I currently live in a top and bottom condo and had a washing machine installed (with the piping) last November. My downstairs neighbor has recently notified me that she has been getting almost all water backfill into her tub when I run machine, even with the smallest load size.

I have tried on my end to understand why this might be and I feel bad that it is an issue she has to deal with. I contacted the plumber who did the work and he assured me that the piping that was installed is correct and up to code. For reference, he installed a 2in thick pipe that transfers water to a 1.5in pipe.

I am unsure of what the true reason would be as to why the water will not drain through our units properly. I know of other units that have a washer installed.

I am unsure of what else I can do to help mitigate the issue. I am unsure if she has a clog, but it is an issue that has been progressively getting worse. I tried contacting her landlord but he seems to not really care about the issue.

Should I try to install a flow restrictor that will slow the amount of water that is pushed through the pipe?

Should I get a new washing machine that does not use as much water (currently have a commercial grade GE washer)

Any comments or perspective would be greatly appreciated.

Thank you!

  • 3
    There is a clog pass the neighbours tub. Her tub might be draining slow also.
    – crip659
    Commented Jul 5, 2023 at 23:44
  • That's what I have been thinking and trying to tell her. Everytime it backs up she sends me a picture of her tub.I tried contacting the landlord but he does not care about the unit and the HOA is very hands off. She also can't get a plumber out since she does not own the unit.
    – user158841
    Commented Jul 5, 2023 at 23:53
  • If you are lucky, your city/town/county might have something in their landlord regulations to deal with this.
    – crip659
    Commented Jul 6, 2023 at 0:00
  • 4
    "installed a 2in thick pipe that transfers water to a 1.5in pipe." That's a violation under every plumbing code I know or have even a passing familiarity with. Drain pipe sizes always only ever increase as flow goes, per code. Draining a larger pipe into a smaller pipe is a violation.
    – Ecnerwal
    Commented Jul 6, 2023 at 1:10
  • Yeah I was unaware of the plumbing code and was not something I thought about when I had it installed. Either way, the plumber should have told me about that.
    – user158841
    Commented Jul 6, 2023 at 15:18

1 Answer 1


I would hire a plumber unconnected with the washing machine install to check the drain system and have them run a scope down that drain to determine what the drain pipe diameter is at various distances, and likely also identify the location and nature of the partial clog downstream of your neighbor's tub.

I found this 10-year old clarification on the NC state plumbing code (you didn't indicate where you are located, but this one sounds reasonable):

Clothes Washer Drain Size

Code: 2012 NC Plumbing Code Date: November 14, 2013 Section: 406.3

Question: At what point does the waste connection from an automatic clothes washer have to be a minimum of three (3) inches in diameter?

Answer: The minimum 2-inch drainage pipe is used for the standpipe, trap, trap arm to the vertical vent or waste stack and also for the vertical vent. As soon as the drainage pipe turns horizontal from the vertical vent or waste stack, the minimum drain pipe size for the horizontal drain is to be 3 inches. This minimum horizontal drain size is applied in all cases, regardless of whether it is a fixture drain or a branch drain

  • Hiring a second plumber is a good idea. I live in NJ. I am seeing standard drain pipes need to be at least 2", which is a problem because the pipes behind my walls are 1.5" so I wouldn't be able to replace those without ripping out other stuff. Plus I cannot do work to my neighbors unit. My current drainage is right next to my kitchen sink, which never gets any backfill..
    – user158841
    Commented Jul 6, 2023 at 15:22
  • Even though you can't do work to your neighbor's unit, if you run a scope down the inside of the pipe you might be able to identify what the constriction/blockage is past the neighbor's tub. Maybe it's something easy to clear from inside the pipe. Otherwise, it sounds like your issue is more peak short-term flow rate related rather than total volume. Maybe GE/other manufacturer has models that pump out water more slowly rather than the probably super fast pump of your machine.
    – Armand
    Commented Jul 6, 2023 at 20:44

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