45's to raise p-trap arm?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by vistaman, Dec 8, 2008.

  1. vistaman

    vistaman New Member

    Messages:
    35
    New vanity in a bathroom remodel has a cabinet floor that is several inches higher than the old vanity floor. It comes to just below the bottom of the drain outlet coming from the wall. Just enough room to run the horizontal trap arm and tighten the slip joint. The DWV is in the wall just beyond that. The DWV looks like 2" or more, the tee is 1 1/2, the trap arm fits into a 1 1/2 x 1 1/4 adapter.

    To install the p-trap from the lav drain normally, I'll have to really hack out the bottom of the vanity to accomodate the bottom of the p-trap before connecting it to the trap arm.

    Is there some other solution? Is it OK to use 1 1/4" 45's in the cabinet to raise the trap arm enough to allow the p-trap to fit without cutting into the cabinet base? Any other ideas that will help without forcing me to cut the new vanity base?

    Thanks...
  2. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    That would create an unvented s-trap.
    The right way would be to raise it in the wall.
  3. vistaman

    vistaman New Member

    Messages:
    35
    In this case, raising the drain tee in the wall is not the best solution for me. The walls are newly tiled wainscot. Cutting into it would be too tricky for me; and the other side of the wall doesn't have decent access to the DWV line :(

    From what you say, I'm guessing that /any/ downslope on the horiz trap arm would also be a form of s-trap? Is there a minimum length for the trap arm? If not, would it be OK to put the p-trap and [a very short] arm within an inch or so of the drain inlet?

    That way I could locate the cut for the bottom/bend of the p-trap near the back edge of the cabinet and run 2-45's from the tailpiece of the lav for some drain slope to the top of the p-trap (or simply 2-90's?). In this method, the "horizontal" trap arm would be just a short connector to the tee, and no s-trap is formed.

    If this isn't workable either, then I don't see any choice but to cut the vanity floor near the center and hope for a neat/trim fit. No fun here today :)

    Thanks...
  4. NHJeremy

    NHJeremy New Member

    Messages:
    5
    this may work?

    What type of tee is in the wall? If you can adapt to that, possibly with a 1.5 " female adapter, come out of the wall and 90 up. Put another sanitary tee vertically, come out of the top with an air admittance valve. Now retrap the lav as you would normally.
  5. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    Take a look into the connection in the wall.
    Is it an elbow that goes right and left, or is it a tee with a vertical pipe behind it?

    It would have been nice to get this right before the new wall.

    If the pipe is vertical any repair could be hidden by the vanity.
  6. vistaman

    vistaman New Member

    Messages:
    35
    How high does the AAD have to be? There isn't much height under the lav. The center line of the drain to bottom of lav is about 21".
  7. vistaman

    vistaman New Member

    Messages:
    35
    Hi Redwood. Yup you're right on that, should've fixed it properly before the tile guy did the wainscot wall. Poor planning, I didn't count on the new vanity floor being that much higher than the old one <grrr....>. Figured new vanity going where the old one was so I'd be OK. Anyway:

    I've found some pics of the other side of the wall near this drain outlet, and the drain line to this lav seems to be a short (about 12"-16"") 1-1/2" pvc horiz run to an elbow out to the lav. I say "seems to be" because all I can see is the DWV tee and the start of the horiz run towards this lav drain.

    So I was incorrect in my first post: the lav drain does not directly connect to the DWV line with a tee out. It is an elbow off a horiz run from the tee out of the DWV. Is there any way to fix this without going back to the tee and raising the tee? Even if I break into the tile behind the lav I won't be at the tee. I can't get at the tee without really messing up the wainscot'd wall outside the vanity to where the DWV stack would be.

    Seems anyt upslope I do that is upstream of the tee and downstream of the p-trap would effectively create an s-trap? If that is true it comes down to minimizing the cutting damage to the vanity floor. Can I do what I asked about before: notch out the back of the vanity floor to accomodate the p-trap at the wall-out, 2-45's to get to the tailpiece? Is that a workable and would it be effective?

    Thanks for helping...
  8. vistaman

    vistaman New Member

    Messages:
    35
    OK, found the picture of the other side of the lav wall I'm working on. The view here is the bathroom lav plumbing on that other side, the first bathroom that was remodeled 3 months ago. The bottom tee going out to the right is the horiz line that connects to an elbow that goes through the wall to the lav drain I'm working on. Confusing?:confused:

    Attached Files:

  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,139
    Location:
    New England
    If you cut that horizontal run and replace with a couple of 45's in it, you could raise it.
  10. vistaman

    vistaman New Member

    Messages:
    35
    Jim, that was close to what I was first asking: putting a pair of 45's at the outlet coming out of the wall, upstream of the elbow, downstream of the p-trap.

