97 Coachmen Catalina Plumbing Problem

[howardmcc]

I recently bought a 97 Coachmen Catalina and on our first trip I used the bathroom sink and noticed that as I ran the water it would come up in the shower and until I turned it of it kept filling up. Since that time I have tried four different things:

1. Used a RV safe drain cleaner, which did nothing.
2. Used a plunger to clear the line and nothing changed.
3. Used a 25' hand auger and snaked the shower drain, bathroom sink drain and nothing changed.
4. I used the same drain snake and ran it down both of the vents and nothing changed.

 

Before taking the above steps I made sure that the gray water tank was empty and I checked to see if there was any clean outs and there are none.

 

I worked as a plumber many years ago and I have never been faced with this problem or anything like it. Has anyone had this same problem in the past? If so, how did you fix it, what did you find and what should I be looking for? I am open to all suggestions? We are taking off on a 5k trip west in 19 days and would like to resolve the problem. Any help or suggestions?

[Kirk W]

First, welcome to the forums! Helping is what we do so here is my best shot on this one.

 

I am a bit suspicious of the way that the RV is plumbed as the cause of this problem, but am only guessing as you clearly have more plumbing experience than I. Have you traced the drain line from the sink to see just how it is routed? Am I correct it gathering that once you turn the water off in the sink, the shower pan then drains out normally? Have you tried using the shower to see how it drains?

 

I'm wondering if the shower and the sink might be sharing a "P" trap with the sink draining into the line just below the shower outlet and above that "P" trap? It may also be that the line from the shower has no slope and so it drains slowly?