pipe fitting question?

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sjh

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1. When assembling galvanized pipe sections, how tight do they have to be? Is it how tight or the Teflon tape that makes the seal?

2. 1st elbow of a run of pipe I just installed has a small amount of seepage, about 2 tbs in 24 hours. :mad: It is on the HARD water side of a water softener feed line located in a garage. It would be a pita to remove everything to redo the connection. I know what I should do, but what are the chances the minerals in the hard water will seal the leak over time?
 

Jimbo

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1. very tight. In theory, the tapers of the threads on the nipple and the socket become perfectly mated and seal themselves. Metal to metal seals are used in lots of places, like unions, and can work. Pipe threads are not quite that good, and in practice, a sealant like the teflon tape, or joint compound, or BOTH, need to be used.


2. very slight chance. It has happened, but if it does seal, it may open up again just when you least expect it.


Why did you do any of this in galvanized? Brass, or copper tube, would be better choices. You can use dielectric couplings when joining copper to existing galvanized.
 

Ian Gills

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I just fitted a brass elbow to my garden faucet and had the same problem. I was very surprised just how good you need to get the teflon and the pipe dope to avoid a leak.
 

Herk

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In theory, the pipe dope or teflon tape is there to lubricate the joint - the threads do the sealing. Galvanized fittings are malleable enough to stretch a bit when the thread screws into them, so overtightening isn't a plus.

The problem arises when threads are not cut cleanly or tapered properly. Like everything else, the quality has deteriorated. Companies cut back on costs by using their threading dies longer; steel is manufactured from recycled batteries and bumpers; standards of quality vary depending on where the product is made. If you used foreign galvanized pipe, expect a life of perhaps six years.

And sealing brass threads is even more difficult - for example a brass fitting screwed onto a copper adapter can be difficult because of the dissimilar metals causing binding or going out of round. Good pipe dope is the answer here, and a good feel for the work is important. When some people pick up a tool they become a danger to their surroundings. That's only one of the many reasons why people "in the business' are usually better at it than any amateur can be.
 

CHH

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When making up pipe connections it is important that the connection be tight enough but not too tight.:)

How's that for a description? Fairly useless? Yup. With threads these days it's hard to tell someone exactly how much torque (knowing pipe diameter would help) is needed or how to tell when a connection is tight enough.

Start with cleaned and inspected threads. Use a wire brush for cleaning the threads and they should be shiny. Minor damage can usually be dressed out with a triangle file or (gasp) a hacksaw blade.

Appropriately rated thread tape and/or pipe dope should should be applied. Folks used to say use only one or the other but some (many?) are now recommending both. Watch the excess thread tape - it can gum up the works if it gets inside piping (maybe not a problem with potable water systems but a real problem with fuel systems).

Start the joint by hand and depending on thread quality it should be made up 3 to 5 rounds (or so) by hand. If only makes a round or two then there may be a problem with thread quality (or maybe just a bunch of tape and dope on the threads). Select the appropriate wrench handle length and make up the connection "pretty darn tight." For 1/2 and 3/4 I generally use a wrench in the 12" to 18" range. The 12" is a bit on the short side so then I have to go "really darn tight." Back when I did this stuff every day it was no problem getting connections tight with the short wrench. These days I tend to use the longer handles for final tightening.

Always keep at least rough track of the number of turns. If only a couple threads are engaged then the joint lacks mechanical integrity. If in doubt, disassemble and inspect. It's better to do it at the time of make-up rather than come back later to fix a drip (as you now know).

Still no real answer about torque. Bummer. For a rough idea look up SAE bolt torque requirements. Brass, aluminum, and plastic will require less torque. Stainless may require more or less and it's liable to gall anyway.:)
 

sjh

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Leak stopped . . .

100% after (2) weeks. The last (1) week there was just dampness. Too lazy to pull it a part and redo it correctly.:eek:
It is in a place visible when I get out of the car, so I will keep an eye on it.
 
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