    Redwood responds that 45's downstream of the p-trap, before the tee, effectively create an s-trap, that I would have to raise the tee. Are you saying that the 45's would be OK? Even more confused:confused:

    Thanks...
  11. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    Maybe this picture will allow you to grasp the concept of the venting on a dirty arm like that. While the picture shows a correctly vented dirty arm on the left with a sani tee, on the right using a combo or wye and street 45 creates the s-trap effect. See how the flow of air along the top of the pipe is cut off when you drop too far. Using a couple of 45's will do that.

    [​IMG]
  12. NHJeremy

    NHJeremy New Member

    Messages:
    5
    vistaman if you 45 that lav arm at all , you will cut off the vent. what i said before will work fine, 90 right out of the wall and put a sanitary tee on the 90. The AAV needs to be only 4" above the top of the trap (maybe more depends on the manufacturer of the valve) so if you have 21" of play you should have plenty of space.

    This is the only way to do it legally, however if you are not being inspected, go ahead and 45 up. It will still drain fine.
  13. vistaman

    vistaman New Member

    Messages:
    35
    Thanks for the drawing Redwood. I see how the syphon effect would work on that setup. But what about 45's /before/ the p-trap? Out of the tailpiece to a pair of 45's then down into the p-trap, and level/horiz out to the elbow? Would that be a proper method?

    There is also the alternative that NHJeremy proposes which apparently will work.
  14. vistaman

    vistaman New Member

    Messages:
    35
    That's some good info and it sounds like a workable solution. I don't have to worry about inspection here, but I do want a reliable drain that won't suck the trap dry :)

    Are san-tees and aav's available in 1-1/4" sizes? The 1-1/2" drain out has already been fitted (by tile guy w/the red-stuff glue) with a 1-1/2 to 1-1/4 reducing fitting for the trap arm.

    Thanks for participating.
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,825
    Location:
    Cave Creek, Arizona
    drain

    You CANNOT use 45's ANYWHERE in the drain line before the vent connection. Your problem is that the original installer did not know how to install connections for two sinks back to back and therefore made one, the one you are working on, lower than the other side. IF he had been a good plumber the drains on both sides would be the same height and you would not have this problem. It could have been fixed when the wall was able to be opened. Now your best option is to cut a neat oval in the cabinet floor so the P trap can hang into it. OR maybe two circles with the P trap coming up from below.
  16. vistaman

    vistaman New Member

    Messages:
    35
    Thanks. That's a nice clear statement about no 45's anywhere. Is it also true for 90's? Can 90's be used before the p-trap? Will the San-Tee/AAV combo proposed for after the p-trap be a better choice?

    Sorry for beating this thing around, I'm just trying to get a pipe-fitting solution versus cutting a new pricey cabinet floor or busting into a lot of tile wall to do an extensive re-fitting of that existing "stacked tee" setup.

    About those stacked tees: there are over 900 units in this complex, most are 2 bath units, all apparently plumbed the same way. I've seen the insides of several neighbors walls and have seen the master plans. The lavs aren't quite back to back, they just use the same DWV line and share a common wall.

    They were all built over a couple of year period in the late 60's (maybe that explains the setup?). All plans and construction were approved and inspected by Hollywood Florida, which is not considered a very flexible group, then or now.

    I surely won't deny that the thing should have been addressed and planned better when the wall was open, but "who knew" :)
  17. Mario

    Mario Master Plumber

    Messages:
    18
    Location:
    Kansas
    Not sure if you're under the uniform plumbing code as is the case in my city or the international plumbing code, but I believe the final vent height when using an Air Admittance Valve needs to be extended above the flood level rim of the sink, not just 4 inches above the P-Trap.
    Always the vent loop ties back in to the vent stack above the flood level rim of the fixture, so I believe if you're going to use an AAV, it should also be above the flood level rim as well.
    Using the AAV will still save you tearing out the wall to install an inverted san-tee on the vent stack.
    Also check some cities don't allow using cheaper "auto-vents", but require the more expensive "studor-vent" type air admittance valves.

    [​IMG]
    Last edited by a moderator: Jun 15, 2009
  18. tjbaudio

    tjbaudio Sound and Light Suppervisor for a School District

    Messages:
    162
    Location:
    Wisconsin
    I thought you could use 45's above the trap as in the pic.


    To the OP, just cut the cabinet. However measure very carefully and really plan it out FIRST. I would use a hole saw to get a nice round edge and then cut to the sides.

    Attached Files:

  19. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Without opening up the wall there is no good way to do this, and no way to do it to code.
  20. Mario

    Mario Master Plumber

    Messages:
    18
    Location:
    Kansas
    I just got off the phone with a plumbing inspector just to be sure, and they said they would normally want the AAV to be installed above the flood level rim, but they do evaluate on a case by case basis as in an island sink situation where they might allow it to fit under the cabinet.
    I don't know if not tearing out your "newly tiled wainscot" would qualify for an exception but you could ask 'em.
    Last edited: Jun 15, 2009
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