Teflon Tape Problem

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I have never had a problem with Teflon tape for water pipe joints before. Now I did 4 joints and all 4 leaked, even after tightening them tighter than I have ever had to tighten a joint. I ended up disassembling and using the white pipe dope with Teflon in it. One joint seemed to leak water through the layers of tape! Any ideas what happened? I put 3 layers of tape on as snug as I always do but this didn't hold any of the joints.
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On 9/9/2011 5:38 PM, Michael Dobony wrote:

Did you buy it at a real supply house?
I was helping a friend and he bought some at big box and the texture and behavior was noticeably different than good tape. It didn't wrap properly and took way too much torque. I ended up using some from a box of stuff I brought. Made me wonder if it wasn't recycled or some other material.
I had the same thing happen with home cheepo solder on another occasion. I know how to solder and the solder just wouldn't melt and wet properly.
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They now make different thicknesses of teflon tape. Maybe you got one of the thinner varities. I only use the "heavy duty" variety, which in reality is probably the old standard type we always used.
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Michael Dobony wrote:

Hm, put 3 more layers on, and you might turn out lucky.
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On Fri, 9 Sep 2011 16:38:52 -0500, Michael Dobony

Probably bad fitting threads.
--Vic.
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Steel pipe? Copper? Brass? Fitting made in China?
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On Fri, 9 Sep 2011 23:23:55 -0400, Ed Pawlowski wrote:

Hooking up a water heater the right way (previous owner ran cpvc directly to the water heater). Iron pipe to brass ball valve to brass-to-cpvc fitting, two sets.
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Michael Dobony wrote:

Teflon tape is NOT designed or promoted to be a sealant - it is a lubricant to facilitate joining pipes. (Oil will work almost as well as Teflon.)
It is the deformation of the threads themselves that act to seal the junction.
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On 9/10/2011 8:37 AM, HeyBub wrote:

That's not what it says on the package.
http://www.oatey.com/apps/catalog/instance_assets/assets/Photo/Teflon_Tape_31202.jpg
And actually none of it has Teflon brand TFE according to DuPont.
http://www2.dupont.com/Teflon_Industrial/en_US/teflon_tape.html
So in a way you are correct since there is no such thing as "Teflon Pipe Tape".
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On Sat, 10 Sep 2011 10:01:50 -0400, Tony Miklos

Here's what I've found working with threaded pipe. Probably nothing designed for more than 150 psi. Includes industrial work, paid residential plumbing, and my own stuff. High pressure water/steam stuff like I did in Navy is all welded flanges, with a crushable metal gasket between the flanges. Called the gaskets flexitallic, maybe a brand name. Designed to whatever the pressure needs are. I've cut thread in many pipes up to 1 1/2". Good new threads don't need dope/tape to seal. As HeyBub said, the threads deform. I've gone without dope a few times - can't remember why. With no dope/tape you have to crank more to deform more threads to ensure a seal. Water will rust up the innermost threads, so when you reuse the fitting it's harder to get a seal, dope or not. Both male and female will rust and lose threads, so you don't want that. A doped/taped fitting can be resused numerous times. Thread deformation/rusting is less, because the dope/tape does help seal by filling in thread imperfections. You'll crank it in a little harder with each use.
That's basically a "feel" you develop, but it's not rocket science. New fittings should be easy to seal unless they're cut badly. From watching novices work the main reason I've seen for leaks is simply not cranking it in deep enough. Normally for new pipe you only want 3-4 threads showing at a fitting. Heavier drain pipe might no get cranked in as deep. I've got a number of 50 year old galvanized fittings in this house showing 5-7. They'll fail first. I don't know why people don't crank them as deep as they should be. When reusing some, I've cranked the last thread flush. Valve threads are usually harder metal than pipe fittings, so you want to dope/tape them well. They don't deform as well. But you don't want to overdo the cranking as you can crack the valve casting. You'll know when that happens.
Tony probably got badly threaded fittings, one side or the other. I've never seen a real difference in dope. The old stuff was oil and lead and maybe something else. That would harden up good and the biggest disadvantage was you had to clean it off the upper threads to reuse it. I've been using the tape for years now and it comes in different thicknesses. I wind it tight the entire length of the threads until if fills about a third of the thread depth. Never had a problem with it.
--Vic
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On 9/10/2011 10:43 AM, Vic Smith wrote:

