I just bought a 1980's condo, and there is no p-trap under the kitchen sink. The drain is down into the slab. It's a 50/50 sink with a disposal on the left. Is a p-trap still needed with this vertical drain? Thank you.

  • 1
    You can buy a usb camera for cheap and send it down the pipe to see if there is a P trap in the slab or not. – Damon May 9 '15 at 22:49
  • Renting an inspection cam (or asking a plumber to do the same) sounds like the safest bet. You or your plumber might be able to "feel out" a trap with a snake, but that's probably not as reliable as the camera. – ThreePhaseEel Aug 7 '15 at 2:34
  • If it's a condo, maybe ask the neighbors if you can look under their sinks for clues. – DA01 Aug 7 '15 at 3:51

If there is already a trap underground, you won't need a trap under the sink - indeed if you added one, you will have major problems with draining with a double-trapped setup.

  • Yep. And there is my dilemma. i know of no way to tell if there is already one underground. But i did not think that was ever done. Are p-traps sometimes installed in the slab? – Joe G May 9 '15 at 10:51
  • 1
    Not usually, but I've seen that pretty much anything is possible! If it isn't trapped, I'd expect you'd soon notice the drain smell in the room. – John May 11 '15 at 7:48

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