Capping unused galvanized pipe nipple

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VanTry2DIY
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Capping unused galvanized pipe nipple

Post by VanTry2DIY » Sun Mar 31, 2019 1:03 am

Good day all! Today, what should have been a simple reverse osmosis water filter system install under the kitchen sink has ballooned into a minor plumbing emergency thanks to my 49 year old house's galvanized pipes and questionable plumbing decisions by past owners. A short section of the cold water pipe (maybe 4" max) leaves the wall connecting to a T-fitting with galvanized nipples attached to either side. As I learned the hard way, the shut-off valves attached to both of these nipples were shot and did nothing to restrict the flow of water. Both valves have been removed; the right-side nipple connects to a T-valve (pictured) that came with the new RO system which will split the flow between RO and the kitchen sink. The left-side nipple is no longer needed and suffered damage to its threads while removing the shoddy valve still seen in the pics. The house's water is off until I can get it plugged or rework this somehow.

The best answer is probably to ditch all this and re-pipe with a more modern material; I have long-term plans to do this throughout the house but need the water back on ASAP.

I also considered removing the T fitting, but it is frozen solid even after some WD-40 and as much force as I'm comfortable putting on it in either direction. This would also required removing or cutting the nipples due to the close proximity of the PVC drain pipe immediately under it, all of which could jeopardize the pipe in the wall.

For now, I need a new idea or a way to permanently cap/plug this left-side nipple which will never be used again. I've considered some kind of epoxy/filler with a dresser or fernco coupling to a plug of sorts. Note there is not much space left of the nipple before the hot water pipe is in the way.

This is my first plumbing work aside from PVC for the pool. I would love any opinions from the more experienced minds here and really appreciate this forum and Shannon's videos--both have been instrumental for some of my past projects. Thank you!
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A. Spruce
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Re: Capping unused galvanized pipe nipple

Post by A. Spruce » Sun Mar 31, 2019 9:59 am

This is the problem with galvanized pipe, it corrodes and becomes impossible to break joints without doing further damage. Your best option would be to salvage the damaged nipple and either cap it or install a new valve. Give us a pick of the damaged nipple threads.
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VanTry2DIY
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Re: Capping unused galvanized pipe nipple

Post by VanTry2DIY » Sun Mar 31, 2019 10:43 am

Here's a couple shots of the left side nipple. Hard to tell from the pics, but the face of it is uneven. I'm wondering I can hacksaw it to be even while still having enough thread left for a cap.
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A. Spruce
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Re: Capping unused galvanized pipe nipple

Post by A. Spruce » Sun Mar 31, 2019 11:05 am

The end of the nipple doesn't matter, that is not the sealing surface, the threads and pipe diameter are. If you look at the side view of a pipe nipple, you'll see that the threads are on a slope, as you tighten, the nipple gets wider, forcing itself outward against the sides of the mating fitting.

Clean the threads as good as you can, tape it up with teflon tape AND pipe thread compound, thread on the new fitting/valve/cap, whatever you choose to use and snug it up nice and tight. Test your work, if it leaks, give it more tightening force until it stops. You do have to be careful just how much force you use because you can twist off the pipe or nipple because the corrosion has compromised its structural integrity. It doesn't look like your pipe is too bad, but you still want to exercise caution.
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Shannon
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Re: Capping unused galvanized pipe nipple

Post by Shannon » Sun Mar 31, 2019 6:22 pm

I agree with Spruce here that nipple does not look to bad have you tried to thread on a valve or cap?
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VanTry2DIY
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Re: Capping unused galvanized pipe nipple

Post by VanTry2DIY » Sun Mar 31, 2019 6:46 pm

Thank you Spruce and Shannon for the input. After hacksawing off the worst of the unevenness, I've tried a 5/8" brass cap, a 5/8" flared brass cap, and a 5/8" steel ball valve (could not find steel caps at my Home Depot). Of those, only the flared brass cap would thread, and even with teflon plus pipe sealant there was no level of tightness that stopped water escaping.

Here is a couple pics that might better show the condition of the threads; I assume the rear of the nipple is in similar condition but can't get an adequate pic.
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VanTry2DIY
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Re: Capping unused galvanized pipe nipple

Post by VanTry2DIY » Sun Mar 31, 2019 6:52 pm

Here are the exact parts I attempted to use, very open to suggestions. Correction on the valve, it is a 1/2" compatible angle valve.
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A. Spruce
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Re: Capping unused galvanized pipe nipple

Post by A. Spruce » Sun Mar 31, 2019 7:00 pm

I can't tell you what you have to work with. What I can say is that here in the states, exposed galvanized plumbing is usually 1/2", not 5/8". If I had to guess, 5/8" is probably a hose fitting and different thread altogether.

Again, not knowing for certain what you're working with, you would be better off with a galvanized cap over a brass cap. If there is anything left of the valve that you removed, I'd take that to the store and match the size/thread to that, over using a brass cap. Take the old valve and screw in different nipples until you find the right size that you're working with. In my 30 years in construction I've never seen 5/8" galvi pipe.
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VanTry2DIY
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Re: Capping unused galvanized pipe nipple

Post by VanTry2DIY » Sun Mar 31, 2019 7:09 pm

I completely understand and should add a disclaimer that I am not up on plumbing terminology. As a test, I tried screwing on the old valve without success. I'm fairly certain there are breaks and collapsed portions in the nipples threads.

