Where does the P-trap go?

Discussion in 'Shower & bathtub Forum & Blog' started by blackm3sedan, Dec 6, 2011.

  1. blackm3sedan

    blackm3sedan New Member

    Messages:
    10
    Location:
    Orlando, FL
    It may seem like a simple question, but how do I put a p-trap in here without making it into an s-trap?
    [​IMG]

    It's a room addition which required a new slab and footing to be poured. I think the rough-in drain line should have been installed in the wall cavity and not in front of it. In this picture, the sink is on the left, which will have the vent, with the toilet in the middle and the problem bathtub drain on the right.
    [​IMG]

    Any suggestions?
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    You will need to do some digging. You need a tee on the white vertical pipe. The min. distance from the trap to the vertical pipe is about one pipe diameter, so as long as you can fit the tee in and connect the trap waste arm to it, you will meet minimum length almost just by definition.
  3. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    so there's no vent on the tub? is this why you're concerned about an S-trap, that you'll be cutting the rough in line down to the trap level with no vent on it? I'm not sure you can do that w/o creating an S-trap. If you can't connect that vent line over into the other vent, you may have to put in an AAV or something, but I'm not sure... hopefully jimbo or someone else with more experience than me will chime back in.

    In looking at it a second time... is there a trap buried in the rough-in? I didn't see that at first... if so, then i think you just need to offset the pvc drain line with a couple 45s and drop the tub drain straight into a 1 1/2" trap adapter, but again, maybe a plumber can verify that this is a legal setup...
    Last edited: Dec 6, 2011
  4. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    You're going to have to pull the tub back out and you might even need to chip some of the concrete away to allow yourself room enough to put a T in that pvc.
  5. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    Can someone explain to me why we're putting a Tee into the vertical PVC? Or a P-trap at all? Am I seeing the picture wrong, or is that PVC drain not vented and there's already a trap below grade?

    If its possible to extend that PVC up and tie it into the vent, its probably a good idea, if not code required (someone else can chime in on that, I never do shared vents... don't know the code for them). Then you'd need a Tee to tie in the drain and get a vent.
  6. dlarrivee

    dlarrivee New Member

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    1,172
    Location:
    Canada
    He asked how to connect a p-trap without creating an s-trap...
  7. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,236
    Location:
    Land of Cheese

    We cannot see if there is a trap on the bottom of that riser. If there is, then the installer failed to install a proper vent for the tub.

    If there is not, then a sanitary tee will need to be cut into the vertical pipe so that the trap can be installed and the vent can continue upwards.
  8. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    So unless I'm seeing the picture wrong (there's no vent on the tub line and there's already a trap below grade), let me rephrase...

    Why are we telling the OP to put 2 traps on a drain line, and then leave an open top on a Tee?


    Edit: Previous post was posted while I was typing, didn't see it until after posting reply.
  9. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    What is so confusing for you? Who said that there was already a trap?

    The original poster wants to know how to install a trap, why would he be asking if there already was one?
  10. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    I did. Look at the picture. Its not possible to be sure from this picture, but I'd say its 80% chance that there's a trap buried in there. I've said twice (and now 3 times), to correct me if i'm wrong, but the picture sure looks like there's a trap. What's so confusing about this statement? I know the OP said he's adding a trap, I always look at the pictures to confirm, and I'm doubting the need for one, so it seems imprudent to advise how to add a 2nd trap before determining that there is in fact not one already there, as it appears.

    There is also apparently no vent on the tub... the picture clearly shows 1 vent and the tub line is just a stub-out. I won't advise on the legality of this setup, as I don't ever do this (I vent every fixture), but that seems to be the situation. Therefore, advising a Tee makes no sense w/o determining that there is in fact to be a vent. The OP even said that the vent (indicating only one) was on the sink.

    This rough-in looks like a 2" lav vent wet venting the tub, with a PVC trap buried below grade on the tub. The reason the rough in is not in the wall is that the tub is meant to drain straight down into the rough in. Its a bit off though, so I think all that is needed is 2 45s to offset the line a bit, and a trap adapter to accept a tailpiece.

    Please correct me if I'm wrong on any of this, but I don't see the point in advising someone based on what they asked when the pictures seem to show otherwise.
  11. blackm3sedan

    blackm3sedan New Member

    Messages:
    10
    Location:
    Orlando, FL
    I'm not sure if there is a trap at the bottom of the riser. I should have taken better pictures, but at the time, I was just thinking of documenting where the pipes are run and not what they looked like.

    I thought it would be a bad idea and and very unusual to bury the trap in the 20" thick footer, so I'm assuming it's not there. If the trap is there, then I doubt it meets my plumbing code for having the trap within 24" vertical distance of the fixture drain. I'm trying to get the 'licensed" plumber that did the install to come back out and take a look at it, but I'm getting the run around from him. He claims his company doesn't do rough-in plumbing work and didn't do my install. I only believe one of those statements.

    It's going to be difficult to vent that fixture without using an AAV. The bathroom is installed under a nearly flat roof, only 6 degree pitch, and the tub installs in the lowest corner of the roof. I'd have to put an access panel for the AAV on the outside wall, since it would be behind the shower wall. But I hate even more the idea of putting a vent through a flat roof.

