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drillagent's avatar
drillagent
Explorer
Sep 05, 2014

Black Tank Won't Empty

Ok, so a couple of weeks ago, we take our new to us 5er out for it's maiden voyage to test everything out. Along with a couple of other issues, I found that the black tank sensors were saying the tank was 2/3 full. Can't be, so I flush the tank several times. Each time I notice there's still fluid in the tank even though there's nothing coming out. Can't seem to get it all out and the flush is running clear and we have to go home.

This week I park it at the Auto Craft Shop so I can work on it and get it ready to go back out this weekend. I bought some sensor cleaner at Camping World which said to fill the tank and let it slosh around while I'm driving. When I go to pour water in the toilet, I notice a bunch of tiny maggot looking worms attached to the underside of the flush ball thing. Gross. Then while I'm using a five gallon bucket to fill my 50 gallon tank, I can only get eight buckets into the tank before it's already coming up through the toilet. Which tells me there was still 10 gallons in the tank.

So yesterday, we pull in and get set up and I empty the tank, and again, after the flow stops, there's still fluid in the tank.

What gives? Why won't the tank completely empty? Is it supposed to maintain nasty water all the time?

40 Replies

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  • Nutinelse2do's avatar
    Nutinelse2do
    Explorer
    Sep 05, 2014
    Sounds like the dreaded brown mound. Instead of worrying about it and spending time trying to fix it yourself, which may, or may not work, take it to your local rv supply/ repair place and spend the $100 to have all the tanks professionally cleaned. Then you know you will not have any future issues.
    JMO

    Cheryl
  • Big_Katuna's avatar
    Big_Katuna
    Explorer II
    Sep 05, 2014
    First thing is the gauges are useless. And you can buy a USB camera for your laptop for like $30 on Amazon or EBay. If you open the valve and 40 gallons comes out it's probably empty and you have a 40 gallon tank. Wouldn't be the first time a maker made that mistake. Also, you can have an RV shop power wash your tank for $100 or so.
  • fj12ryder's avatar
    fj12ryder
    Explorer III
    Sep 05, 2014
    When we flushed out our used 5th wheel for the first time I noticed that there were solids coming out when we dumped. Since we never use the toilet for solid waste I was cleaning out the old "stuff". That went on for many tank emptyings before we no longer got solid waste out.

    It sounds like the person/s that owned the trailer before you didn't take enough care when cleaning things out. You may need to run a hose into the trailer, open the toilet, and use the hose to do some serious washing directly under the opening of the toilet. The whole thing is gross. Which is why we don't use the toilet for solid waste. :)
  • bukzin's avatar
    bukzin
    Explorer
    Sep 05, 2014
    I would avoid harsh chemicals if possible.


    I believe Harbor Freight sells a small camera system on a gooseneck you you could
    use down the toilet.
    I got one at Costco. $125 I think.


    On my DP the cheap gauges always says there is more in the tank
    then what its really holding, by double.
  • drillagent's avatar
    drillagent
    Explorer
    Sep 05, 2014
    Is it safe to put an industrial strength drain cleaner, like liquid plummer or something into the tank? That should dissolve any solids stuck in there, right?
  • darsben's avatar
    darsben
    Explorer II
    Sep 05, 2014
    Could be the tank is tilted away from the drain. Jack up opposite side of trailer so that the drain is for sure the lowest point and see if more drains out
  • BTPO1's avatar
    BTPO1
    Explorer
    Sep 05, 2014
    the bear II wrote:
    It should empty completely....every tank I've ever seen the bottom slopes towards the dump valve opening. There may be some residual liquid like a cup or so but nothing like you are describing.

    Sounds like you might have the "Pyramid of Death". A pile of solids at the bottom.

    You can try dumping a couple of bags of ice in the tank and then drive around to see if it will break up any solids.

    If that doesn't work then it's time for a camera to see what might be stopping it up.


    X2, then maybe a good power flush through the toilet to flush the solids that have been left from the previous owner not dumping properly. JMO
  • the_bear_II's avatar
    the_bear_II
    Explorer
    Sep 05, 2014
    It should empty completely....every tank I've ever seen the bottom slopes towards the dump valve opening. There may be some residual liquid like a cup or so but nothing like you are describing.

    Sounds like you might have the "Pyramid of Death". A pile of solids at the bottom.

    You can try dumping a couple of bags of ice in the tank and then drive around to see if it will break up any solids.

    If that doesn't work then it's time for a camera to see what might be stopping it up.

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