I will second all of the above. Vic, that was a good treatise on threaded pipe. I am a certified pipefitter and a certified pipefitter instructor, and that is almost exactly how I would have described it.
--
Robert Allison
New Braunfels, TX
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Perhaps but I think there is some misleading information the preceding posts.........
"Normal" / "every day" (the kind you buy at HD, hardware store, etc) pipe threads NEED a sealant.
If the threads are cut as NPT threads they CANNOT work (ie no leaks) without a sealant.
Only NPTF (dry seal) pipe threads are designed to work without sealant. My experience (unpleasant) with NPTF dry seal threads was on military hydraulic systems where tape or dope was prohibited.
On properly cut regular (NPT) pipe threads, the crest of the male thread and the valley of the female thread have a designed in (manufactured in) clearance.
No matter how much you tighten the thread there will always be that small gap, the crest & the valley never meet. This gap creates a spiral leak path from inside the fitting to the outside world.
This spiral leak path needs to be filled with sealant of some sort; dope or tape.
NPTF are designed to have a crest / valley interference that deforms and creates the seal.
Here is a link to further explanation of the NPT vv NPTF
http://www.cutting-tool-supply.com/TechTips/Tapping/NPTvsNPTF/NPTVsNPTF.htm
Maybe the crappy NPT fittings sold today can function similarly to NPTF threads but that is not the design intent of NPT threads. :(
HTH
cheers Bob
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wrote:

Agree. It's always standard practice to dope/tape NPT.

See, I don't want to argue about this, because doping/taping is always standard practice. You should ALWAYS dope/tape NPT. But I've seen plenty of undoped non-leaking NPT on residential water supplies. Maybe 50 psi or so. And I know I've done it myself with no leaks, probably for a temporary fix. Sometimes you see rust spots where it seeped but stopped, sometimes not. I figure minerals or oxidation fills the remaining thread gaps. So I was wrong if I gave the impression you could get by with no dope, because that's the wrong way to do it. Also wrong about saying that thread deformation itself will seal. That's all HeyBub's fault. ALWAYS dope/tape NPT.
--Vic
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wrote:

totally correct........ more once I've ignored a tiny leak (drip) on a threaded joint because we have medium hard water. A day later, no drips.
The main reason NPT "can" be assembled without dope or tape is that a lot of water systems have water with calcium carbonate in it.
check out Locite HVAC thread sealer.... http://hybris.cms.henkel.com/henkel/msdspdf?matnr=235535&country=US&language=EN
one of the major constituents is calcium carbonate
cheers Bob
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Vic Smith laid this down on his screen :

First, sorry for taking so long to get back to you. Just got my NG's working again. This is garbage simply because this type of guideline demands precision tapping and reasonable cutting standards. If one cuts too many threads it can bottom out on any female connector that narrows down soon after the threads. Also, the female threads would need to be machined to a uniform standard, but they are not. Therefore one cannot set such a standard as the number of threads showing on a fitting.

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On Sun, 02 Oct 2011 14:34:11 -0500, Mike Dobony

3-4 threads showing is hardly a standard. But it works. I've threaded many pipes with machines and hand-turned dies. Never "cut too many threads." Threading machines have a stop, and with hand dies you thread until the pipe is flush with the die. Look at some threaded pipe at the store. You should see the same number of threads on every one. Can't speak to female fittings. Had some bad ones. Very few.
--Vic
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On 9/10/2011 8:37 AM, HeyBub wrote:

Of course with the notable exception of of anything using NPT (typically found on anything a homeowner might encounter) which require dope/tape whatever by design.
Succinct explanation here:
http://www.cutting-tool-supply.com/TechTips/Tapping/NPTvsNPTF/NPTVsNPTF.htm
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My swimming pool connectors used to leak until I consulted expert Sam at the pool store. He advised (1) six layers of teflon tape over the threads and (3) another three turns at the end of the fitting (where a large hex-shaped moulding appears.) These connections leak no more.
--
Don Phillipson
Carlsbad Springs
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Bob F-
When you mention ......my ongoing troubles with large PVC connections. <<<<<<<<
Threaded PVC to threaded PVC or PVC into metal or metal into PVC?
Two practices that will greatly reduce problems:
1) Never use tape on threaded PVC to threaded PVC; the "extra thickness" can over stress the female thread and create a spitting problem Use Loctite - No More Leaks thread sealant
2) PCV into metal never metal into PVC; the tapered metal thread can over stress the PVC part and induce a splitting failure
cheers Bob
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interesting. I can find it listed for sale, but not on the Loctite site.
http://www.henkelna.com/cps/rde/xchg/SID-0AC83309-7D6A27EA/henkel_us/hs.xsl/full-product-list-7932.htm?countryCode=us&BU=industrial&parentredDotUID=productfinder&redDotUID=0000000I6D
I get mine at McMaster but it's available lots of places online
I
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