Unclogging a Backed Up Toilet Holding Tank

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My toilet holding tank is backed up. I turned the water off. I put chemicals in it, it’s still stopped up. Is there another lever beyond the valve?

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I would suggest purchasing a small plumbers “snake” and see if you can go down the toilet and possibly find the drain tube? It’s a long shot but much cleaner than the other option which is to go from the outside valve and up. If you get a long enough snake, you can leave the hose connected and go up through the hose, past the valve and to the clogged area.

Typically there is not another valve other than what is at the bayonet. Another issue might be the valve is not opening, just the handle moving, especially if it’s a cable handle/valve.

Hope this helps,
David Solberg

Proper RV Toilet Maintenance
Troubleshooting An RV Toilet
Quick Tips For Better RV Toilet Operation

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73 Responses to “Unclogging a Backed Up Toilet Holding Tank”

  1. Lisa Hadley

    Soooooo we have a Monaco Windsor and we thought we were supposed to leave valve open when connected to sewage. Newbies (can you tell) Now our tank is showing full but we don't see where it's draining into sewage system. Any recommendations on what to do?

  2. Terry Brandon

    I recently had this same issue and tried every suggestion out there, snaking it, spraying from the toilet side and many others that ended up costing me hundreds of dollars in devices and chemicals. My tank was full and unusable. I was desperate for a solution, and I purchased a small electric pump ($100.00) from Harbor Freight and pumped the tank out from the top side, not a pleasant job. At this point I went to Campers World and purchased a devise ($ 60.00) that connected to my wastewater pipe. This devise allowed me to connect to both the RV wastewater drainpipe, my city water via a hose connection and attach my waste pipe going septic tank to the device on the low side. The devise came with a built-in valve that allowed me to stop the flow of wastewater to the sewer line and create a seal to allow the city water pressure to build against the clog at the black water tank. At that point I closed both of my gray water tanks and opened the black water tank. Turned the water on and cleared the clog back away from the drainpipe at the black tank. My wife watched the toilet to make sure I did not overfill the holding tank. After filling the black water holding tank to near overflow, I turned the water supply off, opened the valve and let the tank empty. I did this several times a day over the next several days to ensure all waste that had attached itself to the holding tank was loosened and expelled. My efforts prior to this point were many and all were very unpleasant and unsuccessful. I am very pleased to say that this method was the least unpleasant and most effective. But, in my opinion your best bet is to clean regularly, use RV tissue, a good chemical to help dissolve the paper and matter and make sure you keep several gallons of clean water in your black tank after each time you empty it. I learned the hard way, but I am a newbie to RVing. Hope this helps.

  3. Douglas Fletcher

    Where can I get parts for my RV

  4. Andrew Hansborough

    Is there a way to manually close the slides if the system failed to close them?

  5. Dave Johnson

    Hot water heats with electric only. Lights off with gas but shuts off when timed out. I changed the thermo device but that did not solve the problem.

  6. Scott Gilley

    My motorhome does have two valves. I didn't know this the first time I had to dump and just couldn't get it to dump. The second valve was located to the back of the compartment behind the other valve. It was kind of hidden behind the other valve.

  7. Stephen Smith

    There is a snake that is actually a hose with a twirling valve at the end. This broke up the pyramid in my black tank. I use the chemicals everyone suggests plus Dawn and vinegar. What solves this problem is to always leave black tank with ¼ full with water, even when you are using full hookups. Poop when it hits a dry tank makes a pyramid. Poop is lighter than water so it floats or disperses throughout the black tank! Always leave some water in the black tank!

  8. Ladislao Pavia

    back bottom corner slide out dont shut all the way on my dining table side.

  9. Meegan Fringer

    We have a toilet not properly draining. This model (which is unusual) has two bathrooms, one in the main bedroom and one in the other end next to the bunk beds. The user guide that I found for our 5th Wheel does not show this layout, it shows a one toilet version so I have no help there. The problem toilet is in the main bedroom. We have tried boiling water, toilet chemicals, snake, etc. When we flush the water level is just below the opening and smells of course. The water level never gets low enough for us to make a close inspection and we are unsure of what the 3 valves pertain to under the front near this toilet because we do not have the schematics for it. Ugh. How do we tell if a valve is not opening even though handle moves in and out? Anyone have a video on this situation that we can watch?

  10. Chris Barbot

    Black holding tank burst in cleaning it. Was the first time we filled it to the top as our gauges weren't working. We weren't even full when the thing started making noises and broke through the enclosed underbelly. How hard are these to replace or repair? We're hoping to make a positive out of this and install tank heaters. Are these very hard to do? Upgrade of inverter necessary? Sure glad we had cleaned it! Oh ... where would we get more underbelly if necessary? Thanks so much for any help / sources you can provide! Chris