I'm in the process of moving our laundry area from inside the house to the garage. I'm not going to dismantle the old washer drain stack or plumbing, as future owners may want to relocate the laundry back--plus, well, that's just extra work I don't want to deal with.

The problem is the current washer drain stand pipe. If it's not in use, the p-trap will eventually evaporate, plus I have a hunch that it may not be properly vented in the first place (we sometimes get a strange odor from it).

What's the best way to plug this pipe non-permanently? The catch is that since it's part of a washer box (where the drain and faucets are integrated) there's no outside to the pipe for me to add a proper cap. Would a rubber cork suffice if I find one the right diameter? Or some other DIY technique? One thought I had was a water balloon...but that seems imperfect. :)

  • Rubber stopper with compression screw would work. Better would be to affix a real plumbing end-cap to the pipe; you can always remove it later to return that drain to active use.
    – keshlam
    Commented Mar 23, 2015 at 18:14
  • @keshlam the catch is I can't add an actual cap. The pipe is integrated into the bottom of the washer hook-up box, so there's no outside edge to the pipe. The rubber stopper with compression screw is a good idea, though!
    – DA01
    Commented Mar 23, 2015 at 18:41
  • As per some previous answer I'm not looking up right now, put some RV antifreeze down the pipe before sealing - it will keep the trap full for a longer period of time than just water, and that serves as insurance if the test plug is not "perfectly sealed."
    – Ecnerwal
    Commented Mar 23, 2015 at 20:43

1 Answer 1


You should be able to find caps that just pop on, or in the pipe.

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Or you could get a test plug, if you really want.

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(source: petersenproducts.com)

  • so they exist! Perfect. Will do some googling for the size I need.
    – DA01
    Commented Mar 23, 2015 at 18:42
  • 1
    @DA01 the test plug (the one with the wingnut) is the only one I would recommend. It keeps an airtight seal for a long time and it is totally removable if you want to use the pipe again. Commented Mar 23, 2015 at 20:13

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