I live in San Francisco, and my kitchen sink drain goes through my wall towards outside of the wall of the house into a light well. The steel pipes have rusted out so I want to replace them with ABS. Does any one know if this is legal or to code in SF? I have read that it is recommended to use a heavier duty pipe for more resistance to UV rays so maybe that would be “more” to code. Please advise!

  • can you fix (reline) the pipe instead of replacing it? saves a lot of time and materials... – dandavis Jan 7 '18 at 21:32
  • 1
    Call the local building inspection office. In various places I have seen plumbing drains on the outside of exterior walls. I believe this is a common practice when adding drains to older existing structures. UV protection can be accomplished by painting. But in your situation there might not be enough justification for exterior routing. Get an opinion from code enforcement. – Jim Stewart Jan 7 '18 at 21:54

I spoken with the San Francisco Building Code inspector and they said ABS exposed pipes are allowed as long as it is coated with UV protected paint since it’s located outdoors. Also ABS used for DWV applications are only allowed for buildings up to 2-stories private and commercial. For mixed material couplers, I would need to find a coupler made specifically for steel to plastic. Thanks @jim for telling me just to call the inspector.


It will look like hell but it will work.

  • Well, wouldn't that depend on climate? I wouldn't leave a sanitary pipe exposed out here, that's for sure! – ThreePhaseEel Jan 8 '18 at 3:17
  • The macrobiotic decomposition usually creates enough heat on its own to preclude drain pipes from freezing, at least in moderate climates. – Paul Logan Jan 9 '18 at 6:38
  • 1
    A Victorian with pipes and sewer stacks running vertically and diagonally along the building exterior, is still 10 times more appealing than the featureless, repetitive "little boxes full of ticky-tacky" that passes for housing in most places. – Harper - Reinstate Monica Jan 10 '18 at 0:38

For your climate PVC or ABS will work just fine since I’d doesn’t freeze however at least as of about 20 years ago San Francisco required all DWV pipe to be cast iron. San Francisco is a very liberal city with strong unions that lobbied for cast iron since it requires some skill to work with and beyond what most homeowners are willing to deal with giving union labor more work. This may have changed in the last 20 years though.

  • San Francisco allows ABS and PVC piping as long as it is used for DWV and it’s for a building 2-stories and below. This was the amended code from 2016 according to my call with the inspector – josephnvu Jan 9 '18 at 21:43
  • 1
    It's not just that. 3 storeys of pipe and water are heavy. – Harper - Reinstate Monica Jan 10 '18 at 0:35

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.