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Re: Capping unused galvanized pipe nipple

Post by A. Spruce » Sun Mar 31, 2019 7:21 pm

Once pipe threads are tightened, they become a bit distorted. The male nipple shrinks because it is squished by the female threaded portion which expands because the male portion is forced into it.

The old valve should still thread on, even though you nipped a few threads off with a saw. It's possible that you took off too much, in which case you either have to replace the existing nipple, or add more threads with a pipe die.

In all honesty, it's a flip of the coin which is the better way to go. If you can't budge the current nipple, then any further attempts at removal will simply destroy it beyond redemption and cause you a whole bunch of headaches trying to find a place to stop replacing pipe. A pipe die and handle will run you around $100, expensive to salvage a nipple, but cheap in comparison to replacing a lot more pipe or hiring a plumber.

I would first start with what I said before, take the valve to the store and find a pipe that threads into it, then buy a threaded galvanized pipe in that size. When you get back home, the amount of tape you wrap will affect how easy it is to thread on the cap. Wrap the tape as tightly as feasibly possible and give ti 5 to 10 wraps, follow with a bit of thread dope, then install the cap and tighten snugly
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VanTry2DIY
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Re: Capping unused galvanized pipe nipple

Post by VanTry2DIY » Sun Mar 31, 2019 7:35 pm

Since I get the old valve back on, is this a viable tool to tap the pipe?

https://m.harborfreight.com/6-piece-pip ... 20provided

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A. Spruce
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Re: Capping unused galvanized pipe nipple

Post by A. Spruce » Sun Mar 31, 2019 8:00 pm

That link doesn't work for me. As long as the thread cutter is of the same thread/type/dimension as the existing, then it should work. I would start with locating a cap first, if this doesn't work, then resort to cutting more threads
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Re: Capping unused galvanized pipe nipple

Post by Shannon » Sun Mar 31, 2019 10:17 pm

I really think if you get a proper sized galvanized cap like Spruce suggested it will thread on. Using the old valve to find a pipe that fits it and then using that pipe to find the proper cap is the best suggestion. Pipe thread is generally pretty loose fitting so get the cap and thread it on without any tape or thread goop. This will ensure it fits and also clean up the threads a little. Then thread it off and use thread dope appropriate for drinking water pipes and apply it to the threads and put the cap on.
Take a look at the end of the nipple and check the threads where you cut to see if they need a little work to clean them up if the cap will not start on.
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VanTry2DIY
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Re: Capping unused galvanized pipe nipple

Post by VanTry2DIY » Sun Mar 31, 2019 11:55 pm

You guys were right--with some coercing I was able to get the angle valve on; I could feel the threads recontouring as it tightened. Still a slow leak with teflon/sealant and tightening it across all the remaining threads.

Hopefully I can get it sorted tomorrow with a few more wraps of teflon and a proper steel cap. Not sure what I was thinking with the brass fittings, but at least now we can turn the water on long enough for a shower and water refill!

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Re: Capping unused galvanized pipe nipple

Post by A. Spruce » Mon Apr 01, 2019 12:35 pm

Glad you're close to getting it sorted.

Brass fittings are not a bad choice, particularly, the problem is that it tends to be made to fit just about anything, NPT, compression, fine thread, course thread, hose fittings, etc. That means finding the right brass fitting is very difficult if you don't know what you're working with. Going with steel fittings they are all the same NPT thread, so you only need match the right size fitting to the pipe, hence why I recommended taking the valve to the store with you to match pipe size.

At any rate, keep us updated on how things go. 8-)
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Re: Capping unused galvanized pipe nipple

Post by VanTry2DIY » Mon Apr 01, 2019 6:47 pm

One question Spruce and all, should I be allowing any cure time for the fittings before testing?

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Re: Capping unused galvanized pipe nipple

Post by A. Spruce » Mon Apr 01, 2019 8:51 pm

Nope, not necessary because you're not using a curing product to make the seal.
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Re: Capping unused galvanized pipe nipple

Post by VanTry2DIY » Mon Apr 01, 2019 9:12 pm

The cap seems to have worked! It was 1/2" galvanized pipe after all. I also invested in some heavier duty grey teflon tape as the white stuff seemed to be getting shredded by the fittings. No signs of leakage for about 30 minutes now.

I'll be officially be out of the woods once I can confirm it stays dry and get the RO system installed, but that will have to happen later this week--for now we're just grateful to have the water back on.

Huge thanks to both of you for your help on this; you've saved us a plumber's bill that we most definitely could not afford. I really appreciate you guys sharing your time and expertise, it means a lot to us.
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Re: Capping unused galvanized pipe nipple

Post by A. Spruce » Mon Apr 01, 2019 11:50 pm

Glad you got it sorted out! 8-)
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Re: Capping unused galvanized pipe nipple

Post by Shannon » Tue Apr 02, 2019 8:36 am

Glad it all worked out.
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