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Old 07-26-2016, 06:39 AM   #1
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Black Tank

Anyone had black tank not draining. Gauge says 2/3 full but not emptying. Any help is much appreciated.
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Old 07-26-2016, 01:42 PM   #2
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Are you sure it's not draining? You cannot rely on the tank level gauges. Debris sometimes gets on the sensors, and will cause inaccurate readings. Try flushing your tank well. That might help. We full-time, and never use the gauges. Debbie and I can't go 7-10 days without emptying the black tank. When it's starts getting full, we can hear a difference in the flushing... sounds like the toilet is "burping".

Bob and Debbie (both retired) with Senior FurBabies Grizz (a German Shepherd mix) and Bailey (a Lab mix)...and sometimes a Grandkiddo or 2! Full Time RVers since July 2013 Redwood: 2012 36FL with sliding patio doors
Tow Vehicle: 2011 Chevy Silverado 3500 HD with 6.6 DuraMax Dually
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Old 07-26-2016, 02:25 PM   #3
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As Grizzby suggested, flush the black tank and see if it is draining. I suggest you get a clear 45 deg. fitting to put on your hose where you hook it up to your trailer. Then you can see if it is draining and when it is cleaned out.
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Old 07-26-2016, 02:25 PM   #4
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Originally Posted by ccmack View Post
Anyone had black tank not draining. Gauge says 2/3 full but not emptying. Any help is much appreciated.
Don't go by the gauge. I never even bother to look at our gauge anymore as it always reads "2/3."

How do you know it's not draining? Vaughan recently installed one of the clear connectors on ours which helps letting us assess whether the black tank has been adequately flushed, but even before that, we could hear it flushing.
"Life is too short to take the same road twice"
Vaughan and Tracy, and our 4-legged fur babies: Zeus, Millie, Murphy and Miles, traveling happily in Tilda, our 2013 RW 36RL.
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Old 07-26-2016, 04:16 PM   #5
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Guess we were relying on gauges. will have to pay more attention to sounds. Thank you for your response.
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Old 07-26-2016, 04:17 PM   #6
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Great idea! Thank you.
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Old 07-26-2016, 05:45 PM   #7
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I am going to add my two cents worth so maybe my experiences can help someone. I too had problems with the black tank not wanting to dump when I knew it was full. This started about two months ago. Please note that I am full-time and have lived in the RW for about one and one-half years. I typically use the black tank flush after each dump to clean the tank out. I assumed it was a broken or inoperable cable on the dump valve so I went and purchased another one. I waited a few days as I was not looking forward to doing this job. Before I pulled the underbelly down I tried dumping one more time and it appeared to dump OK (I have a clear elbow going into the septic tank inlet).

Fast forward two months and the same problem occurred. I partially pulled the belly pan down and confirmed that nothing was wrong with the tank valve. This led me to believe it was a plugged valve or tank opening. I purchased one of those back flush devices with the clear elbow, water hose connection, and gate valve. Well I closed the black flush valve, opened the black tank valve, and then turned on the water. I did not run it long as I knew the black tank was almost full. I turned the water off and opened the back flush valve and started to get waste passing through. I did this several times and appeared to keep getting waste passing. After completely draining (at least I thought so) the black tank I went in and poured several cups of laundry detergent down the toilet and went back and started back flushing more. I figured I would sit down a minute and enjoy a cold one for my victory (water only for this boy). I know only 3 to 4 minutes transpired when I heard a loud noise and water was dumping from the underbelly. And it was not totally clean water either! It appears there was still waste in the tank and it did not take as long as I thought to completely fill the tank up.

I lowered the rest of the belly pan as I had a literal mess on my hands now. On my RW the black water drain pipe was only inserted into the black tank with no adhesive. There was a pipe clamp over the conduit but for what reason is beyond me. Looking back I am glad it was not glued as it allowed the pipe to partially move back from the tank when I over pressured the tank. I took a long break and let what water was in there to drain out ( the pipe did not complexly come out). I then reached underneath the drain pipe and pushed it up and it popped back into the black tank opening.

I must mention that I would occasionally get a sewer smell underneath the RW. I did not know if it was from the coach or my septic tank opening (I keep it capped when not dumping). I now think that I may have been getting some smell from the pipe tank connection since it was not glued. The foil barrier showed some evidence of intermittent moisture from somewhere. I am going to add a mastic material we using on medium voltage electrical connections to prevent moisture ingress. I am going to place it around this connection. In addition, I am going to place a 3 inch plumbing repair doodad made out of rubber with two hose clamps. I am going to have to shorten it and also cut a slit in it to place it around the pipe. I really think the mastic alone is sufficient to stop possible water seepage as it should not occur if I do not add excessive pressure to the system.

Lessons learned:

Make sure you do not go skimpy on the water usage using the black tank as a full timer. It can cause the waste to solidify, partially or fully blocking the valve and/or tank opening.

If using one of the clear black flush elbow valves be very cautious and never walk away from it. Run it awhile and then dump until clear.

In between using the back flush elbow also use the RW back flush as it seems to spray the upper walls in the tank and assists in the cleaning process.

I have been flushing every once in a while for several days now and almost got the tank perfectly clear now.

Dean & Cindy (Go DAWGS)
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Old 07-26-2016, 07:39 PM   #8
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Where else in our social circles do we have an opportunity to talk about poop so openly, and with such enthusiasm!
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Old 07-26-2016, 07:51 PM   #9
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Thank you for sharing your experience and the pictures!
Looks like Scott has a new project this weekend. ��
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Old 07-27-2016, 12:22 AM   #10
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Mine came apart at the same spot. What happened with mine was the valve side of the tank fell out of the supports causing that connection to alow the tank to be lower than the plumbing so the waste would not flow. I had to jack the tank back up and it started flowing
2015 36RL pushing a 2015 Denali
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