Correct way to replace sink drain pipe?

[its_a_me]

The 4” male-male pipe leading from where my sink drain connects to the pipes inside of the wall is totally rusted in the bathroom side.

I poked a hole in the plaster and can see where it screws in to the T in the wall. I was planning on replacing it with a new galvanized steel pipe, then running PVC up to my new sink from the galvanized I’m going to install.

Is this the best practice, or can I skip steel and go with PVC fRom The wall?

I’m brand new to plumbing so any help is appreciated!

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• its_a_me
• Dec 1, 2019

Rusted drain pipe from sink

1CC6D982-24B2-4CAF-AC76-18A2214BDCEA

• its_a_me
• Dec 1, 2019

Brightened to show inside the wall, where the connection is.

 

[havasu]

Man, that is going to be a delicate job. Twist off a bit too hard, and it may break off in the wall, but that is your best option. Maybe some of the experts may have a better idea?

 

[Jeff Handy]

Pros on here can hopefully contribute their advice.

Meanwhile, yes it would be ideal to just unscrew the rusty galvanized nipple that is attached to the tee behind the wall.

You can trim out more of the plaster all around it, so you can reach the tee fitting to squirt penetrating oil all around the edge.
Apply it several times, over a few days, and tap lightly all around the edge with a metal tool, the vibrations help the oil get absorbed.

Then hopefully the nipple will unscrew without massive force.

Too much force can twist the tee and wreck the pipes leading from it, up to the vent and down to the drain line.

And leaks or breaks can occur far from the tee.

I think I would be conservative, and if it does not unscrew pretty easily, I would consider cutting out the tee and attaching a new pvc tee with no-hub couplings.

A set of no-hub couplings can join the old galvanized piping to new pvc pipe stubs, that are glued into a new pvc tee.

You will have to enlarge the hole in the wall to about a foot tall vertically.

You can cover the scar with a thin piece of decorative wood trim.
Or just cut your existing wood paneling carefully along a molding line, then later on fill the saw cuts with wood filler or paintable bath caulk.

 

[Jeff Handy]

https://www.amazon.com/Fernco-PNH-22-2-Inch-Standard-Coupling/dp/B000BQ8ALY

The openings leading up and down from the tee are probably two inch.
But one or both might be 1-1/2 inch.
Either way, the process is the same.
You can get these fittings everywhere.
You can find vids of how to join pipes with Fernco no-hub couplings on Youtube.
Very simple and obvious process.

Then just glue in a short stub into the middle of the tee, to replace the rusty nipple.
Cut it off about an inch or two from the wall.
Glue on a trap adapter coupling.
You are done.

 

[CT18]

That is either 1 1/2" or 2" pipe. You need to check to see if the bottom of that nipple is rotted as it looks pretty bad. As a few people have said you want to tread lightly as it could turn into a can of worms. If it were mine and i could not back it out of the tee in the wall and the pipe is in good shape i would cut it a couple inches back from the tee and put a shielded band and run pvc.

 

[bbp]

Cut pipe 1" or so from tee. use a sawzall to CAREFULLY cut through nipple on top from the inside, be aware of the female threads in the tee. When you get close crimp with channel locks,folding in nipple, and unscrew.

 

[Jeff Handy]

I would add, “Crimp with huge channel locks”

 

[Riickk]

That rotted galvanized pipe looks like a twin to what I found under my kitchen sink.
I used a no-hub adapter to route the new plastic P-trap from the disposer.
Since then, water into (turned-off) disposer sometimes backs up into sink.
Never happened before - I had to remove rotted 90 elbow at that pipe's end & probably shook loose ton of rust in that age 60 pipe. Is an intermittent blockage possible??
Methinks I need to get rid of that piece of pipe, and ditto for the OP.

 

[its_a_me]

Thanks so much for the help! Going to assess all the ideas and see where it takes me.