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-   -   How tight can a brass nipple be installed? (http://www.diychatroom.com/f7/how-tight-can-brass-nipple-installed-34070/)

darsunt 12-19-2008 06:24 PM

How tight can a brass nipple be installed?
 
I recently installed a brass nipple to replace a drain valve on a hot water heater. My first time to install any sort of nipple for a water pressure situation. I screwed the nipple in water tight, then cranked it one complete revolution. I did the same with a hose bib on the nipple.

I still got a tiny bit of moisture leaking thr0ugh. Eventually I tightened both the nipple and the hose bib much more than I was comfortable with, an additional 3 or 4 revolutions for both. Now there is no moisture leak.

Was I right to be uncomfortable tightening the nipple and hose bib so much? Or is it fine to crank these things as much as possible?

TazinCR 12-19-2008 07:15 PM

Did you use thread sealant?

Nestor_Kelebay 12-19-2008 11:49 PM

Darsunt:

If your piping isn't leaking, then I'd just leave it. However, if that piping starts to leak an you want to fix it properly, then....

Take the nipple and hose bibb off, and reassemble using either teflon tape or pipe dope on the threads. Pipe thread is tapered so that any pipe dope or teflon tape between the male and female threads gets "squished" as you tighten the joint, thereby forming the water proof seal. In your case, you tightened the joint enough to deform the metal sufficiently to provide a water tight seal.

Next time, instead of replacing the heater's leaking shutoff valve, just plumb a second valve onto a female hose coupling and install that onto your heater's leaking valve. Open the heater's original drain valve and use the new valve you put on that drain valve from then on.

darsunt 12-20-2008 01:57 PM

I did use teflon tape, two layers on both nipple and bib.

So you really aren't supposed to crank a nipple in so tight? That is what I'm concerned with. The heater is very old, though, so it will have to be replaced soon. It's okay this time if I overdid it.

Aggie67 12-20-2008 03:34 PM

One of my pipefitters is a 300 lb lad from Poland. He is an absolute ox. Once I saw him over tighten an 1-1/4" NPT forged steel threaded plug into a coupling that was welded into the side of a heavy wall tank, using a 24 inch pipe wrench. He split the coupling.

While it is possible to damage the equipment by tightening it down too much, you'd have to be an absolute ox. Your hot water heater tank is probably some grade of carbon steel, so that nozzle is probably your normal steel half-coupling. Being that your nipple is brass, you risk damaging the threads on the nipple before you did anything to the steel.

It's ok to use TFE tape, for sure. For hot potable water lines, our in-house spec calls for Loctite PTFE (first choice), or Rectorseal No. 5 (second choice) thread sealants.

If you jacked it down and it doesn't leak, you accomplished your mission.

AllanJ 12-20-2008 04:04 PM

>>> absolute ox

I don't think anyone is supposed to ever crank anything anywhere near that tight.

What if you had to disassemble it?

Use proper pipe dope or teflon or other sealants.

Nestor_Kelebay 12-20-2008 09:09 PM

Quote:

Originally Posted by darsunt (Post 200589)
I did use teflon tape, two layers on both nipple and bib.

So you really aren't supposed to crank a nipple in so tight? That is what I'm concerned with. The heater is very old, though, so it will have to be replaced soon. It's okay this time if I overdid it.

Maybe use 3 or 4 turns of teflon tape from now on, and you won't need to twist the bygeesus out of it to get a water tight seal.

It's not that you're not "supposed" to crank the nipple in so tight, it's that you shouldn't need to crank the nipple in that tight.


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