Forum Discussion

krazymatt's avatar
krazymatt
Explorer
Jul 06, 2015

Black Tank Backing Up-Please help!

So we've gone dry camping twice in a new to me 2002 Cougar Fifth wheel. Both times we've had a blacktank/toilet backup issue. Emptying the black tank does not help. Yes I know about putting enough water in there and all that. It appears the solids/paper are just not making it into the tank and they back up by the second day to the toilet. The first time I poked it from the top with a rotorooter type snake while my buddy banged on the tank from the bottom in the area where the pipe goes in and it finally went. This last time I just poked it and it seemed to go easier this time but I'm not sure if it's a bad design or what. There are two 45 degree elbows on the way down because the tank is not directly under the toilet. I used to have a TT which never had this issue. How hard is it to remove the black tank? Any ideas? Thanks....

30 Replies

Show More
  • bamcote's avatar
    bamcote
    Explorer
    Jul 06, 2015
    My brother-in-law had an older Mako fifth wheel and had the same problems as you, even with using plenty of water to flush. Got to the point he would run a garden hose from the toilet side of the clog to try to break it up as well as the roto router. Etc. last clog was so bad he had to cut the pipes from below and fix it. Very shortly after that he traded it in. His new fifth wheel-the first thing he did when checking to purchase it was to see how the toilet dumped into the tank.
  • Dakota98's avatar
    Dakota98
    Explorer
    Jul 06, 2015
    Quote:
    The first time I poked it from the top with a rotorooter type snake while my buddy banged on the tank from the bottom in the area where the pipe goes in and it finally went

    Seems to me that may answer to the problem.

    Something is clogging that area. Try to find the largest round wire power tube brush close to the drain pipe diameter you can & using a flexible drill extension, ream it out. There may be burs from when the pipe was connected to the elbow & toilet paper is hanging up on that.
  • krazymatt's avatar
    krazymatt
    Explorer
    Jul 06, 2015
    the bear II wrote:
    My 5th wheel has two 45 degree elbows, one at the toilet flange and one where it dumps into the black tank. Never have clogs.

    Three common causes:
    1. The vent pipe for the black tank is clogged. Take the cap off at the roof and run a snake down the pipe or use a hose to run water down the pipe.

    2. Something is caught in the sewer pipe leading to the black tank. The toilet paper builds up and clogs the pipe. I've read where in the manufacturing process once in awhile stuff gets dropped down before the toilet is installed or kids drop things in toilets.

    3. Dried up gunk has created a pyramid and it's partially blocking the entrance into the black tank.

    Number one cause is the vent clog so I would check it first.


    Thanks for the info! So excuse my ignorance but; Does the vent go all the way into the tank as well??

    If there is a "pyramid" at the bottom; how would I help that disappear?
  • krazymatt's avatar
    krazymatt
    Explorer
    Jul 06, 2015
    Harvard wrote:
    Add water and dish detergent then take it for a drive over a bumpy road followed by a dump.


    Done that twice actually. Dawn and Borax. Very bumpy road; and very curvy hilly highway on the way home.
  • korbe's avatar
    korbe
    Explorer
    Jul 06, 2015
    My black tank has 2 45's also and we have never had that problem. If the clog happens on the way to the tank then it would seem to me that something is catching the flush contents and is not a smoothed wall run.
  • WyoTraveler's avatar
    WyoTraveler
    Explorer
    Jul 06, 2015
    krazymatt wrote:
    WyoTraveler wrote:
    As a starter I would check the vent to make sure it is open. Probably 2 elows before the tank may not be the best design. You may want to check to see if there is some restriction in the elbows that is not getting completely cleared out.


    Well the double 45 degree elbows I really don't care for at all. As far as restriction at those elbows I highly doubt as I pretty much have visual access to the first 45deg and it looks pretty clear when it's not backed up. My hunch is that the issue is where the pipe dumps into the tank as it takes a couple days for the stuff to reach the toilet. If it is indeed a bad design I could easily sell it and find something else as I don't have a lot of money into it. I really do LOVE the floorplan and everything else about it for my use of occasional dry camping but dealing with this is NOT what I signed up for lol.


    My previous TT was a great black tank design. Deep tank and no problems. My MH has a very shallow wide tank and I have to really pour in the water when I flush. In fact it is so shallow a couple of uses without a lot of water will start backing up right below where it empties into the tank. I try to make the bowl pretty full before I push the lever all the way down so lots of water goes in.
  • the_bear_II's avatar
    the_bear_II
    Explorer
    Jul 06, 2015
    My 5th wheel has two 45 degree elbows, one at the toilet flange and one where it dumps into the black tank. Never have clogs.

    Three common causes:
    1. The vent pipe for the black tank is clogged. Take the cap off at the roof and run a snake down the pipe or use a hose to run water down the pipe.

    2. Something is caught in the sewer pipe leading to the black tank. The toilet paper builds up and clogs the pipe. I've read where in the manufacturing process once in awhile stuff gets dropped down before the toilet is installed or kids drop things in toilets.

    3. Dried up gunk has created a pyramid and it's partially blocking the entrance into the black tank.

    Number one cause is the vent clog so I would check it first.
  • Harvard's avatar
    Harvard
    Explorer
    Jul 06, 2015
    Add water and dish detergent then take it for a drive over a bumpy road followed by a dump.
  • krazymatt's avatar
    krazymatt
    Explorer
    Jul 06, 2015
    WyoTraveler wrote:
    As a starter I would check the vent to make sure it is open. Probably 2 elows before the tank may not be the best design. You may want to check to see if there is some restriction in the elbows that is not getting completely cleared out.


    Well the double 45 degree elbows I really don't care for at all. As far as restriction at those elbows I highly doubt as I pretty much have visual access to the first 45deg and it looks pretty clear when it's not backed up. My hunch is that the issue is where the pipe dumps into the tank as it takes a couple days for the stuff to reach the toilet. If it is indeed a bad design I could easily sell it and find something else as I don't have a lot of money into it. I really do LOVE the floorplan and everything else about it for my use of occasional dry camping but dealing with this is NOT what I signed up for lol.
  • WyoTraveler's avatar
    WyoTraveler
    Explorer
    Jul 06, 2015
    As a starter I would check the vent to make sure it is open. Probably 2 elows before the tank may not be the best design. You may want to check to see if there is some restriction in the elbows that is not getting completely cleared out.

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,283 PostsLatest Activity: Jul 17, 2025