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Thread: Code requirement for custom shower drain?

  1. #1

    Default Code requirement for custom shower drain?

    Hello all, i'm a tile contractor looking at a custom walk in shower, the size of the shower pan is approx. 8.5 ft wide by 3.5 deep, with a showerhead on each side of the short walls

    local plumber tells me you need (2) 2" pvc drains for this setup, HOWEVER because this is a handicapped accessible shower the customer has already lowered the subfloor under the shower area so that the finished mortar bed height is equal to the rest of the floor.....no curb, and wheelchair rolls right in

    the lowered floor means some sistered joists, and this takes up the needed room for 2 drains.....sooo the plumber says we need (1) 3" drain instead

    1) is this correct, i live in the st. louis mo area if that makes any difference
    2) my real problem is that as the tile contractor i want to use a shower waterproofing system made by Schluter Systems called "KERDI" and they make their own drain to fit their waterproofing membrane, and it only comes in 1 size of course, the standard 2 inch....i don't know if there is a way to modify a standard 3" drain but maybe some of y'all might know about that??

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Kerdi is good stuff, but like any typical shower drain, it is designed for 2". I'm not a pro, but I don't see any good reason why you'd need two drains with only two showerheads...people get buy with 4-5 or more with only one. I loaned my TDNA handbook to someone so I can't see if they require two because of the size of the room, not the quantity of the heads. Have you checked with the inspector? The plumber might be right on, or he could be blowing smoke.

    Schluter talked about maybe making a trench drain, which might work for you. You might want to ask (I don't remember it in the catalog, but sometimes they have some things that aren't), but absolutely no guarantees.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    This raises a very interesting question.... I believe the code for a 2" shower drain was written with the assumption that everyone had 1 showerhead! I can see that a "thinking" inspector might add up ALL the available heads in a shower and base a drain requirements on perceived maximum input?

  4. #4
    Homeowner geniescience's Avatar
    Join Date
    Nov 2005
    humid summers hot, humid winters cold


    fight code with code. you are going to have to know more about code than the plumber is expecting you to know, to get him to back off.

    i think your plumber is thinking the floor surface area or the TWO showerheads now makes it bigger than ONE shower, so he concludes it needs a bigger drain.

    he is wrong.


  5. #5
    Plumber Cass's Avatar
    Join Date
    Nov 2005


    Ask him to show you in his code book the requirement for the 3" drain.

    If he doesn't, go with the 2" drain and be done with it.

  6. #6


    contacted the local county inspector and he said the plumber was "dead wrong"......nuff said

    1 drain, 2" pipe thats all ya need ....i'm relieved

  7. #7


    Are there going to be any body spays as well. He could also be recommending two drains since there is no curb the two heads could put out more flow than the one drain could keep up with.

  8. #8
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Jul 2009
    North Vancouver, BC
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 05:43 AM.

    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.


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