Replacing tub with shower pan

Discussion in 'Shower & Bathtub Forum & Blog' started by marc4790, Jun 11, 2006.

  1. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Hello. I have removed the tub and am in the process of constructing walls for a walk-in shower. My plumbing question is:
    Do I need to install a P-trap to the existing tub drain below the slab or can I safely assume that a trap was installed when the tub was set? The 2 inch pipe seeems to comes straight up from a sand bed below the slab, but I can not see below unless I dig down into the saand below the slab. there is a 9 inch by 12 inch opening in the slab around the pipe.
    Thank you for sharing your time,
    marc
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    The tub surely had a trap. You have a problem here, in that the tub drain is 1½" and code requires 2" for the shower.
  3. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Replacing tub w/ showerpan

    Hi Jimbo, thanks for the reply. The drain is 2 inches. I measured it and bought two 45 degree ells and two inch pipe to bring it out away from the head wall.
    marc
    Last edited: Jun 11, 2006
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,134
    Location:
    New England
    The trap should be directly under the drain...
  5. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Trap in tub drain

    Thanks Jim. Should I dig out around the drain to find the trap? I did remove the one and a half section that was attached to the tub via an adapter or reducer from the two inch pipe that comes out of the ground below the slab. I cut the adapter that was glued onto the two inch pipe, just below the reducer, but now must raise the height aabove the slab and bring it out away from the wall to get it above the sloped deck that I will form in preparation for the membrane.
    marc
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,134
    Location:
    New England
    You'll probably have to break up some slab. Move the p-trap so it is under the center of your shower pan and you have the proper slope (1/4"/foot) back to the main line.
  7. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Replacing tub w/ showerpan

    Jim, is it necesaary to move it to the center, (that would mean moving it 3 feet instead of about 4 or 5 inches. Couldn't I just slope the bed to the end of the 33 inch by 56 incht shower stall? That would save a lot of work breaking through the slab, refilling it and moving the P-trap? Of coursee if it necessary, I will do what is best.
    marc
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,134
    Location:
    New England
    The drain needs to be low enough so that you end up with 1/4" per foot from the furthest wall. So, if it is say 4' away from the furthest wall, you need it to be 1" below the floor level there. Now, also, to look professional, your floor height should be even all the way around the shower. This means that you will have a 1" fall from the short wall distance to that drain, not good. Check out www.johnbridge.com and read their shower construction info in the "liberry" (sic); it will help answer your tiling questions. The guys here can help you get the drain connected.

    There are some neat alternatives to a "traditional" shower construction. Check out Kerdi from www.schluter.com. It solves problems you didn't know you had, and is a neat way to go.
  9. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Tub Replacement w/shower paan

    OK then Jim. I will do as you advise. As for the Kerdi shower, money is always an issue; I am a minister and do a lot of volunteer work for our elderly poor helping them with home repairs, so I live on very little. This renovation has to be affordable. That is one reason why I am doing it myself,besides the fact that we live in a small rural area that does not have any craftsmen/women.
    But, I will first dig down to find the old P-trap, then break out the slabonly enough to run 2 inch PVC pipe and new P-trap to the center of the pan.
    How can I determine at what height to set the Oatey drain so that it will be at the correct height once the pre-slope, membrane and final deck mud are in place?
    marc
    Last edited: Jun 12, 2006
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,134
    Location:
    New England
    The traditional shower construction has worked for a long time, so you should be fine if you follow the instructions. Suggest you ask your height question over on the www.johnbridge.com site. The info in their "liberry" covers it all, and you can ask tiling specific questions there as well. As a reference, the layers would be: deck mud for pre-slope, liner, final deck mud (constant thickness), thinset and tile. On the walls, a vapor barrier, then cement board (cbu). Tape the seams with the alkali resistant tape (do it as you tile) and thinset and tile. No screws or nails in the cbu through the liner. Run the cbu down over the liner before you put in the final slope so that top layer holds the bottom of the cbu in place. Make sure there is blocking behind the cbu near the bottom so it doesn't just flop around. Good luck.
  11. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Tub Replacement w/shower paan

