I'm looking to add a powder room and laundry to the ground floor of our home. Most of the plumbing runs through the central wall on our side split and the W/C & lav will be on this wall too, making the draining/venting a bit simpler. However the laundry will not be on this wall so I'm hoping to use a cheater vent here so I don't need to drill half the joists in this room or open upper-floor walls to get a vent out the roof.

I've attached some diagrams of my plans and was hoping someone could give me some feedback / review things in general. Additionally, I have a couple more specific questions:

  1. Is it better to connect the powder room and laundry both directly to the stack or am I okay joining them. I'm trying to avoid cutting too much of the copper out.

  2. Is it possible to install back-to-back sinks that share a wall like the laundry/garage sinks in my diagram? If so what kind of fitting would work?

*NOTE: Stuff in blue is being added enter image description here

enter image description here

enter image description here

1 Answer 1


All and all it looks good!

Regarding the Powder Room:

It is totally fine to join the powder room and laundry room on the same branch (as in your last picture). In addition, if the height is limited, instead of using a 3x2 sanitary tee on the vertical pipe to the toilet, you can use a 3x2 wye on the horizontal pipe before the toilet 90° to connect the sink and still vent the toilet.

Back to Back Sinks:

Yes, you can install sinks back to back. The fitting used here is a double sanitary tee or sometimes referred to as a sanitary cross.

Additional Comments

Note that some locations require that there is a fire-rated separation between the garage and the rest of the house. You can still penetrate the wall but you may be required to provide an approved fire stopping around the penetration. What you use will depend on how the wall is constructed and the drainage materials used. The same would apply to the water pipe penetrations.

Where I live we cannot use 90° elbows when transitioning from vertical to horizontal. We are required to use two 45° elbows. It's a bit silly, as we can use a hub x hub 45° and a fitting x hub 45° together and get close to the same radius as a short sweep 90°, but code is code. I know that many other jurisdictions/codes allow the use of long sweep 90° elbows for vertical to horizontal transitions.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.