RESOLVED: Help .. I'm Baffled !! (black tank not draining)

We have a '16 LM Newport, 1-1/2 baths .. cpl hrs ago, DW says, "Hey, the toilet's full, you need to drain the tank!" Puzzled, I responded, I just emptied the tanks on Sunday!" .. But, went out and pulled the front bath blank tank valve anyway, and monitored the sewer hose!! It flowed normally for maybe 20-30 sec, then slowed to nothing, which I kinda expected .. Went back in and asked what she meant by "the toilet's full" .. she said, "come here and look!" .. The toilet bowl was full of water, stepped on the foot lever, nothing happened. I then, retrieved a short 7' piece of hose that I've used once before .. worked the entire length of the hose down the toilet, expecting it to clear any obstruction stuck in there .. nothing happened ???? What the ****'s going on !!!! .. Went back outside, reopened the black tank valve, a little bit flowed, put water into the flush tank line .. NO water making its way to the sewer hose!! Now, I'm really baffled, the toilet still has a bowl full of water and nothing seems to be draining out !!!??? Anyone have any ideas bout what going on???? HELP !!!!

Re: Help .. I'm Baffled !!

Assuming the valve handle feels normal (indicating that the valve is actually opening and closing normally), I'd guess you have a clog at the outlet of the black tank and the tank didn't drain completely on Sunday. A little fluid appears to be getting through the clog, as evidence by the limited flow earlier today.

If you have a sewer outlet clear adapter with a backflush fitting, you could hook up a hose and push a limited amount of water backward to move the clog. But if the toilet isn't draining, the tank may already be pretty full. So any additional water is going to put pressure on the toilet and possibly force water up the vent, and possibly out over the roof.

If you don't have an adapter with backflush fitting, you can try draining some gray water into the sewer hose while holding it up higher than the bottom of the gray tank. Once you have a few gallons of water in the hose, close the gray and open the black, still holding the hose high. Try lowering and raising the hose to get water moving in the hose and sewer line. With a bit of luck, the clog will move a little, allowing more water to drain. Repeat as many times as necessary to get the tank emptied and running freely.

Then get a clear adapter with backflush fitting.

Re: Help .. I'm Baffled !!

Is it the toilet in the 1/2 bath or the front bath?

Re: Help .. I'm Baffled !!

travlingman said:

Is it the toilet in the 1/2 bath or the front bath?

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in the front bath !!

Re: Help .. I'm Baffled !!

Has it been a long time since you've travelled with any liquid to slosh in the black tank, or have you been full time and stationary for many months/years?

If it is the later, I'm wondering about a a solids pyramid that has sluffed from front to rear of the tank....this could effectively form a poop berm F to R and keep tank semi full on the offside portion from drain hole.

Re: Help .. I'm Baffled !!

LBR said:

Has it been a long time since you've travelled with any liquid to slosh in the black tank, or have you been full time and stationary for many months/years?

Nope !! We're snow birding in AZ, been a month since we left MI, at our resort for 3-1/2 weeks ... Have never had an issue in the 3-1/2 yrs we've had the RV. Everything was normal until noon today!!

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Re: Help .. I'm Baffled !!

"Hi-Viz" Bill said:

Nope !! We're snow birding in AZ, been a month since we left MI, at our resort for 3-1/2 weeks ... Have never had an issue in the 3-1/2 yrs we've had the RV. Everything was normal until noon today!!

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Well, the pyramid buildup theory might be down the drain then.(lol)

Assuming your at an RV park, what if your portion/leg of the park sewer system is plugged/backed up, and slowing/halting your draining process? Possibility??

We were at an RV park in Quartzsite and it happened...sewer leg backed up and up out some drains. Management had to have an all night cleanup performed, limed the areas, then gravel delivered for coverup....s**t happens!

Re: Help .. I'm Baffled !!

Assuming your at an RV park, what if your portion/leg of the park sewer system is plugged/backed up, and slowing/halting your draining process? Possibility??

Great thinking, but once again, No!! The other 3 tanks we have in the RV, are draining fine !!

Re: Help .. I'm Baffled !!

