Grey water tank won't drain

[RonM]

Long story short, the grey water tank won't drain. I don't feel any difference in the valve and I can get a few galleons out of a full tank, down to the 2/3 full indicator light but then it stops flowing. I tried the liquid dishwasher soap trick this morning with 5 galleons of hot water using the kitchen sink thinking it was just a clogged sensor. I measured the amount of hot water I put in so I could determine (best guess) how much I got out. First indication something was wrong was the full light indicator coming on. If it was just a stuck sensor then 5 gals of water wouldn't ground the "full" sensor so it should have stayed at 2/3 but it didn't. 2nd bad indicator was grey water leaking out the bottom of the trailer onto my driveway. I drove 40+ miles to Camp Pendleton and dumped the grey tank expecting to get a rush of water...I didn't. I checked the indicator lights and it's back to 2/3.

We're very careful about what goes down the drain but checking other RV sites people say this happens to them all the time..news to me. I'm thinking a clogged vent or just normal accumulation over 2 years but how do I find the actual problem and then fix it? We've got another 5 weeks coming up so I gotta get this fixed!

Thanks for your help
Ron

[TCNashville]

Ron, there is a valve in your plumbing and it's called an air admittance valve. If this valve has failed it will prohibit the draining of the grey tank. Kinda like putting your finger on the end of a straw filled with water. All campers have them. Mine is located up under the bathroom sink vertically. Another possibility is that the grey tank is clogged at the exit point. You'll have to do some investigating.

[RonM]

Thanks very much, I've never heard of the air admittance valve before so that's where I'll go first. Hopefully that's as far as I'll need to go.

[SloPoke]

our old motorhome had a similar issue, but with the black tank. It plagued us for a couple of years and sometimes would go away for a year or two and then suddenly be back.

Now this is what happened. When the tank was put in, they cut the hole in the place where they wanted the drain, and that piece fell back into the tank instead of it being taken back out. The drain hole was at the back corner next to the bottom of the tank - so somehow when the black was sloshing, the cutout that fell back into the tank would end up blocking the drain hole on the tank.

It took having a leak at the tank fitting a few years later to discover that the cut-out part was still in the tank, once it was removed... we never had a problem like that again.

[RonM]

Thanks for the feedback. I'm praying we don't have the same issue. Right now I'm focusing on the air admittance valve in both the kitchen and bath sinks. I went in this morning and found both of them and the kitchen is easy with lots of room above the valve. The bathroom sink is almost sitting on the valve so I'm going to be spending some interesting time under the bathroom sink... I'll let everyone know what I found when I get it fixed.

Thanks again, Ron

[TCNashville]

Ron, SloPoke could be on to something here. You might want to check the grey tank vent pipe that vents to the roof. If it has somehow come loose and fallen back into the tank it would produce the same result. Just a thought.

[RonM]

I’m running out of options for the grey water tank problem. Based on feedback from the forum I made sure the AAV’s were working, which they weren’t until I took them off and tapped them on the floor to unstick the small plastic plate inside the valve. I cleaned them and reinstalled the kitchen but not the bathroom. I left the bathroom aav vent pipe completely open and tried to drain the gray tank with no success. I replaced the aav and closed everything up. The “P” traps under both sinks were full so that takes the aav’s out of the problem.
I drilled a hole in the floor so I could see the top of the grey tank where the vent tube is attached. The top of the tank was dry and the seals appeared to be intact.

One thing I found when checking the aav’s is the plumbing under the kitchen sink wasn’t fully connected. Half of the “P” trap wasn’t connected at all, just sitting there, held in place by the one fitting that was actually connected.

Here’s what I’m down too:
1. Something is blocking the drain from inside the tank because the vents aren’t the problem and I don’t think there’s anything else in the flow line to stop the flow. Slopoke had this issue with his tank.

2. The water that leaked out of the tank in my driveway was from ether a hole in the top of the tank or considering the other plumbing issues, a disconnected fitting. Neither of which explain why the tank isn’t draining in the first place.

Am I missing something? I really don’t want to cut the barrier under the trailer to look at the tank directly but I think that’s where I’m headed unless someone has a better idea.

Is there a way to force water into the grey tank from the dump valve line?

Thanks very much,
Ron

[Merrick]

Flush King hooks onto the drain valve and forces water up into the tank. Maybe that would work temporarily.

[RonM]

Thanks for your help. I'm going to try that next and hopefully I won't need "high Pressure" water for this to work.


