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Old 06-08-2014, 07:58 PM   #1
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Black tank won't dump!

On our last trip we were on a full hookup. I let the grey water run for the first 4 days, then shut it off the last 2 days to have slinky rinse water. When packing out on the last morning the black tank was full and I pulled the valve to let it empty. I got what seemed like about 5 gallons then it stopped. I went ahead and finished breaking down camp and hooking up followed by laps around the campground before attempting again at the dump station. No luck... Tried again after towing 200 miles home..... Nada. Read the internet for tips and settled on adding Rid-X (1,000 gallon tank dose) and waited it out for 2weeks..... Nothing. Tried filling the slinky with water and elevating it to back wash into the tank. Probed it with an old water hose and even getting over 8ft of it up the pipe and jogging it around and hearing it flopping around in the tank I barely got a trickle. I have now added another (Quart) of Robic and am back in wait mode. I'm kind of at my wits end on what to do besides calling out the pump truck. I don't know what the pumpers do on a case like this, but I'm kind of afraid of letting them touch it wondering if they might damage anything with the vacuum.

This is my second trailer, I've been RVing for about 5 years. We choose our paper carefully although not necessarily RV paper and always use a tank treatment each outing. We rarely are on a full hookup, but when we are we don't have the black tank open until it's full. I'm not sure what went wrong this time but it's sure a mess.

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Old 06-08-2014, 08:10 PM   #2
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You sure it's even full? The fact that the hose is in the tank and you hear it tells me it's empty.

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Old 06-08-2014, 08:20 PM   #3
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I agree that the tank is probably empty. Have you tried dumping a 5 gal. bucket of water in the toilet?
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Old 06-08-2014, 08:32 PM   #4
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Yep,,, could be the level indicators are lying to you... The tank may be empty.....
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Old 06-08-2014, 08:34 PM   #5
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I'd flush out the black tank by way of the toilet a couple of times, watching the water level with a flash light into the toilet to make sure you don't overflow. You can't really go by the tank sensors, showing the tank is or or even full, as toilet paper can stick to the sensors and give you false readings.

When you used a hose to clean things out, did any water/liquid come back out? Unless someone threw a large, solid object into the toilet, it seems unlikely to me that the black tank line is so packed that nothing comes out at all.

When I camp at a site with full hook-ups, I like to keep the black and grey tank valves closed, then add extra water before dumping the tanks. I do this every other day and when getting ready to depart, after dumping the tanks for the last time, will run water into both tanks one more time to help flush everything out.
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Old 06-08-2014, 08:59 PM   #6
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This happened to me a few weeks ago after 4 years of fulltiming. Usually dump once a week, sensors don't work, pulled the handle and there was no rush as normal. Thought I had a clog even though I normally flush twice. I'm not that adventurous to stick a hose up to try and clear a blockage. Jumped on line and ordered a flush king with 2 day shipping. It arrived as promised. Hooked it up, opened the valve and out it came without even turning on the water supply!
I assume the original problem was I had not closed the valve 100% or it was blocked from closing by a wad of something allowing the liquids to leak but opening and closing when trying to dump sealed it and our two days of use added enough liquid to allow a flow.
I did use the flush king till things cleaned out but now back to regular built in tank flush.
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Old 06-08-2014, 09:07 PM   #7
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If you can stick 8' of water hose up the tank and hear it flop around, the tank is empty. If there was a clog, it would be at the point where the drain pipe connects to the tank and your hose went waaaay past that point.

i agree with previous post that if the black tank valve was just a little bit opened, water could have leaked out and left solids.....but you said it flowed good for about 5 gals....so I doubt if that is the case either.

So I'll ask the same question as above....when you put the hose up into the tank, did you have the water flowing into the tank from the hose and was it coming out???

Everything points to an empty tank.

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Old 06-09-2014, 04:07 AM   #8
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I never rely on the gauge either.

Tank was used by 2 for 6 day outing and was full enough to gurgle when flushed. There had to be more in it than what it initially got out if it on first attempt.

I can see the water level in the tank is just below the toilet valve.

What little fluid I have gotten out has been added back trying to flush back the clog.

It's full.
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Old 06-09-2014, 05:47 AM   #9
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So then the hose wasn't in the tank flopping around. Best bet then is to get them to suck it out.
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Old 06-09-2014, 06:03 AM   #10
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Sounds to me like your blockage is between the toilet and the tank. Try running your hose in from the top thru the toilet. I have had to do this a couple times myself. I start without water running if I can see water in the down tube then when I get the clog clean use my toilet wand to flush it better.
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Old 06-09-2014, 07:41 PM   #11
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Well I listened to y'all, thought about it and put more of the pieces of the puzzle together and now know what I have is a teepee situation that is so severe it has blocked the inlet into the tank.

Yep, the tank didn't have much fluid in it, it's mostly solids. The standing water visible down the toilet was what was being held up by the stacked solids. The part that kept me thinking about it was being able to hear the hose banging around in there. It did sound empty, but what I was seeing was stronger evidence than what I was hearing.

I cleared the inlet, topped the tank off with water, dumped it and got minimal solids, but it did dump freely. I have it filled back with water and am going to let the Roebic and Rid-X work on it again. Before attempting the next dump, I'll probably hook it up to the truck and give it a good sloshin' to help break it up.

This is probably not something that happened just on the last trip, but something that has been accumulating for several trips. I'm gonna have to change something in my routine to make sure this doesn't happen again.
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Old 06-09-2014, 07:56 PM   #12
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Some have recommended dumping in a bunch of ice cubes and driving around allowing the ice to scrub and break up solids.
Jim & Sandy, Columbus, OH
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Old 06-09-2014, 08:15 PM   #13
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When I am finished dumping my tank at a campground, I always make sure the tank has a couple of inches of water and chemicals in it before I head down the road. This serves 2 purposes. 1. it sloshes all over and cleans the tank on the ride home. 2. your tank is ready the next time you head out. Just a little food for thought.
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Old 06-16-2014, 09:05 AM   #14
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one of our Grandkids flushed a HEAVE freezer bag, I wound up shoving the hose up drain line and back flushing, worked great.

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