn't dislodge. Stick one in each drain, tighten the bolt a bit, and you have a sealing stopper.

I can't imagine the sink overflowing. to do so the shower must have been under 1 1/2 ft of water.???
bumpy

If you can get to the shower drain plumbing, a long term solution may be to put a ball valve on the shower drain. That'll prevent backwash when on the road. Just remember to open it when you shower.

If you can't easily get to the shower drain plumbing... never mind.

If you can remove the drain cover, you can install a mechanical plug made by Cherne. Whether your drain is 2" or 1-1/2", I don't know. Either way, just buy the right sized plug -- probably $4.00 or so.

Bruce

Kayteg1 wrote:
I bet your tank vent pipe is inserted several inches into the tank, therefore not allowing you use full tank capacity.
Common fix is known as harpooning. If you can see vent pipe via drain pipe, you can attach saw blade to a pole and cut the long pipe short.

I'll check when we get back this weekend. Thanks.

For now I have the "cork" type for the sink, and the flat type for the shower floor drain. Toilet, bathroom sink, and shower, sit right over the main drain line. I was really surprised it made it all the the bathroom sink. Shower I could kind of understand. It may have had just the wrong amount of fluid in it to cause this problem, because we have used it several times without this issue, and drove with waste water in tank.

Peg Leg wrote:
Flat rubber stopper over drain with a weight on top?

I would go the route of pulling out the plastic water stops that don't really seal well during a "back-up" situation and use black rubber "corks" that are inserted into the top of the drain and forced in. Should hold until you can figure out why it is backing up. I believe the big box hardware stores should have those stoppers in the plumbing section.

I bet your tank vent pipe is inserted several inches into the tank, therefore not allowing you use full tank capacity.
Common fix is known as harpooning. If you can see vent pipe via drain pipe, you can attach saw blade to a pole and cut the long pipe short.

Peg Leg wrote:
Flat rubber stopper over drain with a weight on top?

I bought some at Home Depot yesterday:). I really would like a little better fix though.

This is only about a 30 mile trip from my house to a small lake in a National Park were I go to camp/kayak. No dump stations available along the way.