    Since the sink is tee'd into the main line before the tub is, doesn't that also vent the tub? The vacuum created by the toilet flush will be relieved as it passes the tee for the sink and should prevent it from pulling water out of the p-trap. The overflow for the tub should also vent that line also, even if it's not recognized by code.
    Last edited: Dec 7, 2011
  12. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Thank you for staying with us on this. I can't tell from the angles of your photos if there is sufficient height for the trap to already be there. Frankly, it would have been "usual" for the plumber to put one there. You need to dig down deeper in that tub box to find out whats what.

    What's wrong with a vent on a flat roof? I think FL is under the IPC which apparently would allow an AAV. Under the UPC inspectors often do not allow an AAV just to make your life easier! They insist on proper venting.
  13. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,236
    Location:
    Land of Cheese
    This isn't rocket science- pour water down the standpipe and shine a flashlight down to see if there is a trap holding water. If there is not a trap, the line will drain clear.

    The overflow is ahead of the trap, and does nothing to prevent the trap from being siphoned.
    Last edited: Dec 7, 2011
  14. blackm3sedan

    blackm3sedan New Member

    Messages:
    10
    Location:
    Orlando, FL
    Hey, easy on the rocket science stuff. I work for NASA. ;)

    Now that you mention it, there is water in the bottom of the riser. But I also know the small tank is full of water, because I tried to move it. I'll get power to the pump to clear it and see if the water is still there.

    So if there is a trap at the bottom of the riser, then all I have to do is connect the white pipe to the black pipe, right?

    Am I going to have problems in the future with the trap being lower than 24" beneath the fixture drain, assuming the inspector doesn't catch it? Is that some silly code requirement with no technical reason for it?
  15. blackm3sedan

    blackm3sedan New Member

    Messages:
    10
    Location:
    Orlando, FL
    Well it does appear that there is a trap at the bottom of the riser. Either that or it's sloped the wrong way. There is definitely water sitting in the bottom of the riser after the pump is activated. I guess the only way to be sure is to dig it up, hoping that it's not buried in the footer.

    So am I ok in just connecting the tub to the riser without a trap. Do I NEED a vent? I was a little worried about slow draining without the vent, but I think the overflow should be enough of a vent for that (which is what I meant in my previous post).
  16. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Wow.

    The overflow on the tub is NOT a vent. It's UPSTREAM of the trap.
  17. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,226
    Location:
    Cave Creek, Arizona
    Your picture shows EVERYTHING except the most important thing which is the fitting at the bottom of the tub riser pipe. IF there is a trap, which could be WHY the pipe is in front of the wall and not inside it, then you have BIG problem because the tub is not vented AND the toilet water flushes PAST the tub connection to the main line. IF it does NOT have a trap, and there is no way to determine that until the water is pumped out of the basin, then that 1 1/2" riser pipe has to become a vent and you have to make a trap connection somehow.
  18. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    Can you get access to a camera snake? I have a Ridgid See Snake Micro (about $200, a very fun and convenient tool), that will let me take a look down a line like that up to 6'. This would be a much less invasive way to check if there is a trap or not. If you have standing water and there isn't a trap, you've got bigger problems... time to get a jackhammer...

    A vent's function has almost nothing to do with making the line flow better, but to prevent siphoning of the trap. An unvented line will drain quite well, a bit too well in fact, and you'll have no water left to seal off the sewer gases. You have no way to add a vent if there's a trap down there other than to start digging. Adding one before the trap will do nothing for you.

    I think that you would be functionally fine to just connect down with 2 45s if there is a trap... again, I can't say if it would pass code or not, but guessing not based on hj's comments. But, I think that the sink wet vent would functionally relieve the pressure from the toilet and prevent siphoning. Not sure how inspection will go for you on that though...

    Determine what's at the bottom of that line for sure one way or another... that's step one before anything else can be definitively figured out.
  19. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,226
    Location:
    Cave Creek, Arizona
    There is nothing wrong with installing two 45s in the riser, regardless of whether it is a drain or a vent. The "sink wet vent" does NOTHING to prevent the toilet from affecting the tub's trap. IF you have something "flexible" such as a metal tape measure, slide it down the pipe as far as it will go. IF it goes around the corner, there is NO trap. IF it gets stuck at the bottom, then there PROBABLY is a trap, but it could be inconclusive since the ruler could get stuck where the pipe enters an elbow.
  20. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    Does the toilet really create that much suction these days? I'm not challenging your knowledge hj, you obviously know a lot more about this than I do, just asking. It seems to me that today's 1.6 GPF max toilets wouldn't fill up the 3" line enough to seal off the side inlet from the tub, thereby not creating much of a suction force on that tub line if there's a 2" vent freely available to draw air from right next to it... But I don't really know, just theorizing...

    As I said earlier, I don't believe in shared vents, I vent every fixture, every time (other than wet-venting a toilet off the main stack if its w/in 6'), so its not really an issue for me. But given this situation, wondering if the OP can't just get by with dropping the tub drain "straight" in with 45s and letting the toilet vent off of the sink, even though its not a technically legal setup. I wouldn't advocate setting it up this way, but if it will work well enough, I'm not sure I would advocate digging all that concrete up to change it either...
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