My shower is not draining and I suspect there is a venting problem. No other water drains are having a problem. I've confirmed that the tank is empty and there is no blockage. If I open the grey tank it creates a vent and then the shower will drain.
I see two of those black vent caps behind the washer/dryer is one of those for the shower or should I be looking somewhere else? I don't see that the pipes behind the washer/dryer are attached to go to the shower area.
Any help would be appreciated.
Check on the roof. At least on earlier coaches the tank vents are on the roof, not inside the coach.
It is possible that the PVC pipe to the roof has fallen down into the tank/below level of fluid in the tank so it will not act as a vent.
On our 2003 U320, there are 5 air admitance valves (the ones you pictured).
The two behind the washer are both for the washer on our rig. One by kitchen sink, one by bath sink, one by shower (on our rig, in the hamper behind the toilet).
Try and figure out where the drain line runs from your shower, and there will be a AAV on that line.
In addition, on our rig, there is one roof vent that is for both the black tank and grey tank. One roof vent serves both.
That is how our 2003 is set up, yours may vary.
Well that's sort of good news that I don't have to remove stackable washer / dryer. However, my shower is on the driver side adjacent to the washer dryer and the toilet is on the passenger side. Now I have to see how I get behind the toilet to look.
Your coach could be different. Here is a thread about mine.
Sewer Odor, roof sewer vent, air admitance valves inside... (https://www.foreforums.com/index.php?topic=34106.msg312768#msg312768)
Those black capped vets are vacuum breaks to keep the flowing water from sucking the trap dry. There is a roof vent to allow air to flow in and out of the tank as necessary. As others have said look there. "I" would run a hose into that roof vent and make sure it's clear.
Yes, using a hose or bucket to pour water down the vent will prove that it is not blocked. But, the pipe could still have fallen below the liquid level and NOT able to serve as a vent.
I would blow air down the vent to verify that the pipe has not fallen below liquid level in the tank. If someone by the wet bay hears air hissing down there, all is well. If they hear it blowing bubbles in the liquid-- not so much.
If the roof vent was the issue wouldn't all my drains not empty?
The sink drains would vent through the tub drain.