Bathroom Remodel DWV Layout

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by FLJeff, Jan 2, 2012.

  1. FLJeff

    FLJeff New Member

    Messages:
    9
    Location:
    Central Florida
    Hello,

    I am just finishing the tear-down phase of a master bath remodel. This bathroom had a tiled alcove shower and a toilet. Just outside the door (to the right in the photos) is a double vanity. The house is slab-on-grade.

    I have a bit of a problem with the new DWV layout.

    The existing 2" shower drain is only 16" from the wet wall. It is a bit odd in that it has no trap directly under the drain. It disappears under some inaccessible slab so there may be a running trap under there. It then takes a 90-degree right turn and expands to 3" with a vented tee. Almost immediately afterward, the toilet drain intersects with a wye and the 3" drain continues under the wall behind the double vanity. The double vanity has a drain and vent for each sink that presumably drain into this line. The first vent/drain stack from the vanity is only about 18" from the right wall in the photo. All of the vents are 2".

    The new toilet drain is to be about 4" to the right of where the existing vent penetrates the slab (in-wall toilet).

    The new shower drain is to be centered in the 5'x3' shower alcove space.

    The vent cannot be within 16" on either side of the new toilet drain due to the in-wall toilet frame (and framing). I cannot easily move it to the left because the wall becomes an outside wall right where the insulation begins. The slab also gets thicker just to the left of the existing vent. I would really like to avoid having to break this section of the slab. Thankfully this wet wall is not load bearing.

    My current plan is to abandon the existing inaccessible shower drain pipe. I will move the vent to the right by 24" to leave room for the in-wall toilet framing. The shower drain will run diagonally from the center of the square-ish cutout across where the existing toilet flange is and join the drain line with a wye.

    The problem is that this configuration makes my shower arm about 66" from shower drain center to the vent. Based on what I have read, I have seen 2" trap arm maximum distances ranging from 60" to 96". Florida's building code specifies 8'. Will I be safe from trap siphoning with this long trap arm?

    Because the vent is coming down the wall, I can't vent the shower drain line until it joins with the under-wall line. This means I have to either vent this line after the toilet and either just before or just after the shower line joins it. All of these fittings will be quite close to one another, so I am not sure how much the order matters. Is there such a fitting as a wye with a vent port on top to vent it right at the intersection? Is it OK to have the toilet draining past the shower?

    I am open to suggestions if there is a better way. Worst case, I could break up more of the slab and sole plate to move the vent leftward. I really don't mind doing the extra work if my lazier solution could possibly cause trouble.

    Thank you.
    shower_wall.jpg toilet_wall.jpg
    shower_floor.jpg toilet_floor.jpg
    toilet_floor_proposed.jpg
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
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    Location:
    Land of Cheese
    Last edited by a moderator: Jan 24, 2012
  3. FLJeff

    FLJeff New Member

    Messages:
    9
    Location:
    Central Florida
    Thanks for the quick reply.

    The shower will have a glass door. No room for a vent there.

    What exactly is the precise definition of "trap arm" here? Is it simply all the piping between the trap and the nearest vent? In the existing setup, that would that mean the shower trap arm ends at the vent just before the toilet wye. If this is the case, then we're only talking about a matter of several inches between the vent being in or out of the trap arm.

    If I slightly modified my proposed solution to have the shower drain intersect the vent just before it joined the toilet drain, would that make it OK? To me it doesn't seem much different. I can imagine that it might do a bit more to prevent a large slug of flush water from getting between the shower arm and the vent. Couldn't that few inches just be called a wet vent? Or is that not possible because the toilet is a special case?

    If I were starting from scratch, I think I would vent it in the nearest wall to the drain, then make the 90 degree turn to meet the toilet line. I'm just trying to work with the existing slab holes if possible.

    Thanks again for the help
  4. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Maybe I am missing something? How can this possibly fly as we see it......where is the trap????
  5. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,246
    Location:
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    The minimum requirement is that the trap and drain must be 2" and the maximum distance between the trap and vent is 8 feet. The trap arm is the horizontal pipe leaving the trap. It must be pitched 1/4" per foot between the trap and vent. No other fixtures can drain into the trap arm. A wye and 45 combo should be used to cause the vent to rise vertically from the trap arm.

