Slow draining gray tank . . .

[Ranger413]

I'm dealing with a slow draining main gray tank on my 2021 4113. Every once in awhile it will woosh empty as it should. I'm also not sure if I'm getting a complete empty or not.

I first tried some remedies to address food and sludge buildup - boiling water, baking soda and vinegar and dishwasher detergent. No luck with those three separate solutions.

I also purchased one of the clear elbows with a hose connection. Using a Valterra gate valve downstream of the elbow, I was able to backfill the gray tank and flush it several times. Seems to drain fine that way most of the time.

I believe I'm down to a bad vent or an obstruction in the tank (thinking a slug of plastic from when they drilled the tank out). Checking the vent seems like the logical first step. I only have one vent on the roof up front and assume that one is the black tank. For the gray tank am I looking for one of those capped valves (air admittance valve) somewhere in the underbelly? Any help would be appreciated.

[JDsRVcrzy]

Have you tried pouring a bag off ice down the tank and immediately follow it by a drive with the trailer. The ice will hopefully break up what you have in the tank that's causing your issue.

I had used one of those alleged disposable black tank deodorants treatments and the lining got stuck on my fill sensors. No matter what I did, (trailer's build in flush/top wash wand) it would not clear until I did the ice method..

Good luck!

[Grumpy]

Originally Posted by Ranger413

For the gray tank am I looking for one of those capped valves (air admittance valve) somewhere in the underbelly? Any help would be appreciated.

That will not be in the underbelly, but in the cabinet under the sinks.

[Route 66 Traveler]

Originally Posted by Ranger413

an obstruction in the tank (thinking a slug of plastic from when they drilled the tank out).

That’s what my problem was. Mine had a straight drain pipe and I was able to remove it using a long wire. Mine would take about 10 minutes to drain 5 gallons.

[Ranger413]

Originally Posted by Grumpy

That will not be in the underbelly, but in the cabinet under the sinks.

Correct:

I traced the vent lines from both the black and gray tanks. They go up the wall just to the right of the stove behind the kitchen cabinets. I am not able to see the pipes above the base cabinets. I tried running a camera up the wall to see if the gray line tops out or if the two pipes merge before the roof. Unfortunately, my camera wouldn't track up the pipes far enough to see.

[TaftCoach]

You're at the point I would stop and post here. So I'm just wishing you good fortune on finding the problem.

[Ogerjohn]

I would think an obstruction, since it changes when you backfill. the vent would make the drains gurgle when it is struggling to replace the fluid with air.

[Ranger413]

Originally Posted by Ogerjohn

I would think an obstruction, since it changes when you backfill. the vent would make the drains gurgle when it is struggling to replace the fluid with air.

I do get the gurgling when the tank drains slow. Other times, like when we have water in the shower or the sink (full tank), we get a good drain. It varies though, sometimes it'll be a whoosh with a lot of rumbling. Other times, what would look like a normal (medium flow) drain.

I saw a video where a guy located his gray tank air admittance valve behind a wall. He ended up extending the pipe up to the roof where he installed a traditional roof vent. Since I lost sight of the gray tank vent behind my kitchen cabinets, I wouldn't be surprised if this was my situation. Either that, or the gray tank vent has to join with the black tank vent before the roof, which I think would be a no no.

[Ogerjohn]

Originally Posted by Ranger413

I do get the gurgling when the tank drains slow. Other times, like when we have water in the shower or the sink (full tank), we get a good drain. It varies though, sometimes it'll be a whoosh with a lot of rumbling. Other times, what would look like a normal (medium flow) drain.

I saw a video where a guy located his gray tank air admittance valve behind a wall. He ended up extending the pipe up to the roof where he installed a traditional roof vent. Since I lost sight of the gray tank vent behind my kitchen cabinets, I wouldn't be surprised if this was my situation. Either that, or the gray tank vent has to join with the black tank vent before the roof, which I think would be a no no.

Just remember that they are not necessarily built to building code. I would check the roof for the vent. I would think there is one for each tank through a wall to the roof. You might be able to contact Jayco about if they have a plumbing diagram as to where and what is thins are located.

[TWP723]

I realized on my Montana, I have to literally lean it to the DS to fully drain the tank. I don't know if the tank is mounted weird or what but noticed a dramatic difference in the draining. I have a clear elbow at the drain and as soon as I leaned it to the DS, it gushed out.