trap alternative

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by foghat35, Jul 11, 2007.

  1. foghat35

    foghat35 New Member

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    Hello all. I'm replacing a sink in a downstairs bath. It has a s-trap that I'm also replacing. Is there any alternative to an s-trap besides a p-trap?? A p-trap is not possible in this situation. thanks
  2. Gary Swart

    Gary Swart In the Trades

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    You have to find a way to use a P trap, that's all there is that is code. S traps are illegal, and the drain must be trapped. Perhaps I haven't go the whole picture, but if you are removing an S trap, why won't a P trap fit in the same space?
  3. foghat35

    foghat35 New Member

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    I can't send a pic but this is easy to understand. This is a tiny bathroom. By tiny I'm talking 10 sq ft. The origional sink is only 15.5 x 12.5" deep and the pipes come up through the floor right beneath it. The drain pipe is only 4" inches from the wall. It's so tight that the s-trap is folded into a loop and is parallel to the wall. I was originally going to repipe the drain up through the wall but it's on top of sistered joist with the concrete basement wall under that. There isn't any other way to run the pipe. This might be hard to follow but the only thing I could come up with is to put a 45° elbow on the pipe where it comes up through the floor, then pipe into the wall and use another 45 to pipe up through the wall with a quarter bend out to the p-trap. Then just figure out some decorative scheme to cover the pipe. How far from code would that be?:D
  4. frenchie

    frenchie Jack of all trades

    I know it's not code, but in those circumstances I'd leave the S.

    Oops, did I say that out loud?

    If it self-siphons a lot, I'd turn down the pressure on the sink supply lines at the cutoffs, so there isn't enough water flow to self-siphon it.

    It ain't the right way to do it, but sometimes you're best off just making do...
  5. foghat35

    foghat35 New Member

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    Come to think of it, isn't it true that the only reason s-traps are still available is for replacement in older homes that had them as part of the original plumbing?
  6. S to P with AAV

    some people signed in here have converted S traps into P traps by adding an AAV. The advantage is that doing so allows all the same pipe geometry to stay as it was before.

    I'm not sure if I follow the mental picture your words described, about the 45 degree bends, and I'm not sure where you have venting in that picture... i think you haven't mentioned venting yet.

    The difference between a P trap and an S trap is entirely in the fact that a P trap connects to a vented - vented- stack, in a geometry / configuration like a P laid sideways. The right fitting is a Sanitary Tee which connects the J shaped part of the P trap to the vented stack. Not a Straight Tee fitting, not a Wye fitting, and not a Combo fitting.

    The definition of an S trap is that there is no venting after the J shaped part of the trap, so waste water going down a vertical pipe causes problems to that water seal above or to other water seals elsewhere close by.

    Adding a Studor / AAV -- to a rebuilt S trap using a Sanitary Tee fitting -- adds enough venting to a hand rinse sink to do a great job of venting that new P trap, so it doesn't risk being sucked dry either by itself or by any other fixture nearby. But beware -- AAVs cannot be used as a solution all over the house. One only, at a low flow fixture, assuming there is plenty of real venting elsewhere, etc.

    whew.

    Where is your vent?

    David
    Last edited: Jul 11, 2007
  7. foghat35

    foghat35 New Member

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    The vent situation I hadn't figured out yet. I wanted to try and fit an aav in somewhere. Rebuilding a s-trap with a vent would be great if I could do it with chromed brass.
  8. only with venting.

    all people posting above are assuming you have a "stack" and a vent. That is the only way to get a P trap.

    Any other way makes an S trap, either one that looks like the letter S or one that acts like an S trap anyway even though it looks a little different from an S. The term 3/4 S trap has sometimes been used to describe situations where a Wye or Combo fitting is used instead of a San Tee because it is almost a full S configuration but it looks like it is only 3/4 as bad.

    The first question is where the vent is.

    David
  9. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Any P-trap without a vent is an S-trap.
    a mechanical / Studor vent is the easiest fix, not legal in some states
  10. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    The biggest problem is suction when the toilet flushes...once a little flow is intiated from that..siphonage takes over..
    As for your disregard for code, you will be punished in the afterlife...40 lashes with a wet noodle.
  11. frenchie

    frenchie Jack of all trades

    That makes a lot of sense.

    Just sayin' - I've seen more than a few old houses with S-traps. Even though they aren't supposed to work, sometimes they do. Maybe because there's enough air getting into the system elsewhere? I don't know; but I have seen them work okay.

    If it ain't broke, don't fix it?

    Especially if it's a nightmare to revent... (and it sounds like it).


    Cool trick with the AAV, Genie; I never would have thought of that... but then I've never seen an actual AAV, only heard of them & seen pics.

    I guess NYC must be one of the places that doesn't allow them.
    Last edited: Jul 12, 2007
  12. dubldare

    dubldare Plumber/Gasfitter

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    MN/ND
    MN and ND prohibit them as well.
  13. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    I VERY often wind up getting called to repair leaky drains, or replace a faucet with S-traps...most often dropping down below the floor on converted cottages (usually well over the 24" inch tailpiece rule to get below the joists and noticeably larger numbers of deoderizer sprays in the vicinity)
    Obviously there's NO way around it...unless I can somehow convince them that ripping out walls/ceilings for thousands is a good idea.
    As for Mechanical vents...not legal here either. (leaving us with the option of ripping walls apart...yeah, it could happen).
  14. prashster

    prashster New Member

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    If it were me (not a pro) I'd leave it as an S. It's not like you're gonna be any worse off than you are now. If it ain't broke, why fix it now? If it 'sucks' then replacing it later won't cost you any more than replacing it now.

    For proactive kicks, I'd find out a) if yr town permits AAV's, and b) if someone makes a chrome AAV. Heck, you could always spray some rustoleum on a studor!!!

    I saw these in London:

    http://www.studor.net/products/trap-vent_UK.asp


    Wish they flew here.
    Last edited: Jul 13, 2007
  15. Peanut9199

    Peanut9199 Customer Service Manager Plumbing Wholesale

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    Last edited by a moderator: Apr 30, 2010
  16. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    A P-trap becomes an S-trap when there is no vent.
    A P-trap needs to be at least 2 pipe diameters away from the vent to the trap weir (water in trap).
    The S-traps in your link would likely become P-traps IF they had a vent tied into the back side where the drain drops.
  17. Laurieg

    Laurieg New Member

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    Location:
    florida
    OK here's my question...my bathroom is on the second floor the drain goes to a stack. But I want to move the sink. Can I use an "S" trap running to the drain under the floor?

    [​IMG]
    Last edited by a moderator: Apr 30, 2010
  18. hj

    hj Moderator & Master Plumber Staff Member

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    An "S" trap with an AAV, and a "P" trap with an AAV are NOT the same. The only way to install a "vent" on an "S" trap is by using a "crown vent" and that is illegal. A "P" trap with an AAV, will NOT be in chrome, and it will require more space than your configuration gives you, unless you also offset the riser sideways from the sink drain.
  19. thebigsee

    thebigsee DIY Member

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    Location:
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    Either leave it be or tear it all out and start over and do it right -- preferably the latter. I've tried monkeying around with easy fixes to major problems and it always just cost me headaches and maybe even more money in terms of time and materials. Once I did it right and solved the problem, that's when I would say, "I should have done that years ago."
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