Improper Venting of Laundry Tray/Sump Pump System & Misc

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Seneca Lake Monster, Mar 13, 2021.

  1. Seneca Lake Monster

    Seneca Lake Monster New Member

    Mar 13, 2021
    New York State
    Firstly I appreciate any and all professional advice that anyone here can provide. I read another thread on a similar topic a few weeks ago, and the original poster seemed to sustain an adversarial posture despite (and in spite of) the sound recommendations of the professionals on this forum.

    When I purchased my home it had a preexisting Flotec laundry tray system into which the basement utility sink drained (into which the previous owner's washing machine in turn, drained). The Flotec drain rises about seven feet until it becomes horizontal and joins the house wastewater line.

    My wife and I opted to place our washing machine next to the dryer (farther across the basement) rather than next to the utility sink. This necessitated a new approach to draining the washing machine. A local plumbing company installed a standpipe and drain line that now also drains into the Flotec--except when it doesn't.

    Almost always when the washing machine drains the drain water backs up into the utility sink before it eventually drains into the Flotec and/or is pumped away by the Flotec once the float reaches the trigger height for the sump pump. This seems wrong, as I would expect the Flotec, which is at a lower height than the sink basin, simply to fill until the pump runs without backing up into the sink.

    I think the cause of this behavior is that the vent pipe for the Flotec has an AAV at the top rather than tying into the house vent stack. The Flotec vent pipe was open to the basement when we purchased the house. The home inspector had noted that it violated code, so the same plumber that put in the washer standpipe added the AAV (rather than tying into the vent stack as one of his colleagues had originally recommended). I suspect that the AAV doesn't allow proper venting (out) of the Flotec when water rushes into the Flotec (where can the air go?). This causes air to try to escape where the power cords enter the top of the basin (hissing sound) and causes the washer drain water to back up into the sink until it can drain/be drained.

    I've attached photographs of my washing machine and drain system. Aside from this I've shared videos from my Google Drive that walk through all of what I've said here in more detail including a demonstration of the apparent problem behavior. The videos can be accessed here: Video Mar 13, 22 22 38-1.mp4 is a walkthrough of the plumbing an apparent problem. Video Mar 13, 22 40 02-1.mp4 is a little more info with another question. Video Mar 13, 22 50 38-1.mp4 is the problem in action. (Photos are here, too.)

    My assumption is that proper resolution would be to tie the Flotec vent pipe into the house vent stack. Also, as I noted in the second video, should the small drain hose from the water conditioning system drain into the Flotec drain pipe? It seems to cause Flotec to run even when there is no apparent water flowing in. Could this indicate that the check valve on the Flotec is bad?

    Thank you.

    Attached Files:

  2. wwhitney

    wwhitney Well-Known Member

    Mar 17, 2019
    Berkeley, CA
    Your diagnosis sounds correct to me. I would suggest confirming it by locating the manual for the pump; it should clearly state that the vent needs to be open to atmosphere.

    Is that an enormous lint filter just above the standpipe?

    The narrow black pipe (from the water conditioning system?) definitely seems like it shouldn't be connected that way. I would think it should go through an air gap and a trap. I assume it could just dump into the laundry tray. But I'm not so familiar with water conditioning systems.

    Cheers, Wayne
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  4. Seneca Lake Monster

    Seneca Lake Monster New Member

    Mar 13, 2021
    New York State
    Greetings, Wayne,

    Thanks for the sanity check on the Flotec. I was able to track down a manual via Home Depot for what appears to be the same base part number (FP0S1800LTS) ( It states

    Thread a 1-1/2" NPT exterior vent pipe into the second hole in the water box cover. Connect the vent pipe to the sewer vent system. You should install a union to allow easy removal for service.

    I think we can agree that an AAV does not qualify as "the sewer vent system". The vent stack allows the drain system to "breathe". The current configuration with the AAV only allows this part of the system to inhale (when discharging water) but not exhale (when filling).

    How is it possible that an experienced plumber would make this kind of mistake? It's also odd that my town's code enforcement officer affirmed the use of an AAV in this situation, but maybe his only concern was that with a properly-functioning AAV sewer gas should not be able to enter the basement (even though the Flotec might not work so well--too bad, so sad).

    That is an enormous lint filter just above the standpipe. From what I understand, washing machines are not typically manufactured with lint traps anymore. In our previous residence we had a grandfathered setup with a utility sink that drained to a floor drain system. We don't know really know where it went, just that it went at least twenty-five feet beyond the house's outlet drain grate and was clear based on a drain line check. We'd just used old nylons on the washer outlet hose to minimize lint accumulation in the drain.

    The same approach with a mesh lint screen in the neck of the standpipe in our current residence did not work. The standpipe overflowed many times (though the Flotec did run) before my wife and I concluded that even a small amount of lint accumulation within the screen in the standpipe would result in slow drainage and an overflow. We initially blamed the Flotec configuration and water backups for the overflow, but the removal of the screen and vastly improved drainage and water pump out proved that the link screen in the standpipe was the culprit.

    The standpipe discharges into the Flotec, so it's not good to allow unrestricted flow of lint and hair. From what I've read it seems this is a bad idea no matter how your washer discharges, even if directly into a municipal wastewater line. The drain protection product listed in our Whirlpool owner manual is (a) apparently discontinued and (b) rather ineffective based on reviews I read. What to do then? Read a lot more and settle on the Filtrol 160 (see I've just installed it, so we'll see how it performs, but we have to do something to trap the lint and hair.

    Thanks also for the recommendation about the conditioning system discharge tubing. I do wonder now why the plumber that installed that didn't just drain it through a trap and into the Flotec, too. It's probably not high enough to drain directly to the sewer line, as they are at just about the same height at that point in the basement. The sewer line drops down a few feet toward the front of the house before exiting, but that's pretty far from the conditioning cartridges on the joist. Maybe we can just have the whole thing moved and drain into the sewer, but at least we know this setup is probably wrong, too. I'm guessing it was, again, speed, convenience, and cost at the expense of a questionable installation.

    Thank you.
  5. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    In addition to hooking up a proper vent, there are some other possibilities.

    1. That pump only serves the laundry. Remove the AAV, and treat this pump chamber as a not-sealed system.
    2. Put a 2-inch standpipe up higher so that the WM discharges near the ceiling. The standpipe, with AAV, discharges into the sewer line several feet above the floor, so no extra pump is need. Most WMs can pump up to 96 inches from the floor. There are extension hoses sold.

    I am not a pro. #2 standpipe would meet IPC code, because IPC is more flexible about how high a laundry standpipe can be vs UPC. Laundry into non-sealed sump? I don't know. Temporarily removing the AAV, should work around the problem, and it would be easy to return to what the local inspection permitted.
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