Re-tapping female ABS fitting


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Old 07-18-16, 12:11 PM
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Re-tapping female ABS fitting

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Size:  49.5 KBMy metal tub drain stop screws into the 1-1/2" female ABS drain fitting (under the tub). Unfortunately, the ABS threads have become cross-threaded, and the stop is not screwing in. Is there a way to re-tap the ABS threads so I don't have to take everything apart again to replace the ABS fitting?Attachment 68582 (note: photo is before a very arduous installation with limited access to the drain)
 
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Old 07-18-16, 02:26 PM
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I have never tried to tap ABS threads. I have used a tap to "clean out" old cast iron threads enough to screw in a brass nipple.

There's no guarantees here. I would not try to tap the fitting, only clean it up to where you can get a nipple started. Use tape and Teflon paste on the male threads of the nipple (drain) when assembling.

If you can't get a nipple started I would cut the drain pipe and use a shielded no-hub coupler to replace the shoe and connect it to the existing waste arm, you have room and the no-hub can be trusted to be leak free if installed properly.
If you need to use a no-hub, cut the pipe going into the Tee no shorter than 1" and tighten the screws to 60 inch pounds.
 
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Old 07-19-16, 01:05 PM
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Thank you for the advice.
Unfortunately, I have no access to the drain without removing kitchen cabinets and breaking through the kitchen wall to get to the drain in the adjacent bathroom. I was trying to avoid that, but it's looking more and more like that's the route I'll have to go. Before going there, one last idea: does anyone make a drain fitting (the screw in part) with the metal strainer but a plastic or ABS threaded nipple? I feel like ABS on ABS would be easier to get started when screwing it in through the drain hole.
Thanks
 
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Old 07-19-16, 01:50 PM
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I think metal threads will screw in much better than any type of plastic.
Here's an idea:

Purchase a long (6" or so) brass nipple. Use brass because it has high quality threads.
Use the nipple to practice getting the threads started and inserted. The brass is expensive but might be worth it if it works.
 
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Old 07-19-16, 03:23 PM
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You might be better off using a thread restoring file, 1-1/2 inch pipe has 11-1/2 threads per inch. Here is one from Amazon although the shipping charge is a bit steep. You might find one locally at a GOOD hardware store or a place that caters in tools. https://www.amazon.com/TF-7-Thread-R.../dp/B0020J7NXQ
 
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Old 07-19-16, 03:51 PM
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Yes, I'll try the brass nipple idea before "Plan B".
Furd -- the links I checked show thread restoring files for use on the male component. They wouldn't work on my ABS part, I don't think. Unless they make a file for the female component?
 
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Old 07-19-16, 05:00 PM
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I have no access to the drain without removing kitchen cabinets
If it comes down to it, it's not that hard to cut out the bottom and the back of a cabinet and replace the material. It's done quite often when replacing a sink base deck.
Usually the new bottom cannot be cut perfectly and you need to add molding to the sides to hide any gaps.
 
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Old 07-19-16, 08:55 PM
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Brian --
actually, that's not a bad idea. It would be much easier than removing the cabinet. When the repairs are finished, I wouldn't have to replace the drywall, just a false back for the cabinet which can be removed again if future access to the tub drain is needed. Thanks!
 
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Old 07-25-16, 08:44 AM
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SUCCESS!!
I checked at Home Depot first, but they didn't have a 1-1/2" threaded brass nipple. They said I could get one at Fergusons or other plumbing supply. But when I told the Home Depot guy (retired plumber) what I needed it for, he said he's run into the same problem many times and uses a 1-1/2" threaded galvanized pipe to 'recut' the threads to get it started. I bought the 4" threaded nipple for less than $4. I cleaned up the ABS threads in the tub drain as much as I could using a small awl and Dremel tool, then tried screwing the galvanized nipple in. The nipple is slightly tapered, and it worked first time!! I was then able to screw in the drain strainer to complete the installation, checked for leaks, and done!
Thanks for all suggestions!
 
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