Adding vent to kitchen sink

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Uncle Lar, Jun 29, 2005.

  1. Uncle Lar

    Uncle Lar New Member

    Jun 29, 2005
    Naperville, IL
    I am in the process of remodelling the kitchen in our summer lake cottage. I would like to bring the DWV for the kitchen sink up to code. The sink cabinet is to be installed on an outside wall below a 32" wide window centered over the sink. The old installation did not have a proper vent. The sink drains into its own dry well. The drain pipe is 2" galvanized reduced to 1.5" as it comes up through the floor about 12" from the wall and not centered on the sink location. (It's more in line with the drain on the right bowl of a double bowl sink.) I need to figure out what PVC parts I need and how to route the vent from the point at which the sink trap meets the drain pipe back into the outside wall, around the window framing and up into the attic.


    1. Is a vent of 1.25" PVC adequate, or do I need to use 1.5", the same as the drain pipe?

    2. If I need to use 1.5" pipe, what are the rules for boring through the cripple, jack and support studs under and along side the window?

    3. The critical distance from the sink trap to the drain pipe is only a couple of inches. Do the critical distance calculations come into play for the horizontal runs of the vent pipe back to and inside the wall?

    4. Where the vent meets the drain, does the vent pipe need to run back to the wall at a 45 degree vertical angle to prevent clogging from backed up waste water?

    5. Does the horizontal run of the vent to reach the the right side of the window need to be 6" above the flood level of the sink?

    6. What cleanout access do I need other than dropping the trap from the sink?

    Thanks for your help.

    Uncle Lar
    Last edited by a moderator: Jun 29, 2005
  2. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    The vent can go horizontal below the window, but will need what is considered waste fittings below the flood level.

    Going up from the sink, you could start with a med 90, and then when it turns up toward the roof, a long turn 90.

    You would add a 2" cleanout below the trap arm.

    A kitchen vent could be 1.25" but where would you find the right waste fittings for it?

    Everyone else uses 1.5" pipe. You can drill a 2.125" hole through the studs.
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  4. srdenny

    srdenny Plumbing Contractor

    Sep 11, 2004
    Plumbing Contractor
    SF Peninsula
    Everyone else uses 1.5" pipe. You can drill a 2.125" hole through the studs.[/QUOTE]

    Or you can use DWV copper and drill a 1.75" hole.
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