I currently have a kitchen sink on the first floor which leads to a vertical pipe (illustrated in black). I would like to connect a bathroom sink to the same vertical pipe (illustrated in orange). Can I do this using a 90 degree tee or does both pipes have to be connected separately to the vertical pipe? enter image description here

  • Is there a vent pipe anywhere? Generally you would connect two separate sinks to the same vertical pipe using a double fixture sanitary tee. Commented Sep 18, 2021 at 18:15

2 Answers 2


Use two 90 degree sanitary tees for this, one for each sink. You'll never be able to unclog the drain with a tee as you've got it shown.

enter image description here

If space is limited, you can use a double fixture fitting like the one below.

enter image description here

  • I wont be able to drain unclog the vertical pipe you mean? If I would install a inspection in the vertical pipe? I also considered two tees, but it is up in a ceiling and space is very limited.
    – MLEN
    Commented Sep 18, 2021 at 17:59
  • 1
    @MLEN Yes, you won't be able to unclog the vertical stack from either sink.
    – JACK
    Commented Sep 18, 2021 at 18:46

For reduced clearance, use a "double wye" or a "double fixture fitting" and cap off the vertical (the opening at the top).

You need the sweep for the clean-out and to prevent water crossing over or inhibiting flow when both sinks in use.

enter image description here

Image: https://www.pmmag.com/articles/102042-riding-the-plumbing-roller-coaster-direction-changes-in-a-system-give-water-a-wild-ride

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