We're moving our washer from our current location (hallways closet) out to the garage. To do this, I need to put in a new standpipe and drain in the garage.

The ideal junction for the new drain (green line) into the main would be in a spot that's currently a rats nest (red circled area) of various pipes. There's the drain, but also various hot/cold water lines, a gas line and heating ducts. Kind of a nightmare.

So it looks like it'd be a lot easier to have the drain go past that mess then 'u-turn' back into the existing drain for the washer. The added bonus is I'd also have better slope by tapping into that point.

Is there any reason why this shouldn't work? Is there some law of drain physics I'm not aware of that frowns upon u-turns?

Sketch (top view of the crawlspace drains):

enter image description here

  • @TylerDurden ha! depends on the hemisphere, though! :)
    – DA01
    Feb 17 '15 at 2:32
  • @ChiefTwoPencils I hope we don't have much poop in our washer! :)
    – DA01
    Feb 17 '15 at 3:31
  • The length of the run will matter, if there's no vent before where it ties in.
    – Tester101
    Feb 17 '15 at 10:08
  • @Tester101 there will be a vent right after the P trap at the new washer location. Total run is maybe...15' (green line).
    – DA01
    Feb 17 '15 at 17:30

With plumbing it is all about maintaining the proper drop per foot. The fact that this is a wash machine makes the call even easier. I guess the theoretical issue would be would the 90s and slowing of the water make it more likely that something could stick to the inside bend and accumulate enough that you would have an issue. My thoughts on this:

  • don't see what would stick to PVC from a wash machine
  • use long sweep 90s so you don't have sharp bends
  • and if this ever did fail you would have easy access to it

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