I'm remodeling my half bath (guest). New sink, toilet, fixtures, floor, etc.

Sink is mounted, but the existing waste line is exposed about 1 1/2" too much (previously this was hidden in the cabinet space). I need to shorten it to allow the 'P' fitting to line up to the sink drain drop. Because the previous fixtures and supply/waste lines were hidden in the cabinet work, the sink could line up. The new sink, wider, sits off-center from the waste line so a "bottle trap" doesn't work in this situation. I need to be able to offset the sink drain to 'P' fitting just slightly. However, the exposed wall line is such that the fitting will not compress properly.

I've tried unscrewing the waste line from what I presume is an elbow behind the wallboard (however, insulation prevents me from confirming this).

What are my options? Can I saw it off and refit it with a compression reducer (behind the what appears to be an existing reducer)?

Much thanks,
Tim

This message has been edited. Last edited by: javafueled,

As it turns out, the waste line to the wall is 1 1/2 copper. It makes a left 90˚ bend horizontally behind the wall board about 3" then straight down to the crawl.

This prevents me from "twisting" it off at an elbow as originally hypothesized. But being copper, it changes the mechanics significantly.

I should be able to cut it flush to the wall board and reduce it to a compression fitting much easier now.

More later.

This message has been edited. Last edited by: javafueled,

you sure? that looks like a hose bibb on the end of a 3/4 inch copper line to me.

if so, it's not legal drain line.

wallboard is easy to patch. I'd cut a rectangle out and see what's really back there. this looks way fishy to me.

It is 1 1/2 copper exiting the wall. Confirmed.

I polished it up, the cut it flush to the wall. I knock a bit out around the waste line to confirm its install and route. Short story on the existing waste line: I wasn't going to be able to cut it in the crawl and put a new one in without extensive wallwork to pull the mounting blocks from studs that could be seen from the hole.

After I cut it flush to the wall, I shorten it further with a Dremel tool and metal cutting wheel inserted into the waste line. This took another 1/4" or 3/8".

I was then able to obtain both 1 1/2" copper, a new 1 1/4" adapter and connecting sleeve. Consulting with the plumbing expert at my Friendly Local Supply House, he suggested PC-7 epoxy on a waste line versus sweating the copper.

overall this allowed me to shorten the exiting waste line exiting the wall a full 1/2" to 5/8". Enough that allowed me to set the 'P' pipe and compression nut without leaks!

The house is over 40 years old and inspection under the house shows use of copper to all supply lines and most waste lines (gray water at least).