I'm getting ready to install a vertical 4" pipe to serve an upstairs bathroom and vent to the roof. At the bottom, in the basement, I want to install 2 45 degree bends to get from the wall out into the middle of the basement.

Are there any restrictions on using a 45 at the middle of the stack or how long it can be? I'd like to run 45 degrees for 16" then go to horizontal for a few feet before dropping the rest of the way to the basement floor.

  • Did you ever get this resolved? If so, please give a check-mark to the answer that helped you the most, or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer – FreeMan Aug 1 at 13:45
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    Doing this myself I haven't had it inspected yet, but best I can tell so long as the flat pieces are 1/4" per foot or more (1/8" for 4" I think), you're good. I also ended up running 3" pipe instead of 4" after talking to my father-in-law who's done more of this stuff. – RLZaleski Aug 1 at 17:07

2018 IPC states: (assuming you are under IPC code?)

SECTION 704 DRAINAGE PIPING INSTALLATION 704.1 Slope of horizontal drainage piping. Horizontal drainage piping shall be installed in uniform alignment at uniform slopes. The slope of a horizontal drainage pipe shall be not less than that indicated in Table 704.1 except that where the drainage piping is upstream of a grease interceptor, the slope of the piping shall be not less than 1/4 inch per foot (2-percent slope).

(<2.5": 1/4" per foot) (3-6" pipe: 1/8" per foot) (>=8": 1/16" per foot)

a. Slopes for piping draining to a grease interceptor shall comply with Section 704.1.

704.3 Connections to offsets and bases of stacks. Horizontal branches shall connect to the bases of stacks at a point located not less than 10 times the diameter of the drainage stack downstream from the stack. Horizontal branches shall connect to horizontal stack offsets at a point located not less than 10 times the diameter of the drainage stack downstream from the upper stack."

You can search the IPC for other details here: https://www.ci.independence.mo.us/userdocs/ComDev/2018%20INTL%20PLUMBING%20CODE.pdf

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