Gray water tank traps and vents

[jkxtreme]

We have a 3901 RK which has 2 gray water tanks: one for the kitchen and one for the main bathroom and laundry. We're seeing the 2 sinks, shower, and washing machine are draining VERY slowly.
Is there a single plumbing trap for the 4 drain points or are there multiple plumbing traps.
If each drain point has its own trap then I need to know where the vent is for the tank because I might have a vent issue.
Since I don't see a trap under the sink vanity, I'm guessing there is a common trap for the 4 drain points.
Assuming I have a clogged trap, what's the best way to open it. I've heard baking soda / vinegar. Any other suggestion?

[rohrmann]

You might have these in place of actual vents up through the roof. https://www.trekwood.com/products/15...-1-2-w-Adapter
You still might have conventional P traps, but they should still be visible. https://www.trekwood.com/products/15...-w-Flanged-Arm
There is another device that is used in place of the P trap that could be causing slow draining. These use a flexible membrane that closes off when water is not draining to keep gases from getting into the rig from the tanks. https://www.trekwood.com/products/15...embly-Uniguard

[jkxtreme]

I don't see any p-traps under the sink in the main bathroom. Under the sink in the half bath I do see a p-trap so that sink likely drains into the front black tank.
Do you know if I can use Drano to clean out the lines.

[jkxtreme]

I see one of those mechanical devices under the bathroom sinks. I wonder if there is one of those on the shower too. I can't believe they would install 3 of those but who knows.

[Carl n Susan]

The shower will have a HepvOo valve under the floor. You will have to remove the back wall of the pass through (depending on where your shower is in the RV) to see it.





I am not a fan of Draino or any other caustic drain cleaner in the RV, here is what the manufacturer says about it:


How to clean a HepvO valve?

No routine or seasonal maintenance is required for the HepvO sanitary waste valve, however, should you blow-out your drainage lines do not exceed 80-100 psi. HepvO is resistant to standard caustic-based drain cleaners. It is also resistant to acid-based cleaners with concentrations up to 10%.

[rohrmann]

Like Carl said, Draino isn't needed in these rigs. Our rigs used the Hepvo devices, which it looks like they are using a different brand of the same style of device, this made by Lasalle-Bristol called Uniguard. DO NOT poke anything down the drain into one of these things with the membrane in them or you will definitely be replacing them. Our rig has two vanity sinks, one has a P trap and the other has the Hepvo device, and vertically under the shower there is another Hepvo device. They work well, but do occasionally need to be cleaned, and if removed, you must get them oriented correctly so they work properly.

[jkxtreme]

You are all going to get a good laugh out of this... The problem was the gray tank was full. We thought we had emptied it but we have an additional gate valve at the end of the drain pipe that we had forgotten to open. So when we pulled the factory gate valve we didn't pay attention to the flow so we didn't realize nothing was coming out. Once we realized our mistake it only took a minute to fix the issue.
Thanks for all of the replies ... we did get an education. We removed an inspected the 2 waterless p-traps and removed covers to see where the piping ran so I guess all the time was not in vain.

[beeje]

You figured it out before I could answer. I was going to say a lot of units have waste valves that people either forget about or simply never knew were there