Washing machine drain standpipe overflow

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by stephencc, Oct 3, 2021.

  1. stephencc

    stephencc New Member

    Joined:
    Oct 3, 2021
    Location:
    tn
    My clothes washing machine drain standpipe overflowed water when the machine was emptying, so I augered the pipe over 15 feet and I even had a plumber do the same while he was there for something else. But when I poured water into the standpipe to check it before using the machine again, the water came up to the top and stood there. So I augered it again and the same thing happened when I checked it again.

    Then I noticed that if I simply put the 'snake' straight down the pipe with my hand until I reached the P-trap, the water level went down, if not all the way to the P-trap then at least close. This was despite the fact that there was no resistance and nothing on the snake when I pulled it out. Yet when I poured water down the pipe again, it still rose back up and stood. So I was baffled by that.

    And then I noticed that the water level was stopping at the place in the standpipe where a pipe branches off at an upward angle towards the A/C unit. And so I poured more water down the pipe and somehow the water level didn't rise, it started going up the inclined pipe towards the A/C unit, which seemed to defy physics. I again pushed the snake down the pipe by hand with no resistance just to the P-trap and the water went down right away to at least close to the P-trap. So I am completely confused.

    I would really appreciate any thoughts on this. I am still afraid to use the washing machine until I can add water to the drain pipe without the water level coming up, which is how I had checked it before when I had problems in the past without this strange result.

    Thanks for any advice or information!
     
  2. breplum

    breplum Member

    Joined:
    Oct 2, 2004
    Occupation:
    Plumbing and heating contractor
    Location:
    San Francisco Bay Area
    Not knowing details of the drain system pieces, there is no way to know what is going on. Is this a standard two inch drain set up?
    Snaking from the roof vent, and fully snaking all the way to the main building trunk would normally attend to every possibility for a properly functioning laundry.
     
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  4. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    How about a line sketch that describes a side view of how you think the piping is?
     
  5. stephencc

    stephencc New Member

    Joined:
    Oct 3, 2021
    Location:
    tn
    thanks
    It is a 3 foot high pvc pipe that is about 1 inch in diameter, but it goes into the floor (ground floor) before the p-trap, and into cement foundation from what I understand, so it can't be seen or worked on. It was built in the 1960's, and uses copper pipes that may have rusted or corroded. I augered from the top of the standpipe, down through the p-trap and on for about 15 or 20 feet, and the plumber did the same. I may be that the pressure from the washing machine's drain tube would push on through, but I am nervous to try. What is so confusing is the way it fills right back up from simply pouring a little bit of water down it and stands at that level, like the clog is right there before the p-trap, and then it goes down easily by simply sticking the snake down to the p-trap with no resistance or spinning. But there is nothing down the standpipe to see and nothing on the snake when I pull it back out.
    I don't suppose the plumber could have installed a flap at the floor level of the standpipe, that only lets water through when there is pressure?
     
  6. John Gayewski

    John Gayewski In the Trades

    Joined:
    Aug 7, 2021
    Location:
    Iowa
    Your washing machine standpipe is 1" in diameter? It's pvc but copper underground?

    Something is off
     
  7. stephencc

    stephencc New Member

    Joined:
    Oct 3, 2021
    Location:
    tn
    Thanks, apparently it is '2-inch' pipe, according to the plumber, I had estimated from looking inside the pipe which looks smaller.
    The plumber came back out today and augered it three times and the water finally went down when poured into the standpipe, but he said the problems will continue because the p trap is copper and probably corroded, (it is underneath the floor in cement slab built in 1969). So it took about eight snake attempts overall despite being a new problem.
    He said maybe it is pieces of metal clogging the pipe. So I might have to have the p-trap replaced, which would mean drilling into the slab beneath my floor.
    I don't know if baking soda and vinegar would help with something like that, or some enzyme-based declogger? any suggestions?

    He was just as mystified as me when I told him how water traveled up the condensation pipe without coming up the stand pipe. It is like there is a sponge in the pipe that goes up to the a/c unit. But I guess that won't be a problem, go figure.
     
  8. stardust

    stardust DIY-er

    Joined:
    Oct 4, 2021
    Location:
    California
    I'm not sure I understand your description, but is it possible you have sand/rust/dirt in the P-trap that's stopping the water flow but can be pushed aside by the snake?

    It would be interesting to attach a 3/4" tube to a shop vac and see if you can suck something out of the trap.
     
  9. stephencc

    stephencc New Member

    Joined:
    Oct 3, 2021
    Location:
    tn
    Thanks,
    Yes perhaps there is a partial clog in the P-trap and a flap at the start of the trap, such that they combine to stop poured water (with no pressure) but when I insert the snake by hand until I hit something at floor level (perhaps a flap) the water can flow through the partial clog in the trap. At least that’s my newest guess.

    the plumber only went a little ways with his snake. I don’t think he even passed the second turn. Yet, after three tries, it was clear to pass the poured water. So that, along with only needing a few cups to fill up the standpipe, makes feel that the problem must be in the trap,
    Someone suggested a drain camera , to try to look at the trap. I might try that before I try to vacuum something out, but that’s an interesting idea though.
    Thanks
     
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