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Thread: trap alternative

  1. #1

    Default trap alternative

    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. #2
    In the Trades Gary Swart's Avatar
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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. #3

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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?

  4. #4
    Jack of all trades frenchie's Avatar
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    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. #5

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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. #6
    Homeowner geniescience's Avatar
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    Default 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 by geniescience; 07-11-2007 at 02:22 PM.

  7. #7

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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. #8
    Homeowner geniescience's Avatar
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    Default 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. #9
    Licensed Grump GrumpyPlumber's Avatar
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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
    "The biggest regrets we have in life are the chances we never took."

  10. #10
    Licensed Grump GrumpyPlumber's Avatar
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    Quote Originally Posted by frenchie
    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...

    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.
    "The biggest regrets we have in life are the chances we never took."

  11. #11
    Jack of all trades frenchie's Avatar
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    Quote Originally Posted by GrumpyPlumber

    The biggest problem is suction when the toilet flushes...once a little flow is intiated from that..siphonage takes over..
    That makes a lot of sense.

    As for your disregard for code, you will be punished in the afterlife...40 lashes with a wet noodle.
    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 by frenchie; 07-12-2007 at 03:12 PM.

  12. #12
    Plumber/Gasfitter dubldare's Avatar
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    MN and ND prohibit them as well.
    --Customers of plumbers: Never be afraid to ask for proof of licensure of the plumber servicing your equipment. A licensed plumber will be proud to show you his personal license.--

  13. #13
    Licensed Grump GrumpyPlumber's Avatar
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    Quote Originally Posted by frenchie
    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.
    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).
    "The biggest regrets we have in life are the chances we never took."

  14. #14

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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 by prashster; 07-13-2007 at 10:48 AM.
    (important note: I'm not a pro)

  15. #15
    Customer Service Manager Plumbing Wholesale Peanut9199's Avatar
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    This is a S/Trap
    exits out of the floor
    http://www.clawfootsupply.com/product415



    This is a P/Trap
    exits out of the wall
    http://www.clawfootsupply.com/product413



    How could you change the S/trap to a P/trap with a AAV unless you break the wall?
    Last edited by Terry; 04-30-2010 at 02:40 PM.

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