Residential DWV layout suggestions

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Nwhits

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Hello,

I am new to this forum and pretty new to plumbing besides fixing something that already exists. I am adding a bathroom to the second floor of my house and I think after reading through a bunch of different threads on this forum that I have a layout that will function correctly but was hoping for some feedback on if it is actually correct or any changes you may make. I'm from Pennsylvania. There is only one bathroom in the house and it is directly below this on on the first floor. My floor joists are 2x10 and exterior walls are 2x4. I am planning on running two separate waste stacks to avoid cutting across the floor joists. The 3" stack will go down through a closet corner on the first floor and be boxed in and the 2" stack I can run down through the inside of one of the side walls.

Thank you!

Nick
 

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wwhitney

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I am reading all of your diagrams to be planar, i.e. up and down the page is always vertical. Then a few comments based on the IPC, which PA uses:

With wet venting, in each of your diagrams, the lav dry vent is the only vent you need. I.e. you can change the san-tee in the lower right of each diagram to an elbow and omit the dry vent coming off the top.

On the shower wet vent, the shower trap needs to be at the same elevation as the wye or combo where the shower drain joins the lav drain that is wet venting it. That is, the fitting where the two drains join is the vent for the shower, and the shower trap arm, between the trap outlet and that fitting, is limited in total fall to one pipe diameter. So you can't have a 90 with a vertical outlet in between the shower trap and the lav drain. In other words, the wye or combo where the two drains meet has to be horizontal (both inlets horizontal).

On the WC, there is some debate about whether the wye or combo where the WC drain joins the lav drain has to be horizontal. If it is not difficult to make it horizontal, then that's the simplest/best choice. If it would be difficult, then some more research is required to determine if your project is subject to any adopted language (such as the IRC plumbing sections) that would require it to be horizontal, or if you would be allowed to have the WC come into the fitting vertically.

Cheers, Wayne
 
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Nwhits

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Wayne,

Thank you for the clear explanations of what is wrong and how to correct it! I will update both layouts to have the shower and WC wyes horizontal. For the WC I will either move my WC over pending on the proximity to the window or move my drain to the opposite side floor joist to let the WC where it is and have enough space to tie in horizontally. I can 45 over in the closet once I get to the vertical stack to place it in the corner if I have to move the drain over .

Thanks again

Nick
 
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