Moving P-Trap and Connecting PVC to Pipe?

[MickeyVA]

Hi. We are in the midst of a very small powder room renovation, and we are struggling a bit with the p-trap plumbing for the new wall-mounted sink. There was a wall-mounted sink previously, and the p-trap went low and made a left 90 degree turn into the vent/drain pipe. Since we are trying to clean up some of the piping and minimize it, we'd like to move the p-trap up higher on the drainpipe. Ideally, we'd like to have the p-trap turned and just go straight into the drainpipe instead of having an extra 90-degree turn. However, we have PVC going to a galvanized pipe, which I believe is threaded. The galvanized pipe is a vent for other things, but it does not seem to be a drain for any fixtures above the powder room - only a vent. Is it possible to take out the existing santee, cut the galvanized pipe, and then move the santee higher up and still connect the PVC to the cut galvanized pipe without threads? Can we use a proflex neoprene shielded coupling in the wall or something else? Any thoughts would be greatly appreciated! Also, my notes on the drawing for where we want to move the p-trap is not exact. Hopefully it gives an idea though!

 

[Terry]

You can cut the galvanized pipe and connect with a shielded coupling.
No needs for using the threads on a vent or waste line.

 

[Sponsor]

 

[Reach4]

However, we have PVC going to a galvanized pipe, which I believe is threaded. The galvanized pipe is a vent for other things, but it does not seem to be a drain for any fixtures above the powder room - only a vent. Is it possible to take out the existing santee, cut the galvanized pipe, and then move the santee higher up and still connect the PVC to the cut galvanized pipe without threads? Can we use a proflex neoprene shielded coupling in the wall or something else?

You can and should use the shielded couplings you suggest.

You are going to cut the galvanized, but you should make sure the pipe is supported before cutting.

You won't have good enough access to cut with a cutoff wheel. You will use a reciprocating saw, and try to avoid poking through the other side. Not poking through the other side is probably going to be impossible. Maybe you could use a cable saw. Usually those are only used for plastic pipe. There may be one that can cut galvanized, but I don't find one. I have never used a cable saw.
https://www.homedepot.com/s/cable%20saw?NCNI-5