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Thread: P-Trap into floor drain? Or is that an S-Trap? (and not good)

  1. #1
    DIY Junior Member bretm1's Avatar
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    Default P-Trap into floor drain? Or is that an S-Trap? (and not good)

    Hello

    First post. Did some searching, but couldn't get clear. I am "fairly" skilled but am not a pro. Just a do it yourself type. I am in Mass, have replaced a vanity in bathroom on second floor in a house built in early 1900's. The existing vanity has been there for 10-15 years. Of course the new vanity doesn't line up with the drain but I can deal with that, but the drain is on the floor (vertical?) going staight down to somewhere. I can not tell if there is P Trap under the floor unless I rip the floor up. Do I need to do this?

    Am I "stuck" with having to use an S-Trap (which may not be to code) because the drain is in the floor? I'm assuming that because I have to take the "P"Trap and then come off with a ninety degree elbow to the floor that this essentially creates an S-Trap. The trap I removed was like this. Not sure if I go straight off the P and then down if that will make a difference, but there is no room to do this. We have been in the house five years and never smelled anything, but I know that may not mean much.

    I'm kind of confused. Sorry If I didn't search well enough. Input appreciated

    Thanks

  2. #2
    In the Trades SacCity's Avatar
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    Sounds like an S trap.
    However there is always the Grandfather clause,
    As long as it was legal when done you don't have to change it,
    But if you touch the plumbing in the walls you will have to bring it up to current code...

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    Some inspectors would treat changing the sink and vanity as new, and require all of the stuff to meet current codes. There is a limit on how long the drop from the sink can be before it hits the trap. Having a trap below the floor is likely to be longer than allowed unless the sink is very deep and the vanity is on the low side. Plus, in MA, it is generally illegal for a homeowner to do plumbing without a license, even in their own home.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    Moderator & Master Plumber hj's Avatar
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    "New" or "old", you still have an "S" trap. The only way NOT to have an "S" trap is to install an AAV at the point where it turns down.

  5. #5
    In the Trades SacCity's Avatar
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    HJ - Thanks for providing a solution.
    I had not thuoght of an Air Admittance Valve (AAV)

    http://www.toolbase.org/TechInventor...ntDetailID=851

    Thanks again.
    Michael

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