Tight space trap arm question

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by hdb, Sep 29, 2012.

  1. hdb

    hdb General Contractor

    Messages:
    6
    Location:
    Central Coast, California
    Good morning,

    While questions regarding trap arm length have been discussed, ironically, at length -- I'm wondering what you folks do to combat tight spacing. This installation was for a stacked washer dryer, and there wasn't much space to work with. I'm wondering what your interpretation is on the trap arm length. If you look at it from the radius bends, it's just under 4" (this is 2" pipe). I'm wondering if it meets the intent.

    IMG_1730.jpg
  2. hdb

    hdb General Contractor

    Messages:
    6
    Location:
    Central Coast, California
    And, by the way, the san t on its back was already changed out to a combo.
  3. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    The vent could have gone up inside the stud bay to the right of the washer setup, then you would have had plenty of room.
  4. hdb

    hdb General Contractor

    Messages:
    6
    Location:
    Central Coast, California
    That's a good point. I considered that; however, what you can't see is the framing above that which would have been prohibitive. I considered 45'ing over to it.
  5. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,271
    Location:
    Maine
    Not here it doesn't. The trap is an S trap or more commonly referred to as a 3/4 S trap and I don't know where the 2" lateral to the right goes but here that would have to be 3"
  6. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    I would rather have an offset vent than an offset standpipe and no trap arm.
  7. hdb

    hdb General Contractor

    Messages:
    6
    Location:
    Central Coast, California
    Hi Tom. I've read your points in previous posts regarding S traps and arm length. I understand what you're saying and appreciate your point. The 2" to the right is going to a utility sink, which is also vertically vented.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,060
    Location:
    Cave Creek, Arizona
    Anyone who calls THAT an "S" trap, (and it does not even come close to the definition of a "3/4 S" trap), has absolutely no concept of what constitutes an "S" trap. Your installation is no differnent than hundreds, if not thousands or ten thousands, done exactly like that for the same reason. Revising the drain line slightly and using a wall box with the drain at the left end would have made it LOOK prettier but would have done absolutely nothing to make it work better.
  9. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,271
    Location:
    Maine
    I know you don't believe it but you western plumbers must play by different rules because that don't pass anywhere in the Northeast. Not Maine, not NH, VT or even liberal Mass. Technically the vent sort of makes it not an strap but the piping arrangement does not meet the trap to inlet minimum. Put one together, get out the tape measure and check for yourself. I have failed literally hundreds just like that and so has every inspector in the region.
  10. kreemoweet

    kreemoweet Member

    Messages:
    375
    Location:
    Seattle. WA
    A "crown vent" I believe is what that is. It is clearly a violation according to the Uniform Plumbing Code, but it is widely overlooked by
    inspectors. Or there might be local libereralizations.
  11. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,271
    Location:
    Maine
    The vent take off is too far back to be considered a true crown vent but you are correct, it is a violation of every code that I know of and I am more than sure that plenty of inspectors overlook it as well but bad plumbing is bad plumbing. I call's them like I see's em
  12. hdb

    hdb General Contractor

    Messages:
    6
    Location:
    Central Coast, California
    I appreciate the feedback. The trap arm is 3". While I'm a stickler for code compliance and building correctly, 1" is a tough sell for reframing a 70 year old house. Rock lath and cement are no fun to deal with.
  13. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    If the distance from the crown weir of the trap to the opening in the pipe for the vent is less than 2 pipe diameters it is a crown vent, it need not be at the true crown of the trap. The combo picking up the W/B should have been cut in the next stud bay then run back to the standpipe. While not too many inspectors seem to harp on this issue (min trap arm distance) it is code, and for a reason.
  14. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    It doesn't appear that you are that much of a stickler, it could have been done correctly without reframing anything or dealing with any cement. Nor is a lack of convenience a valid reason for a code violation. While structural conditions play into an inspectors decision it is not applicable here because it could have easily been done to code by cutting in the fitting in the next stud bay and plumbing back to the standpipe. What load is that wall even picking up with that CMU wall right behind it?
  15. Terry

    Terry Administrator Staff Member

    Messages:
    15,314
    Location:
    Bothell, Washington
    My normal practice would have been to come up in the bay next to the box; not the same bay. That would have allowed for a longer trap arm, and elimated the need for the extra 45's.
  16. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Exactly, it would have been fewer fittings too.
  17. hdb

    hdb General Contractor

    Messages:
    6
    Location:
    Central Coast, California
    I agree. There's a header above that small bay to the right, and I can't penetrate through it for obvious reasons. What I can do... is exactly what you're saying -- moving the combo fitting into the right bay, and then venting up and eventually 45 the vent back in to the bay above the washer box. Thanks for the good points. I'll post a picture when I'm done.

    That wall isn't CMU, it's a product call rock lath. It was used, around here, during the 50's. It's a 1/2" gypsum board with holes in it, came in 16" widths. It was ran perpendicular, and then it was covered with 3/4" of concrete. Plaster was textured on top of that for the finished product. It's the in-between from lath and plaster to drywall.
  18. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,060
    Location:
    Cave Creek, Arizona
    quote; I have failed literally hundreds just like that and so has every inspector in the region.

    From that statment, I have to assume you are a city plumbing inspector, and if so, HOW can you not know what a 3/4 "S" trap is? When I was an apprentice, we had a neighboring city's plumbing inspector working for us. I fired him because he did not know what he was doing. When you got a few beers into him and asked him about apprentices, he would bemoan the fact that "He has been a plumber for 25 years, and some apprentice fired him".
    Last edited: Oct 1, 2012
  19. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,271
    Location:
    Maine
    I don't inspect anything anymore but that particular configuration has come to be known as a 3/4 S, why I can't tell you. Technically it is not, and neither is it a true S trap but it is an illegal trap because you need 2x the pipe diameter between the weir and the inlet and there ain't anything near 2 times the diameter there.
  20. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,060
    Location:
    Cave Creek, Arizona
    IT does not even approximate a 3/4 "S" trap, nor does it approximate an "S" trap. It is a "reach" to even consider it capable of siphoning under ANY condition.
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