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I live in an IPC state.

This is a picture of our interior walls of our laundry room. We are about to get new laundry machines and we want to add a sink on the left of the room against the wall (sorry for the extra stuff in view, the room behind the laundry room is a bathroom).

The center of the sink will essentially be in line with the 1.5” vent on the left. I don’t think I can simply drain into that section of pipe because that creates a wet vent which I don’t think is allowed for washers… right?

Assuming that’s correct, the other option I could see is draining the sink directly into the standpipe with no p trap underneath the sink so I don’t have a double trap situation. I do believe this is to code although not ideal.Is this my best bet?

Or should I replace the sanitary tee with a double sanitary tee and drain my sink to the left of the existing vertical stack? I think this works but isn’t as easy.

Or is there a better way?

Sorry if my terms aren’t 100% right - amateur here (obviously). Let me know what I can clarify. Thanks!

1 Answer 1


Under IPC (anyway - not all codes are the same, but most are similar) a 1.5" vertical wet vent is only good for one fixture unit, but a 2" vertical wet vent is good for 4 fixture units, (Table 912.3) and since a residential washer is 2 fixture units, changing the pipe to 2" up to the point that your new tray attaches would pass code venting requirements unless it's also venting other things.

The dry vent at 1.5" is good for 8-10 fixture units (table 906.1)

  • Thanks! Looks like I'll have to change out the existing sanitary tee, then, but otherwise this should work for me.
    – Kfly12
    Apr 24, 2023 at 16:17
  • If you don't cut it too close, you should be able to use it again (higher, for the sink) with the purchase of 3 couplings - unless 3 couplings costs more than a new one.
    – Ecnerwal
    Apr 24, 2023 at 16:27

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