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N-Trouble's avatar
N-Trouble
Explorer
Dec 02, 2014

Toilet plumbing?

Several days ago I had posted about large air bubbles burping back up through my toilet when flushing. Come to find out its not a venting issue rather looks to be an issue with how the downpipe from the toilet to the black tank was installed. Waste and TP had collected at the bottom of the downpipe not allowing air to pass.

With the tank cleared out I ran a tape measure down to the bottom of the tank and measured the distance to the toilet seal. I then raised the tape measure to the bottom of the downpipe and again measured to the toilet seal. The difference in height is only 3.75". If I crawl up under the trailer and measure the height of the black tank directly under where the toilet is located it is a good 6-7" deep. Why would they route the downpipe so that it sits 2-3" down inside the black tank? Is this common, or any reason to do this? All I can see this doing is significantly reducing my black tank capacity. Once the water level in the tank reaches close to the 3.75" level nothing is going to clear from the downpipe and will continue to backup. Did the manufacturer screw this one up?

7 Replies

  • Some lines to waste tanks (vent/drain/dump) use a grommet/gasket and some are glued to fittings.

    Also some black waste tanks have a 'sloped shelf' when 'stuff' drops....idea was to have an area where stuff would slide off vs flat plop area.

    When going #2 is everybody using plenty of water to flush???
    Filling bowl just prior to flushing?

    Call mfg. Talk with production line supervisor/manager and get information on install and suggested ways to fix.

    Production line folks have been very helpful to me in past vs 'customer service'
  • N-Trouble wrote:
    CloudDriver wrote:
    N-Trouble wrote:
    Did the manufacturer screw this one up?

    Sure sounds like it from your description. If it's still under warranty, take it back and get it fixed. If out of warranty you could do it yourself by removing the toilet, unscrew the floor flange and pull up the flange and drop pipe, cut the drop pipe shorter and re-install.


    Yes still under warranty but if its this easy I may just do it myself as pulling the trailer out of storage may be more work. I would also know its done correctly by doing it myself. I wasn't sure if the black tank had to be dropped, but it doesn't sound like it based on your description.

    One thing that's not clear to me is what seals the drop pipe to the top of the black tank?


    Our Minnie has a rubber "grommet" in the hole where the drop pipe and vent stack enters the tank. The grommet is the seal. Probably something similar in your RV, but the best bet is to call the manufacturer and ask.
  • DutchmenSport wrote:
    If under warranty take in back. But ... you have an alternative when dumping; just hold the foot pedal of the toilet open when dumping your black tank. This will break the seal if the waste water is higher than the end of the pipe, and will allow it to flush out. Flushing your toilet? Every time you push the toilet peddle, you've broken the seal, so everything should go down, no problem.

    It's not a fix ... it's a work around until you can get it fixed.


    Thanks but my concern isn't with dumping the tank as it has a built in hose fitting for a black tank flush that will push everything out. I'm more concerned with the tank prematurely backing up while camped as happened to us last time.
  • If under warranty take in back. But ... you have an alternative when dumping; just hold the foot pedal of the toilet open when dumping your black tank. This will break the seal if the waste water is higher than the end of the pipe, and will allow it to flush out. Flushing your toilet? Every time you push the toilet peddle, you've broken the seal, so everything should go down, no problem.

    It's not a fix ... it's a work around until you can get it fixed.
  • CloudDriver wrote:
    N-Trouble wrote:
    Did the manufacturer screw this one up?

    Sure sounds like it from your description. If it's still under warranty, take it back and get it fixed. If out of warranty you could do it yourself by removing the toilet, unscrew the floor flange and pull up the flange and drop pipe, cut the drop pipe shorter and re-install.


    Yes still under warranty but if its this easy I may just do it myself as pulling the trailer out of storage may be more work. I would also know its done correctly by doing it myself. I wasn't sure if the black tank had to be dropped, but it doesn't sound like it based on your description.

    One thing that's not clear to me is what seals the drop pipe to the top of the black tank?
  • N-Trouble wrote:
    Did the manufacturer screw this one up?

    Sure sounds like it from your description. If it's still under warranty, take it back and get it fixed. If out of warranty you could do it yourself by removing the toilet, unscrew the floor flange and pull up the flange and drop pipe, cut the drop pipe shorter and re-install.
  • They did it that way because they were in a hurry and just didn't care.
    Mine is very similar and I suspect the vent is about 2.5" down into the black tank. This means I too get the dreaded burp when it's near 7/8's full.

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