I have a couple of connections that seem like they could work but due to lack of the inside bevel I'm questioning whether or not this will be a good idea.

In both cases the threads match and the rubber gasket/washer snugs up nicely creating what feels like a good fit. However, the inside of the straight pipe does not have any inside bevel, whereas normally that gasket joins with pipe that has a angle inside so that it really connects.

Are either of these things acceptable?

Polypropylene to copper drain with male thread:

Polypropylene to copper drain with male thread

Polypropylene to Oatey Sure-Vent:

Polypropylene to Oatey Sure-Vent

  • Haven't seen these fittings, but I assume you checked that the bevel is not on the inside of the compression nut? Your vent photo doesn't show a clear bevel.
    – K H
    Commented Apr 24, 2021 at 14:52
  • 1
    I would guess the intended compression could deform the seal in an unfavorable way.
    – K H
    Commented Apr 24, 2021 at 15:00
  • Your second comment is more my concern. Neither the vent nor the copper have any bevel. There is actually already a sink in this house that has this exact connection and appears to be doing ok. Based on that I assume it can work, but I'm still looking for some kind of verification that this isn't a terrible idea. The good news is, both of these connections will be under a utility sink and therefore visible in case of issues. Commented Apr 24, 2021 at 15:34

1 Answer 1


Polypropylene to copper drain with male thread

You should use a rubber 1 1/2" slip-joint gasket for this connection.

enter image description here

Polypropylene to Oatey Sure-Vent

What you have should work fine, as long as the tapered edge of the slip-joint washer fits into the ID of the fitting (as opposed to butting up against it...)

  • Can you post an image or link to the 1 1/2" slip-joint gasket you mentioned? I thought that's exactly what I have on the end of that plastic pipe..? Commented Apr 24, 2021 at 15:36
  • And yes, in neither case does the washer butt up against the adjoining pipe. Commented Apr 24, 2021 at 15:40
  • I posted an image of a square-cut rubber slip-joint washer. The plastic one you have now may work if it fits into the ID of the male copper fitting (which will allow the squeeze needed when you tighten it up, otherwise use rubber there. NOTE - there is a common misconception that hand-tightening slip-joint drain fittings is sufficient; this is incorrect, they need to be cinched up with a wrench. Commented Apr 24, 2021 at 16:33

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