[harum]

Hello, was wondering about ways to tightly reconnect a bathroom sink drain to the sewage stack (please see photo):



The plastic 1-1/2 in. pipe of the old P-trap was just pushed inside the galvanized nipple without any putty or threaded connection. Somehow it wasn't leaking, the fit was snug. For a new trap I have to install, I (also) want a safe, leak-free connection.

What are my options here? Should I use some sealant or putty? Or should the old (easily over 50 yrs old) nipple be removed and replaced with a threaded one? The new plastic pipe also fits snugly inside the nipple; maybe, because of this, some putty would do?

I worry about this connection also because it will eventually be concealed behind drywall and totally unreachable.

As always, any suggestion is greatly appreciated.
Best wishes, h.

[ma0641]

I would sweat a stub extension to get the pipe out of the wall and then use a shielded Fernco fitting to connect the PVC. If you can't sweat the fitting, you could extend a stub out by using the anaerobic copper adhesives that are like Locktite. These adhesives react with the copper ion. The copper has to have a very fresh surface so sanding the joints clean is a necessity. Home Depot and Lowe's carry a product like this. You have no heat or pressure on the fitting other than drain head. You do not want Sharkbite or compression fittings in a concealed space.

[harum]

I would sweat a stub extension to get the pipe out of the wall and then use a shielded Fernco fitting to connect the PVC. If you can't sweat the fitting, you could extend a stub out by using the anaerobic copper adhesives that are like Locktite. These adhesives react with the copper ion. The copper has to have a very fresh surface so sanding the joints clean is a necessity. Home Depot and Lowes carry a product like this. You have no heat or pressure on the fitting other than drain head. You do not want Sharkbite or compression fittings in a concealed space.

I ended up cutting through the nipple to get it replaced:



You are right, the threaded ring is brass and the pipe segment is copper and connected to the inside of the ring by sweating.

The first couple of turns of the female thread on the waste stack outlet, where that brass threaded ring was, are relatively clean and can be used. The rest are covered by the buildup of either rust, or hardened sewage deposits.

Can the rest of the female thread underneath that buildup be cleaned to be used or it's pretty much gone?

[ma0641]

I ended up cutting through the nipple to get it replaced:



You are right, the threaded ring is brass and the pipe segment is copper and connected to the inside of the ring by sweating.

The first couple of turns of the female thread on the waste stack outlet, where that brass threaded ring was, are relatively clean and can be used. The rest are covered by the buildup of either rust, or hardened sewage deposits.

Can the rest of the female thread underneath that buildup be cleaned to be used or it's pretty much gone?

Use an icepick or triangular file and try to clear out the threads. If you know someone with a pipe threader. try to use a tap to clean the threads.
What is your plan next? Thread in a PVC adapter and PVC stub?
You've been busy!

[massplumber2008]

I don't know... looks like the pipe threads broke off to me?

Are you sure the threads didn't break off? You should see more than one thread after removing the old pipe/adapter.

[harum]

Use an icepick or triangular file and try to clear out the threads. If you know someone with a pipe threader., try to use a tap to clean the threads.
What is your plan next? Thread in a PVC adapter and PVC stub?
You've been busy!!

Thank you again. Haven't decided yet on what to install next. From your comment it sounds like a PVC fitting is a good option.

The previous threaded ring somehow hung without leaking on a half turn inside the cast iron outlet; the rest of the outlet female thread was hidden underneath a thick layer of rust.

[ma0641]

Thank you again. Haven't decided yet on what to install next. From your comment it sounds like a PVC fitting is a good option.

The previous threaded ring somehow hung without leaking on a half turn inside the cast iron outlet; the rest of the outlet female thread was hidden underneath a thick layer of rust.

PVC would be fine but not with 1/2 thread. Remember that the steel is much dense than plastic and will strip the plastic threads. I would get a pipe tap,
Clean the threads out and go from there. Most likely 1 1/4 or 1 1/2". Try Harbor Freight or Northern Tool. No need to go big$$$ since you will probably never use it again. Maybe borrow from a plumbing shop?

[harum]

Ended up using a 1-1/2 in. steel nipple to clear enough thread after using a flat screw driver to scratch off some rust.

Strange thing though, not related to the thread issue: I also tried to put new water shut off compression valves on copper outlets under the sink; and after hand tightening and then an about half turn with wrenches, both valves could still slide and rotate on the copper pipes. Tightened some more to stop movement. Noticed that, after water was back on, on one of the valves, water was seeping from underneath the compression nut on the wall side. I tightened a turn or so more, and the leak apparently stopped.

Was it much more than suggested 1/2 turn because the copper outlets are old and might be worn out? Should I replace the valves or go through the process of replacing the copper outlets? Or is it a matter of finding a tighter compression ring?

[ma0641]

You did right. Sometimes the older copper is hardened and the compression ring has to be really tight. I usually put a dab of plumbers grease on the exterior of the ring so the compression nut can tighten easier and not gall the ring. You can actually make a thread chaser by cutting a slot across the nipple and then very slightly bend the nipple in a vise, it will cut through the crud. Then you can put in a replacement nipple. Sounds like you are on your way!!