My basement drain started backing up and after giving it a good look things look odd and I'm wondering how exactly things are set up. Below is a link to a diagram I tried to make and I'll try to explain it. The only thing that causes the drain to backup is running 1 sink. After removing the drain cover and cleaning it out a bit things weren't as I expected. There is the horizontal pipe coming from the sink which water comes from. But then there is an elbow joint with no openings which is the first thing you see, then in the back corner (which took a bit to find) there is a vertical pipe coming straight up which seems to be what should be draining the basin but is clogged. This isn't a normal setup, right? Would that vertical pipe have a p trap? When removing the drain cover and another rubber seal the smell coming from the drain is awful.

drain diagram


The house was built in the 1890s and has had I think 2 major additions.

  • I'd imagine a U below & between the "vertical pipe" and the "elbow no openings" making a trap just off the diagram, just looking at the diagram. You'd want a pretty flexible snake to snake that out, if so. Where is this "other rubber seal" you mention? Is the drain cover closed/solid, or also serving as a floor drain? – Ecnerwal Sep 11 at 3:15
  • first thing to do is "roto-root" the outflow pipe to unclog it. However, I doubt that the open pipe from the sink is anywhere near code, so at some point you may want to rebuild the system. – Carl Witthoft Sep 11 at 18:03

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