Black iron plug used in bronze shower valve. Help cleaning threads/plugging hole.

[redbeard]

Hello all,

I’m trying to fix an issue on a new (to us) home. The previous owner (or less likely his plumber) plugged the tub portion of a shower valve with what appears to have been a black iron pipe plug. As you can imagine, the plug corroded badly, and began to leak.

Good news – I caught the leak early.

Bad news – I’ve spent over a week trying to remove the plug (most of the plug disintegrated when using a nipple extractor), and then to clean the threads. It seems the closer I get to finishing (I have about 1.5 threads left), the harder cleaning becomes (probably because the remaining threads were furthest away from the water.

Questions –

1) This is a stand-in shower that will never fit a tub. Therefore, there is no need for a screw-in plug. Is there some type of putty that will harden to permanently plug the hole?

2) Would it be possible to solder a large cap over the area?

3) Is there some solvent (I’ve been using vinegar) that will soften the black iron but not damage bronze?

Thanks in advance for any help.

 

[Terry]

There is no putty that will work for that. If you have access to the valve, you may be better off replacing it.
Have you tried threading in a new brass plug?

 

[Sponsor]

 

[redbeard]

Thanks for the reply. Too bad on the putty. It would have saved lots of time. I imagine, there is not enough room on the fitting to solder a cap on the fitting either.

Right now, I only have access to the back of the valve via a hole I made in the plasterboard in the room that is next to the shower. To replace, the valve, I will need to access the front of the valve via the shower. That means ripping out tile that probably is no longer sold. That option is my last resort as I would need to redo the entire shower.

I have tried threading in a new brass plug, but the worst threads in the fitting are those that begin so I can't get the piece to start spinning. I also have a tool to clean threads/rethread but have the same problem.

For now, I will continue to pick at the threads. It is slow but every day I make progress.

Thanks for your help and time.

 

[Reach4]

Thanks for the reply. Too bad on the putty. It would have saved lots of time. I imagine, there is not enough room on the fitting to solder a cap on the fitting either.

How about using a dental pick to clean the first threads, and using a pvc or cpvc plug?

Even better would be to use a thread chaser tap. Be careful not to cross-thread.

I expect you could solder in a plug, but it would take a lot of heat. Would that damage the piece, or is it all metal?

 

[redbeard]

Thanks for the reply reach4. I've been using a steel dental pick for about a week now. Great tool to clean threads, but I need to move slow because the steel can scratch the brass. I tried a brass pick but it was too soft for the iron. I soak the threads in vinegar for a few hours then use the dental pick.

I have a chaser tap but have had trouble starting it. Once the first threads are mostly done, I plan to use that tool to properly clean the threads.

I had not thought of pvc plug. That sounds promising. How would you seal it. Glue? Epoxy? I imagine plumbers tape would not work.

The fitting is all brass but it just occurred to me that the fitting may have rubber seals that would not react well to heat.

 

[Reach4]

I had not thought of pvc plug. That sounds promising. How would you seal it. Glue? Epoxy? I imagine plumbers tape would not work.

PTFE tape and pipe dope that is OK for plastic would give you the best chance of no leak.

In avoiding crossthreading, I like to turn counterclockwise until I feel it click down. Then visually check to see if you are going in straight, then clockwise.

 

[redbeard]

Thanks for tips. I think I'll continue picking at threads and use a brass fitting. I'll report back when done. Thanks for help.

 

[redbeard]

Just wanted to close the loop on this one. After many hours (+20?) of picking at the threads, I finally cleaned them well enough. The brass plug went in well and no leaks for two days. Thanks again for all the replies.

 

[Dj2]

What do you mean you can't replace the rough in from the wall behind?
If you cant access the fasteners that hold the rough in, remove the blocking it's attached to and install a new rough in.
You can scrape the old rough in for another month, and the leak won't go away. You can get very good rough ins for $50-$60 instead of wasting so much time on the old one.

 

[redbeard]

Thanks for the idea dj2. The fasteners for the valve were inaccessible from the backside but, having just now inspected the hole again, I now see that I could have removed the blocking. Doh. That never even occurred to me. I would definitely have used your method had I known.

I work a fair bit on cars and consider myself pretty handy but have never worked with plumbing before. Frankly, given the time I sank into this, I probably should have just removed tile, replaced the valve from the shower side, then replaced all the tile in the shower. My gf has told me she does not like the old tile so I think I will need to replace the tile at some point.

That said, all my scraping left the old threads nice and shiny. The new brass fitting went in well and there are no leaks.

 

[Tjbaudio]

For future reference, several kinds of taps and thread chasers exist. The biggest difference is the tapper of the starting threads. It sounds like you had a bottoming tap. A plug or taper tap may have worked better.