I'm in the process of adding an outdoor toilet and sink to the rear of my house and would like to connect the drain to the main sewer line at the back of the house.

Below is a photo of the existing setup to which I would like to connect the additional drain.

Where would you recommend making the connection? My main concern is backflow into the drain that I'm going to add.

enter image description here

  • 1
    What's coming in via the air gap setup?
    – isherwood
    Jan 10, 2020 at 18:32
  • 3
    This doesn't look like a main connection but a smaller line for the air conditioner drain connection.
    – JACK
    Jan 10, 2020 at 18:34
  • You know the whole toilet has to be higher than the point you tie into the sewer, right? So you'll have to dig into the ground to tie into t a sewer or the toilet will have to be elevated.
    – JPhi1618
    Jan 10, 2020 at 19:20
  • That's a combination wye which is wrong for a p-trap. Switch it to a sanitary tee while you are working on this. That is also a 2" line you can't add a toilet to a 2" line. I'd guess the air gapped thing is an output of a sump well. Jan 10, 2020 at 19:39
  • 1
    Er, no. No it doesn't. Even if you have an ejector pump which uses a 2" output line, there's no way you have an air gap in your poop pipe, nor would it have a trap like that. Or do I misunderstand your explanation?
    – isherwood
    Jan 10, 2020 at 20:21


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