My problem is related to this question, but I'm not sure which of the proposed solutions I should consider.

We have a front-loading washer (LG WM3400CW).

The drain system that came with this old house starts with the main drain pipe about 4' above the basement floor. The stand pipe ties into this using 2" PVC pipe. It has a trap just above the main pipe and used to have about a 1' stand pipe above that. We periodically had overflows but did not want to seal the washer drain hose to the stand pipe, so I added about 1.5' of 2" PVC vertically, and now the drain hose enters the stand pipe about 6.5' above the floor.

According to the washer's manual, we are well within specs. It says the drain hose can extend up to 8' from the floor. The original drain hose easily reaches the new stand pipe opening.

Our overflow problem seems to have gone away, and I don't think it's siphoning back in.

But our new problem is that after each cycle, there is a small amount of standing water in the back of the drum. This makes the spin less effective because some of the clothes come out wet rather than damp.

Is this a washer repair issue? For instance, does it have its own check valve that's defective? Is an external check valve at the base of the drain hose the answer? Is there something else we can do to reduce the water left in the washer?


  • 2
    Is the water there immediately after draining, or does it accumulate in the time before the next use?
    – isherwood
    Commented May 12, 2023 at 20:03
  • Did you install the check valve that some answers recommended? If not, you're getting 6 feet of backflow. Run a small cycle with no clothes. After the spin, look in the tub and see if water rushes back in. If it does, it's backflow.
    – MTA
    Commented May 12, 2023 at 20:59
  • It sounds like you are siphoning water back from the drain. Switch to a 2" stand pipe as the washer instructions suggest.
    – Gil
    Commented May 13, 2023 at 0:09
  • I will check again about the timing. It seems to be pretty soon after the cycle ends. @MTA, I have not tried anything yet, hoping for advice as to why the washer itself is not handling the backflow, when it says it can handle 8 feet.
    – vknowles
    Commented May 15, 2023 at 13:35
  • 1
    Does this answer your question? What happens if the washing machine discharge hose is too far down the stand pipe?
    – Armand
    Commented May 15, 2023 at 15:06

1 Answer 1


It appears you have it connected properly and that the hose goes well above the washer. With the 2" PVC air will flow around the hose so it cannot suck water out of the pipe when it is below the hose outlet. When draining the water will pump out of the washer but it does not flush the hose so water remains in the hose when the pump stops. This will flow back to seek equilibrium which in your case is above the washer tub bottom so water will appear there. There are two solutions lower the drain pipe which appears to be out of the question or add a check valve in the drain line as suggested by another user. Good Luck!

  • Just to be sure, isn't the washer supposed to have its own check valve to handle back flow from its own hose? The question is whether I need to repair the washer or just add a check valve. Thanks!
    – vknowles
    Commented May 17, 2023 at 21:40
  • To the best of my knowledge no. Your problem is not the same as a typical install.
    – Gil
    Commented May 19, 2023 at 18:48

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.