    The entire text of the 2007 Florida Plumbing Code can be downloaded online.
    http://www2.iccsafe.org/states/florida2007finaldraft/plumbing/PDFs/07Florida Plumbing Code.pdf
  6. FLJeff

    FLJeff New Member

    Messages:
    9
    Location:
    Central Florida
    Yeah I thought the same thing. Either there isn't one, or it has a running trap covered by slab. Not sure what they were thinking.
  7. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,246
    Location:
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    Don't overlook the simple fact that the trap arm can be routed to the side wall or back wall of the shower for the vent to take-off. The pitch must be maintained, but it does not have to be a straight line
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,626
    Location:
    Cave Creek, Arizona
    dwv

    That shower drain appears to be a floor drain with an integral trap. I have almost no concept of how you intend to do the piping, based on your description. The shower MUST have a vent before it connects to the toilet line. That vent can also vent the toilet, but a vent at the toilet would NOT vent the shower.
    Last edited: Jan 3, 2012
  9. FLJeff

    FLJeff New Member

    Messages:
    9
    Location:
    Central Florida
    I have drawn up a new layout based on what I have read here. The vents attach using T/Y combos as well.

    What do you think?

    Thanks

    dwv.jpg
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,626
    Location:
    Cave Creek, Arizona
    The 2" vent by the toilet serves NO purpose and is strictly cosmetic.
  11. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,246
    Location:
    Land of Cheese
    Progress is good.

    Are you installing a wall mounted water closet?

    If not, I would run the 3" diagonally from the closet bend and use a wye to connect the shower drain to the 3"

    According to the Florida code, the water closet can be wet vented by the shower vent, so you should not need the separate vent for the water closet.
  12. FLJeff

    FLJeff New Member

    Messages:
    9
    Location:
    Central Florida
    Yes, a wall mount toilet.

    I wasn't sure about the vent after the toilet. hj says it is pointless, I can see why that would be.

    So the extra vent really buys me nothing at all? I guess I understand the rules for toilets the least! I read somewhere that they might flush better with less venting to get a siphon effect.
  13. FLJeff

    FLJeff New Member

    Messages:
    9
    Location:
    Central Florida
    Digging Deeper

    I went ahead and removed more concrete to expose the rest of the shower drain pipe. It was a pain as the pipe passed right through the middle of a corner area of the foundation footer. You can see the exposed re-bar in the photos.

    I guess now we know where the trap was hiding! My guess is that this was originally a bathtub, later modified to make it a walk-in shower. They removed just enough concrete to plumb a drain line from the new drain location to the old trap. They didn't have enough vertical drop to put the drain in the center of the shower, so they ran it as far as they could while maintaining the slope. It looks to me like the existing trap wastes quite a bit of vertical drop that would have made a better drain location possible.

    The bad news is that the shower trap arm pipe was seemingly not sloped properly. It may have even sloped toward the shower a bit. It had almost a quarter inch of brown soil caking the bottom of it. Given its proximity to the toilet and its lack of resemblance to anything I have ever seen go down the shower drain, I must assume the worst! I am glad all of this is being replaced.

    CRW_1901.jpg CRW_1902.jpg
    Last edited: Jan 23, 2012
  14. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Good thing you exposed that mess, now get out the sawzall and start over.
  15. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,246
    Location:
    Land of Cheese
    Not sure why you hacked it out if you were planning to run a new branch anyway.
    If you accidentally crack the footing, the entire house could be affected.


    The 2" going into 1-1/2" is a classic DIY mistake.
  16. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Really?

    When was the last time you actually busted up some concrete, I think the dust got to your brain.
  17. FLJeff

    FLJeff New Member

    Messages:
    9
    Location:
    Central Florida
    I didn't even notice the 1-1/2" section! Even worse.

    The extra concrete had to go because I needed room for the new branch. It needs to go to the wall with enough room left over to run the vent line before I get to the in-wall toilet framing. I did a little extra because I was so close to removing the old pipe entirely. I also wanted to make sure I didn't have to rent a demolition hammer a fourth time!

    I fortunately chipped in deep enough to see the second re-bar. I was a little worried the inspector wouldn't like only seeing one.
  18. cad-cat

    cad-cat plumber/piping designer

    Was there a bath tub there at one time, maybe thats why its bushed down to 1 1/2". that would also explain them running over to the shower the way they did.
  19. FLJeff

    FLJeff New Member

    Messages:
    9
    Location:
    Central Florida
    I measured the slope on the shower trap arm and it was indeed sloped the wrong way - At 1/2" per foot to boot!

    The 3" part of the system was just barely 1/4" per foot in the right direction.

    It makes me wonder if during the original construction they ran out of space for slope and just fudged it to fit. The shower drain is the high end of the system.

    Here is a nice link to Bert Polk's plumbing tips
    Last edited by a moderator: Jan 24, 2012
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