I had occasion to (try to) take off the P trap on my bathroom sink. The nut leading up to the sink drainpipe came loose fine. While I was struggling with the nut leading to the wall pipe, the pipe to the wall just came out. It popped out as if nothing was holding it in, and it’s not threaded or anything. There was a small amount of something dried and light brown around the end of the pipe, as if that was supposed to have held it in place, or at least sealed it from leaks.
So how do I put that pipe back in the wall, and what do I use to seal up this connection so it doesn’t leak waste water all over the cabinet floor? The only thing I could find at Home Depot that seemed close was pipe thread sealant, which I haven’t tried yet, but I thought it might be thick and gooey enough to do the job. Is that the same as pipe dope? I looked for that and couldn’t find any. Years of This Old House wasted.
Should I loosen that other connection nut so next time I can take off the P trap without the pipe coming out of the wall?
Is this a normal plumbing connection in modern bathrooms? It seems pretty insecure to me.
Can you see the opening that the “wall pipe” came out of?
My 60+ year-old house has something similar, and if I’m understanding correctly, there’s no rigid, threaded stub-out that comes into the under-sink area. The drain line that goes from the “P” trap to a “T” connection in the main(or semi-main) drain in the wall is just inserted and sealed with something. What that original something was I don’t know, but silicon sealant worked fine for me. I coated about two inches of the pipe with sealant, inserted it into the opening, and added additional sealant to the joint line just in case.
The exception was one sink where I couldn’t get a tight fit due(I suppose) to corrosion. But there was enough of a nipple that I was able to fit a rubber boot over it and tighten with simple hose clamps. But that was also the only sink where I had enough room to work in and get tools that far back. If one of the other sinks had a fitting problem like that, I would have had to figure out something else.
I always have a good supply of spit and baling wire.
The dry, light brown stuff is undoubtedlyplumber’s putty. There is no pressure on the drain line, so - excepting pipe blockage beyond the connection - no reason for the water to ever back up and leak into the cabinet. Plumber’s putty would fill the bill 99% of the time. The proper fix would be, at minimum, to add a compression nut to the drain line so that the two pieces fit together tightly. You will likely need a 2 sized compression nut as shown in the video since one pipe is obviously a larger diameter than the other. You can put the pipe back as it was and fill in with plumber’s putty, but the putty will not hold long if any back pressure is developed due to a blockage further along.
I had already put the pipes together pro tem, and I didn’t notice if the pipe in the wall was PVC or metal, but I think it was metal.
The pipe in the wall does not stick out beyond the wall, so I don’t think any kind of compression fitting or pipe clamp is possible.
If the dried brown stuff was really plumber’s putty, then it was the thinnest application of that I have ever seen – what was left was very scattered and thin, and stuck to the outside of the pipe. I didn’t think that was an appropriate application for plumber’s putty, precisely because it does dry out and lose effectiveness.
I get the part about no pressure on the joint, the pipe slopes down slightly from the P joint to the wall, so it’s just gravity. And yet without anything in the joint it still manages to leak a little.
As for the “why” of this being done, when we remodeled the downstairs that included this bathroom, I had a contractor who didn’t use subs, he had all his own men doing the work. I thought at the time that this was a good thing. Now I’m rethinking, based on the possibility that some of them weren’t properly trained in their supposed specialty. On the other hand, everything passed city inspection, and I assume they would have looked at this joint as well. The bathroom was the only plumbing they would have had to inspect.
I would cut a hole in the wall to expose the drain pipe, and see what is going on.
It’s easy to repair drywall, and it should be hidden, so even if you do a sloppy job, so what?
No, there’s no slip nut like in your picture. There is a thin brass 6-sided nut just inside the wall. From what I can see, I don’t think that had anything to do with holding the joint together, I think it’s holding the pipe inside the wall in the proper position. That’s more or less a guess on my part.
I’ll see about taking a photo tomorrow. I’ve put the pipes back and tried to force some plumber’s putty into the joint, although there is precious little space for it, the fit is pretty snug. The joints seem to be holding so far, but tomorrow I’m going to see about getting some water sealing tape just for good measure.
It sounds like you have all of the normal under-sink things with a brass tee in the wall, and a brass slip nut like this one. No handy wings for finger-tightening like the PVC ones have.
Someone probably cut the pipe between the trap and the wall too short, and with the slip nut mostly buried by the drywall, they got lazy and tried to glue it together with putty.
Yes, good idea. In fact, cut that piece of drywall so it’s like a trapdoor, with holes/slots where the pipes go thru. Cover the edges with a nicely-painted 1 x 2 (or even skip the painting, if it’s hidden). That ‘access panel’ will be greatly appreciated by a plumber (or by you) someday in the future.
And it really sounds like you have to get into the wall to fix this up to code. Silicone or similar would probably work fine for years (as old plumbers putty did), but it’s not the ‘right’ way.