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"Hi-Viz" Bill said:

We have a '16 LM Newport, 1-1/2 baths .. cpl hrs ago, DW says, "Hey, the toilet's full, you need to drain the tank!" Puzzled, I responded, I just emptied the tanks on Sunday!" .. But, went out and pulled the front bath blank tank valve anyway, and monitored the sewer hose!! It flowed normally for maybe 20-30 sec, then slowed to nothing, which I kinda expected .. Went back in and asked what she meant by "the toilet's full" .. she said, "come here and look!" .. The toilet bowl was full of water, stepped on the foot lever, nothing happened. I then, retrieved a short 7' piece of hose that I've used once before .. worked the entire length of the hose down the toilet, expecting it to clear any obstruction stuck in there .. nothing happened ???? What the ****'s going on !!!! .. Went back outside, reopened the black tank valve, a little bit flowed, put water into the flush tank line .. NO water making its way to the sewer hose!! Now, I'm really baffled, the toilet still has a bowl full of water and nothing seems to be draining out !!!??? Anyone have any ideas bout what going on???? HELP !!!!

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Are you sure the piece of hose is going into the tank and not bending in the pipe..I have had this same issue,it was a blockage at the pipe right at the top of the top the tank. Took awhile to get the hose to maneuver thru the pipe and into tank. Once done the water drained out of toilet. I then hooked up water to hose and completely flushed pipe and tank out .

Re: Help .. I'm Baffled !!

Maybe its time to call in a Professional RV Tank Cleaning service with the diagnostic/remedial equipment, and protective materials to handle a potential sewage spill. Do a websearch and see what you can find in your area, and/or ask the campground management for suggested vendors.
Maybe your tank could be pumped out from the top by a sewage pumping company with a suction hose going into the toilet and down as deep as possible into the tank.

Good luck!!!

Re: Help .. I'm Baffled !!

Make sure the roof vent isn’t blocked or dropped down. Air needs to enter as the water runs out. Attach a backflush fitting to the sewer connection and gently push some water back up the piping. It’s possible that a piece of cut-out from installing the plumbing for the tank has found its way to the valve opening. That or a large wad of TP/sewer trout is blocking it.


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Re: Help .. I'm Baffled !!

This is definitely an odd one. Every logical explanation seems exhausted by the OP's first post and followup posts.

I agree with wdk450....time to have a look into the tank. They can insert their high pressure jet/camera to see inside, then you will know what repairs, if any, may be necessary. Good luck!

Re: Help .. I'm Baffled !!

Have you tried backflushing (post #2)?

Re: Help .. I'm Baffled !!

With a clear back flush adapter on the sewer line with a shut off valve between it and the sewer hose, you could fill the piping with water (black tank valve open) being careful not to pressurize the tank with it. Then shut off the water and quickly open the valve on the back flush adapter. It might create enough suction to pull whatever is blocking the tank opening through.

Re: Help .. I'm Baffled !!

Maybe its time to call in a Professional RV Tank Cleaning service with the diagnostic/remedial equipment, and protective materials to handle a potential sewage spill. Do a web search and see what you can find in your area.

EXACTLY what I did !! Problem SOLVED !! Thank you for the suggestion !!

Turns out, over the past 3-1/2 yrs, we had developed the dreaded "poop pile" .. I just knew that I was doings the proper things to avoid just that issue. NOT !! .. The svc tech, here in Mesa, AZ was very knowledgeable, and shared tips to hopefully avoid the problem from reoccurring. Including treating the GREY tanks once a month with the same packets a lot of us use in the black tanks. The grey tanks are a petrie dish for black mold, and that's what some RV'rs sometimes smell inside their coaches. !! Who knew!!

Thank you to everyone that responded to my post. It was a nerve racking, lost a lot of sleep, last 24 hrs!!

Re: Help .. I'm Baffled !!

so what are these packets your talking about?

Re: Help .. I'm Baffled !!

Toy1Ton said:

so what are these packets your talking about?

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Was talking about any one of the toilet "drop-in" dissolvable packets, i.e., Camco, Thetford, etc. !!! Available at Walmart, Camping World, Amazon, etc!!

Although, I NEVER just "drop-in"!! I dissolve & stir-up in a large plastic cup, then pour into toilet!! Jus Sayin!!

Re: Help .. I'm Baffled !!

So what tips did the professional offer?
I am just curious to hear if there is anything extra I could be doing.

Re: Help .. I'm Baffled !!

Happy to hear you got this resolved Bill!

Do you think you have a leaky black tank valve where your liquid effluent is slowing leaking into the CG sewer, leading to the "pyramid"?