Crown-Vented Laundry Drain Trap?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by inspectordan, Sep 22, 2012.

  1. inspectordan

    inspectordan New Member

    Messages:
    1
    Location:
    Chicago
    Hi All....great forum! I hope I'm not embarrassing myself by asking but does this laundry drain constitute an improper crown-vented trap or any other defective drain/trap? Thanks!

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  2. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    Yes the stand pipe must not have any off sets.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    NO. It is done like that anytime there is not room in the stud space for the trap and wall box to fit with a straight riser. How else COULD you do it? A box with the outlet offset to the side would help, but they are not that easy to locate. Don't sweat it.
  4. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,175
    Location:
    Maine
    You need twice the pipe diameter between the trap elbow and the sanitary tee inlet.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    I would say he has about that much center to center, and I have never had an inspector turn down an installation like this one. What do you want him to do, remodel the wall to give more room between the brick and the stud?
  6. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    The measurement is taken from the crown weir to the opening in the tee. In that situation the inspector is likely to overlook it.
  7. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,175
    Location:
    Maine
    It's an S trap. Every inspector in a 200 mile radius of here would make him change it. You do what needs to be done to meet code.
  8. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    Actually he could remove/relocate that stud on the left side to give him the required 2x trap arm required. The offset in the riser is OK as long as the p-trap is set level.
  9. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    The "2x diameter" rule does not mean you need 4 inches between the hubs of the fittings. And I may be a little dizzy on chemo, but I don't really see where this is an S-trap.
  10. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,175
    Location:
    Maine
    CrownVent.jpg

    You need 2 x the pipe diameter between the weir of the trap and the inlet of the tee. What is there ain't even close. It's an S trap with a vent that does nothing to break the siphon. That trap will siphon.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    quote; It's an S trap

    That is the most ridiculous statement ever posted here. There is nothing that even approximates an "S" trap in the installation, and it is EXACTLY like thousands, probably tens of thousands, of washer drain installations, with or without the offset in the riser.
  12. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,175
    Location:
    Maine
    You need to get the code book out and do some reading. I do agree though that there are thousands of them out there just like that and every one of them is ........wrong. How can yo look at that and not see an S trap? If it's because of the vent then again, read the code book.
  13. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    I already said it means from the crown weir of the trap to the opening in the san tee. The hubs have nothing to do with it. The same requirement applies to hubless pipe and fittings.
  14. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,175
    Location:
    Maine
    CrownVent.jpg ..........................................
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    That is really stretching things to make it an "S" trap. Using that logic, EVERY "P" trap would be an "S" trap if you turn it on its side. You obviously do NOT know the dynamics of a siphon, which a "TRUE S TRAP" uses to be illegal, nor how a vent works. But then, when you turn a P trap on its side, like your drawing, then there is NO trap at all in the drain. Time for you do some remedial classwork, by taking Plumbing 099.
    Last edited: Sep 23, 2012
  16. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,175
    Location:
    Maine
    I turned the photo on it's side so that you could more clearly see the S configuration there. The 2x the pipe diameter from the weir to the inlet is what makes a P trap a P trap. Where the trap vents from is incidental. That trap in that configuration will siphon just fine with or without that vent. I have set that exact same thing up in the lab many many times using clear 2" PVC and fittings. given enough velocity (which a washer has) it siphons every time. Increase the weir to inlet by 2x pipe diameter or more and it never siphons. I can't think of a single plumbing code that will allow that configuration and again, there's not a plumbing inspector either state or local that would let that go around here including me.
  17. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    Thou dost protest too much. You are trying to justify the unjustifyible. You could not make that trap siphon even if you put a suction pump on the bottom of the drain riser. And that is how we tested traps and vents at the Chicago Cabrini Street Testing Laboratory. We did not just depend on gravity to create enough suction. And there are tens of thousands washer drains installed just like that and NONE fo them have "siphon problems", nor could they have them.
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