After calling about 8 companies and only having two come out who no longer answer, I'm going to give this one a shot before throwing in the towel. This is via permit and I'd like to be super sure before the inspection. This is in Michigan and I believe we follow a modified version of the 2015 IBC, if that helps at all.

I have a small old room that had been modifed to be a laundry room and we'd like to make it a bathroom. It is on the second floor of a house, with a 3" waste/vent in one of the walls. The proposed layout is shown here:

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The red circle is the waste stack. The following image shows sink (bottom left), shower (bottom right) and toilet (top) drain locations and how I think they should connect to the drain. The joists are 2x10, but actual is a hair less than 9 and have been sistered. The top plate runs under the toilet and the toilet drain would enter an interior kitchen soffit before turning to the stack.

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The toilet is on 3", shower on 2", sink on 1.5".

I have the following questions if you could help:

  1. Does the run distance for the sink and/or shower require venting? I think it's ~4 or 5 linear feet in sink drain option 2 to the shower drain. Shower drain is ~6 or 7 feet to the main stack.
  2. Addendum to above: There is a much closer 3" vent stack a few feet behind the wall - are the vent and drain pipes required to be the same?
  3. I can't figure out a location to put a cleanout - is it required and where would be a good spot?
  4. I think reaming out the existing/newish sanitary tee on the 3" stack (see below) and fitting a 3" street tee makes sense. Right below it, you can see another sanitary tee from a toilet in the next room. Issues with that?
  5. Initially, I was told by the plumber they don't usually see pressure tests with this kind of stuff when inspected, but in the case of it being necessary, how could I possibly set that up?

Thank you for your time. Some views of the stack from in the soffit:

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  • Let me make sure I understand first. You have a drain from the pre-existing washing machine since this was a laundry area but you need to add drain pipes (and water supply pipes?) for a toilet and a lavatory (sink)? Jul 14, 2019 at 18:08
  • The toilet, lav and shower all need to tie into the vent stack correctly or water will be siphoned from the pipes and you will smell sewer gases in the house. Your drain pipes need to run and connect from smaller to larger size pipes to prevent them from backing up. I suggest you post your questions on Terry Love Plumbing's blog so real plumbers and engineers can assist you. Hope this helps! Jul 14, 2019 at 18:14
  • Thanks, I was just looking at that forum. That's more or less what I was trying to figure out, is the run distance too great for the pipe diameter, etc.
    – James F
    Jul 14, 2019 at 19:10

1 Answer 1


What is the total number of fixture units that you have on your 3" line? The clean out is not necessary, provided you can access it from the roof or another clean out is further up line. additional venting is not necessary. From viewing your photos, I would call in a professional plumber and have the repair done correctly and have someone that can be called back if some thing goes wrong. One last bit of advice, contact your local authority and have them look at your sketches of what you are doing, this could be the best way to get the information that you are looking for.

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