    Hi Jim and thanks again. I have placed 2 x 12's between the wall studs for both blocking and attachment of the membrane. I plan to use a 6 mil.plastic vapor barrier under the Durock, then tape the seams as you advise. I also want to paint the seams with Red Guard to assure protection, ( I don't want to do this again.) My biggest challenges now is breaking through the slab and then getting the membrane to fit well enough not to interfere with the placement of the Durock. As we have a second bathroom, I intend to take my time and do the best that I can.
    marc
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,134
    Location:
    New England
    Suggested order of things:

    blocking
    drain centering
    preslope
    membrane
    vapor barrier
    cbu
    final slope
    tile (some people like to do the walls first, then the floor, but it doesn't matter. If you want the floor tile to go under the walls, you can do all of the walls except the bottom row, do the floor, then the last wall row)
    grout
    sealer
    shower
  13. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Tub Replacement w/shower pan

    Many thanks for all of your help Jim.
    marc
  14. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Shower Drain

    Hi Jim et.al. I made a mistake in measuring the drain after I removed the tub. It is actually a 1 1/2 inch that goes straight down into the sand and below the slab. I dug down about 6 inches, but could not find a p-trap. The former owner was a building contractor. Can I safely assume that the trap is don below the slab close to the septic tank where I cant reach it? Will I do any harm by putting in another for the tub to shower stall conversion?
    Thanks in advance,
    marc
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,134
    Location:
    New England
    Well, to pass code, you will need to keep digging and follow that pipe back. A shower requires a 2" drain, and you can't just increase the pipe diameter at the trap, you can go bigger, but not in that direction.

    Some contractors don't build things like they are supposed to be done...
  16. and you really really cannot add another P-trap in series with an existing one.
  17. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Tub Replacement w/shower pan

    Well, I did keep digging and found a 2 inch P-trap with a 1 1/2 inch straight pipe attached via an adapter. I dug out all of the sand around it so I would have room to work.I also drilled and made an access through the slab at the center of the shower stall. I then cut off the trap at the point where it connected to a 2 inch straight pipe. I solvent welded a 2 inch sanitary 90 degree ell and brought a straight section of pipe to the center of the shower slab. At that point I connected a 2 inch P-trap and then a vertical 2 inch sched. 40 pipe to 1/2 inch above the slab. The pipe was plumbedand then was plugged with a rag until I finish the blocking and framing. I packed the sand back in the whole up to the slab and compacted it firm with a 2x4.
    I feel better now that I found the P-trap and moved it's location to right below the 2 inch Oatey drain. Thanks again gentlemen. I have worked in emergency medicine for over 40 years, so if I can return the favor please e-mail me directly for any questions or advice.
    marc
  18. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Replacing tub w/ showerpan

    I have chiseled out the concrete slab to center the drain. That was quite a job.I am ready to remopve the tub P-trap and move the new drain to the center of the shower floor. My questions aare:
    1) At what height do I attach the new PVC drain and trap,(I will be using a PVC shower pan after I apply a dry mud bed over a Thinset bonding to the slab);
    2) How can I predetermine the height of the Oatey drain so that it is seated properly considering that I will be using a preslope deck mud, PVC liner, then anotherr deck mud base, then tile;
    3) Is there a minimum height /depth of the vertical pipe from the shower drain to the P-trap, ( is there a required distance of vertical drop);
    I know that for the horizontal pipe I must have 1/4 inch per foot of run to the main waste pipe. This is not as easy as it looks on This Old House!
    marc
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,134
    Location:
    New England
    There is a maximum depth of the trap (too much velocity), but there is no minimum depth of the trap. The thickness of the preslope under the drain isn't a big problem if it is on a concrete slab - but they like something like 3/4" or so. If you go over to www.johnbridge.com and check out the "Liberry", there's a detailed discussion on this topic.
  20. marc4790

    marc4790 New Member

    Messages:
    11
    Location:
    Keystone Heights, FL.
    Replacing tub w/ showerpan

    Thanks Jim. I will check out that posting in the "Liberry"
    Marc
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