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Wanting to move a kitchen sink from a wet wall to an exterior wall, under a window. Isn't this the hope of every kitchen remodeler, to be looking out a window while standing in front of a sink?

My plumber's opinion is that my windows will not accommodate the 42" height above fixtures code requirement for venting (excerpted below).

I'm confused by this requirement, as the "kitchen sink under a window" pattern seems so common. I'm able to change the window's geometry but I'd prefer not to sacrifice the light the window provides. Are there workarounds I should know about?


18-29-905.5 Height above fixtures. A connection between a vent pipe and a vent stack or stack vent shall be made at least 6 inches (150 mm) above the flood level rim of the highest fixture served by the vent, and 42 inches (1067 mm) minimum above finished floor. Horizontal vent pipes forming branch vents, relief vents or loop vents shall be at least 6 inches (150 mm) above the flood level rim of the highest fixture served and 42 inches (1067 mm) above finished floor.

  • I am a bit perplexed as it is already on another wall in the same area , same height ? so how is the height on the wall with the window different than the current location ? How does that affect how your venting will be ? Can you no longer run a vent pipe because of the window in the way ? – Ken May 6 '17 at 19:53
  • The key words are "connection between a vent pipe and a vent stack" Your vent stack is not under your window because it runs up to the roof, so it is to the side of your window. your vent pipe would run from your sanitary tee over to the stack and connect with in the code measurements. – Alaska Man May 6 '17 at 23:27
  • Our kitchen sink has a large window above it. The vertical vent out the roof is in the wall about 48 inches from where the rough out drain enters the wall below the sink. The sink drains perfectly. – Jim Stewart May 6 '17 at 23:28
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Typical sink under window:

enter image description here

The venting issue is that you cannot connect to other vents or have a horizontal offset in the vent until it is 6" above the highest flood level rim and at minimum 42" above the floor (see the red portion in the above image).

To avoid a horizontal offset of the vent below the flood level rim, you simply arrange the drainage to come up beside the window, and pipe the sink's trap arm under the window over to the sink (see the green portion in the above image). The only limiting factor is the distance permitted on the arm (the fall cannot exceed the internal diameter of the pipe).

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