Code: California Building Code

Context: Connecting a Kitchen Sink + Dish drain to a Laundry sink and Vent. I would like to use a double san tee to connect 2" drain, 1.5" vent, and 1.5" laundry sink. I have little room and would prefer to use a double san tee over a double fixture fitting. Because of space constrain, the washing machine P trap has to be above the kitchen + dish drain. Note the existing setting below, a gas line is running right above the san tee. The vent is in the wall, the san tee is outside the wall. The san tee would be replaced with a double san tee.


  • Can I use a double san tee rather than a double fixture fitting? for horizontal to vertical flow.
  • Can I use a long turn tee wye to connect the washing machine drain?
  • S traps are not recommended, can I add a short horizontal 2" between the P trap and the Long turn tee wye for the washing machine?

Existing san tee to be replaced with double

Double San Tee or Double Fixture Fitting

Full setup for context

enter image description here

  • Your washing trap is an S trap as rough assembled. Commented Dec 5, 2022 at 1:06
  • what is the 2nd long turn y that feeds into the lower existing 2" line? Commented Dec 5, 2022 at 1:12
  • Thanks Fresh Codemonger. Yes, for the S trap, this is why I asked the following question: S traps are not recommended, can I add a short horizontal 2" between the P trap and the Long turn tee wye for the washing machine to make is a P trap?
    – Max
    Commented Dec 5, 2022 at 1:21
  • The 2nd long turn tee wye is fitting into the existing 2 in drain. See diagram at end of post on the garage side. Thanks
    – Max
    Commented Dec 5, 2022 at 1:22

2 Answers 2


You'd need to drain the p-trap into the vertical pipe that is the vent. The minimum trap arm length is 2 pipe diameter from the weir to the vent.



The other thing that could work for you is to put a vertical piece onto your long turn Y and add an aav above the flood line of your sink. Without the horizontal connection from the p-trap to the vent their is no vent for this trap. The air from the vent must reach the surface of the trap water. Your p-trap when in use will prevent air from reaching it.

You want the double fixture tee to allowing snaking to work properly. If you have the double sanitary and you snake the p-trap you'll go up the other p-trap instead of down the drain.


  • Thank you Fresh Codemonger - If I connect directly the P trap to the vent with a horizontal pipe, does the vertical drain stacking (bottom of Vent) of the washing machine on top of the double fixture tee create a problem? Is it code? See uploaded image to post.
    – Max
    Commented Dec 5, 2022 at 15:05
  • There isn't an issue code-wise with stacking the tees but from your picture, I don't think you have enough vertical room without opening up the wall to move the vent up.
    – pdd
    Commented May 28 at 22:54

You could simplify the arrangement by using a wet vent for the clothes washer with the kitchen sink and if the laundry sink distance is less than 6' the existing vent would serve it. The fixture drain for the clothes washer would have to be installed on the same horizontal plane as the wet vent (pipes would be side by side). After the p-trap, you can offset back to the wall with two 45° elbows.

And to answer your question, yes, you would use a double sanitary tee for this connection.

enter image description here

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