4

This is semi-related to another question I posted but more of a fundamental/elementary question about plumbing in general.

When one has a tight space, how does one make a run of pipe slope when only 45, 60, and 90 degree fittings are available?

For instance, I have this transition from a 3x3" Combo Tee-Wye that needs to run to a toilet flange. I have about 8 inches between joists to make this fit, so running perpendicular 90s under the toilet flange won't work.

Below I'm showing my goal (orange pipe sloped at 2 deg) and all the blue piping is plumb or otherwise following an X or Y axis. If I were to try and mate the orange and blue, they'd bind and not mate.

Also, I plan on using a 45 deg angle flange, but didn't have a 3D model for that. Either way, we're trying to transition from 90 degrees to roughly 88 in order to make sure that poop is flowing where it needs to.

enter image description here enter image description here enter image description here

Jeremy P. Beasley
  • 797
  • 4
  • 18

1 Answers1

6

Ah! Ok, so it's a common misconception that when a DWV drain pipe is labeled 90 degrees, it makes a true 90 degree angle. However, the drain slope is built into the fitting. The actual angle is defined by ASTM and is 91.2 degrees. So my mockup in blue above actually works fine.

Read more about built in slope here. This applies to many fittings but not all. https://www.hammerpedia.com/pipe-slope-how-to-slope-a-trap-arm/

ThreePhaseEel
  • 87,685
  • 36
  • 144
  • 243
Jeremy P. Beasley
  • 797
  • 4
  • 18