I just watched a youtbue video on 4 of the best pressure water rinse systems and it turns out none of the external systems i.e. king flush, sewer solutions or one other I don't remember right now only work if you have a straight shot from the tank to the end of the dump valve. Almost no one has that. Even a single 45 degree turn is enough to block the pressure driven water from reaching the tank. King flush was the best of the three external systems they showed because it has a blade valve to allow the water to accumulate in the tank instead of turning around an going right down the drain without ever reaching the tank at all. Even with the King FLush the water doesnt have any pressure left when it reached the tank but it is flowing from the opposite direction which might be enough to get the job done. In the interest of full disclosure I bought the "Sewer Solution" kit yesterday on amazon and it was the least effective of all 4 they tested.

[sciencenerd]

Originally Posted by RonM

Thanks for your help. I'm going to try that next and hopefully I won't need "high Pressure" water for this to work.


I just watched a youtbue video on 4 of the best pressure water rinse systems and it turns out none of the external systems i.e. king flush, sewer solutions or one other I don't remember right now only work if you have a straight shot from the tank to the end of the dump valve. Almost no one has that. Even a single 45 degree turn is enough to block the pressure driven water from reaching the tank. King flush was the best of the three external systems they showed because it has a blade valve to allow the water to accumulate in the tank instead of turning around an going right down the drain without ever reaching the tank at all. Even with the King FLush the water doesnt have any pressure left when it reached the tank but it is flowing from the opposite direction which might be enough to get the job done. In the interest of full disclosure I bought the "Sewer Solution" kit yesterday on amazon and it was the least effective of all 4 they tested.

Could you use a snake to go in from the drain opening, going through the open blade valve and into the grey tank? That may push in any obstruction, if there is one.

[RonM]

I think I can but I'm not sure how to set it up. If the snake works and my grey tank is 2/3 full like the indicator light says I could have one hell of a mess to clean up! Not to mention the bath I might take in the process... I still think it's a valid recommendation and something have to figure out before I cut the barrier.

[RogerR]

You might consider buying or renting an endoscope which is a tiny camera and led light on the end of a few feet of soft wire. I had a house plumbing problem and found it I taped it to a stiffish hose I could make it go around curves. Then I could turn on water to rinse as I went as needed.

USB Endoscope, DEPSTECH 2 in 1 Semi-Rigid Borescope Inspection Camera

Solid Brass Hose Jet Sweeper Nozzle ~ Made in USA ~ with Extra Washers

endoscope plugs into your laptop or tablet.
I have also used it to look into walls to find what was back there with only a 1/4 inch hole.

[RonM]

Great idea! I just bought one on amazon for $20.00. It should be here day after tomorrow and I'll let you know what happens.

Thanks to everyone that responded. Several great idea that I would never have thought of.

[TCNashville]

Yeah please keep us posted. If the AAV's are operational and the vent stack is clean it has to be clogged at the gate valve. One question, is the underbelly covered on your camper? Here's a really wild theory for you. If the grey tank has shifted due to a broken strap and is leaning back it won't drain. I know, a shot in the dark. Good luck.

[RonM]

I don't know the answer to that yet but I will once the camera shows up. If the camera works the way I expect it to (and i'm a camera guy from way back) at the very least I should get a better idea of what I'm up against. The best part is I can do all this with a small hole or two in the under belly and not a gash big enough to crawl into!

[RonM]

If anyone is interested this is what I got from amazon for $21.00: If it works it might be something others might be interested in.
USB Endoscope Inspection Borescopes - RonaLOC 3 in 1 Semi Rigid 720P HD with 5.5mm Waterproof Snake Camera, 6 Adjustable Led for Android Smart Phone, MacBook, Windows PC (16.4 FT)[/B]

[Route 66 Traveler]

Originally Posted by sciencenerd

Could you use a snake to go in from the drain opening, going through the open blade valve and into the grey tank? That may push in any obstruction, if there is one.

That’s exactly what I did when my grey water only came out in a trickle. When I inserted the snake the volume increased a bit, and a few more wiggles with the snake and I had a gush of water coming out. Along with the water came the small, round cut out piece from the tank. When they drilled out the tank they just let that piece fall into the tank...the guy that did it probably had a smile on his face knowing it would cause somebody grief. Never had anymore problems draining the tank.

[TCNashville]

Right after I bought my camper I looked down into the black tank and pulled out 2 or 3 large pieces of construction debris. Glad I checked first before using it.

[wags999]

I don't see what RV you have, but some RV's have 2 grey tanks. You may be draining one, when it's the other one that is full. Do you have a rear Kitchen? If so you may have one tank for the kitchen and another tank for the bath and kitchen.


Just a guess... good luck

[Fyouberg]

X2 on the snake application. It’s just greywater right? Even if your endoscope does spot a blockage, this is going to be nessessary right?