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Why is this venting not permitted?

Discussion in 'Plumbing Codes' started by Michael.L, May 15, 2019.

  1. Michael.L

    Michael.L Sawhorse

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    Mop Sink Drain 2.png

    I was told that my hand sink drain cannot be used to vent the mop sink because this is not part of a bathroom group. What I don't understand is, why does this not comply with Section 911 of the IPC?

    IPC 911.3 Connection at different levels.
    Where the fixture drains connect at different levels, the vent shall connect as a vertical extension of the vertical drain. The vertical drain pipe connecting the two fixture drains shall be considered to be the vent for the lower fixture drain, and shall be sized in accordance with Table 911.3. The upper fixture shall not be a water closet.​

    Could someone please explain why this plumbing does not meet code?
     
  2. cda

    cda Sawhorse

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  3. jeffc

    jeffc Bronze Member

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    “Everyone does it this way.” That is just your standard vertical wet vent that has been used and legal for years. I wonder if the horizontal wet vent provisions are being inappropriately applied to this situation.
     
  4. Michael.L

    Michael.L Sawhorse

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    Only one floor in the building, so everything is on the same floor level. Pipe sizing is correct, as far I'm aware. I was told the issue is that the mop sink is venting through the wet discharge pipe of the hand sink. But it seems that should be acceptable according to IPC 911.3.

    I'm just trying to understand the code.
     
  5. Michael.L

    Michael.L Sawhorse

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    I think some confusion may come from IPC Section 912 on Wet Venting:

    912.1.1 Vertical wet vent permitted.
    Any combination of fixtures within two bathroom groups located on the same floor level is permitted to be vented by a vertical wet vent. The vertical wet vent shall be considered to be the vent for the fixtures and shall extend from the connection of the dry vent down to the lowest fixture drain connection. Each wet-vented fixture shall connect independently to the vertical wet vent. Water closet drains shall connect at the same elevation. Other fixture drains shall connect above or at the same elevation as the water closet fixture drains. The dry-vent connection to the vertical wet vent shall be an individual or common vent serving one or two fixtures.​

    Since this section addresses wet venting specifically for "within two bathroom groups" it may be that people are interpreting that (correctly or incorrectly) as excluding all wet vents for similar fixture configurations not contained within a bathroom group. But if wet venting is only permitted within bathroom groups, then how is that limitation reconciled with the Common Venting stipulated in IPC 911.3?
     
  6. Keystone

    Keystone Sawhorse

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    What Code section did the inspector cite.
     
    #6 Keystone, May 15, 2019
    Last edited: May 15, 2019
  7. cda

    cda Sawhorse

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    Did the person saying it is wrong,,,

    Cite the code section that they say is in violation ????
     
  8. conarb

    conarb Sawhorse

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    It may be because I'm in California, which is UPC and not IPC based, but as far as I recall wet-venting has always been illegal.
     
  9. cda

    cda Sawhorse

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    Is the definition the reason it is not allowed::::::


    BATHROOM GROUP. A group of fixtures consisting of a water closet, lavatory, bathtub or shower, including or excluding a bidet, an emergency floor drain or both. Such fixtures are located together on the same floor level.
     
  10. Michael.L

    Michael.L Sawhorse

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    This has not yet been built nor inspected. I'm planning the layout and want to ensure everything will "work" and be code compliant. I posted this configuration on a plumbing forum and was told it would not pass inspection; no codes were cited by the two plumbers who said it wouldn't pass.

    When I asked about IPC 911.3, one of the plumbers stated that he operates under UPC and that it might pass under IPC (which is the plumbing code adopted by my jurisdiction); he didn't know for sure. I'm hoping I may get a more authoritative answer on the code requirements here than on the plumbing forum.
     
  11. Michael.L

    Michael.L Sawhorse

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    My jurisdiction has adopted IPC, not UPC. That said, based on my reading of the 2018 UPC, wet venting is permitted. Furthermore, there is no mention of bathroom groups in the UPC section on vertical wet venting.

    UPC 908.0 Wet Venting
    908.1 Vertical Wet Venting.
    Wet venting is limited to vertical drainage piping receiving the discharge from the trap arm of one and two fixture unit fixtures that also serves as a vent not exceeding four fixtures. Wet-vented fixtures shall be within the same story; provided, further, that fixtures with a continuous vent discharging into a wet vent shall be within the same story as the wet-vented fixtures. No wet vent shall exceed 6 feet (1829 mm) in developed length.
     
  12. Michael.L

    Michael.L Sawhorse

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  13. cda

    cda Sawhorse

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    Maybe call the locals and either email your diagram or go by and ask the question
     
  14. Michael.L

    Michael.L Sawhorse

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    I had previously emailed the local Building Dept official to request a preliminary meeting to discuss some issues regarding the build-out. He replied that they are too small an office to meet in advance and that I should simply submit my TI building application.
     
  15. Michael.L

    Michael.L Sawhorse

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    Here is the diagram from the ICC's publication on venting:

    IPC Common Venting.png
    Again, there is no discussion in IPC Section 911 that states Common Venting is restricted only to bathroom groups.
     
  16. cda

    cda Sawhorse

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    Submit it

    Cite the code section on the plans, so it shows you researched it and cited sections to support your design

    Do not understand why the bo can’t give you fifteen minutes

    To me it saves him time down the line

    Or maybe he is to busy to even notice the vent set up, when you submit!!!!!!
     
    my250r11, Joe Engel and Michael.L like this.
  17. HForester

    HForester Member

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    The arrangement is compliant with the IPC (and IRC) "common vent" section. Although it is not termed a "wet vent" system it is a very simple wet vent for the lower fixture.

    I don't know about the UPC...it is getting too hard to decipher that language.
     
    Michael.L likes this.
  18. Michael.L

    Michael.L Sawhorse

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    From my reading of the IPC (and UPC), I'm not sure how one distinguishes a "simple wet vent" from a "wet vent system." There really needs to be greater clarity in the code. Particularly in the IPC & UPC sections on Wet Venting.
     
  19. HForester

    HForester Member

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    All I am saying that is that a common vent (connecting at two different levels) is like a simple vertical wet vent...the flow from upper fixture passes through the same pipe as the venting air for the lower fixture. In your arrangement, you call it a common vent as it meets all the rules for a common vent.
     
    Michael.L likes this.
  20. Mech

    Mech Sawhorse

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    At a quick glance, you might be able to call this a waste stack vent (Section 913 in the '18 IPC) provided the pipe sizing is correct.
     

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