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Thread: Wet Venting Shower Trap

  1. #1
    Geologist sjsmithjr's Avatar
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    Default Wet Venting Shower Trap

    Anyone care to comment on the way the shower trap is vented in the attached diagram. I think it's correct under the IPC but would like to know for sure.

    Thanks,
    Sam Smith
    Knoxville, TN
    Last edited by sjsmithjr; 03-08-2013 at 01:11 PM. Reason: No sense wasting perfectly good server space with an incorrect layout!

  2. #2
    Test, Don't Guess! cacher_chick's Avatar
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    No, that is not how a wet vent works. The lav waste is flowing past an unvented shower trap arm.
    Last edited by cacher_chick; 03-07-2013 at 09:56 AM.

  3. #3
    Geologist sjsmithjr's Avatar
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    Default 86 the Wet Vent

    Quote Originally Posted by cacher_chick View Post
    No, that is not how a wet vent works. The lav waste is flowing past an unvented shower trap arm.
    Thanks for the response. You're right (of course). The section I marked as the wet vent isn't. The wet vent starts where the lav arm intersects the vertical vent. At any rate it's wrong...

    I should have enough room to come off the trap arm with a wye and run the shower vent up the wall. The IPC does define vertical as 45 degrees or greater; right?

    Thanks again.
    -Sam
    Last edited by sjsmithjr; 03-07-2013 at 01:30 PM. Reason: Revised the text.

  4. #4
    Test, Don't Guess! cacher_chick's Avatar
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    45 degrees or greater anywhere below 42" above the floor. Your shower would be wet vented by the lavatory vent, but the distance between the trap and vent is too great for it to work properly or meet the code requirement.

  5. #5
    Geologist sjsmithjr's Avatar
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    Thought I give it another try after studying some more. This is supposed to be an example of a bathroom group vented by a dry vent upstream of wet vent. Governing code is the 2012 IPC; no local amendments. 6 DFU total on a 3-inch (5 DFU or more). Maximum trap to vent for the lavatory trap is 3 ft (2 ft as built). Maximum trap to vent for the shower is 5 ft (1 ft as built). Minimum trap weir to vent distance 2x diameter. Toilet distance to vent is unlimited. Am I getting this yet?

    Thanks!
    Sam

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    Last edited by sjsmithjr; 03-08-2013 at 01:59 PM.

  6. #6
    Test, Don't Guess! cacher_chick's Avatar
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    Flushing the water closet could siphon the shower trap.

  7. #7
    Moderator & Master Plumber hj's Avatar
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    The shower is "UNVENTED". Connect the shower to the sink riser and eliminate your problems. The "wyes" do NOT have to be rolled at all. You wrote, " This is supposed to be an example of a bathroom group vented by a dry vent upstream of wet vent". Is this part of a homework assignment?
    Last edited by hj; 03-09-2013 at 12:58 PM.
    Licensed residential and commercial plumber

  8. #8
    Geologist sjsmithjr's Avatar
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    Thank you both for taking the time to reply.

    Quote Originally Posted by hj View Post
    You wrote, " This is supposed to be an example of a bathroom group vented by a dry vent upstream of wet vent". Is this part of a homework assignment?
    I'm afraid it's been over 30 year since I had a homework assignment. I am trying to understand (for my own edification) the approach of venting an entire bathroom group (or two) using a "horizontal wet vent" under the IPC. What I've gathered from here and other forums is that even though it is allowed it's a bad idea. Seems the only reason to do it is to save a little bit of time, a few fittings, and a few feet of pipe. So while the building and electrical codes have become more stringent the plumbing code has become more lax. Around here at least it's the land of pex, sharkbites, and AAVs.

    For my own project I am venting the shower. I'm too far away from the lav riser but it's not a big deal to vent it individually.

    Thanks guys!
    Last edited by sjsmithjr; 03-10-2013 at 03:23 PM.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    PROPERLY done, there is no problem with using a wet vent for the toilet and shower. YOUR design is NOT properly done however. If your area uses the IPC, then it IS almost an "anything goes code".
    Licensed residential and commercial plumber

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