The futility that is teflon tape

[HoosierBuddy]

I should have known better.

Trying to install a new chuck on my shop's air line...I've got a male threads from my new hose barb fitting and male threads on my new quick connect air-chuck. NO WORRIES, because I also have an aluminum "hex ******" for lack of a better description that can put it all together.

And...I can't find my pipe dope (thread sealant...rectorseal...whatever you like to call it...to me it's always been "pipe dope").

So, against my better judgement I wrap the treads with teflon tape, put it all together and put 90 PSI on it. A little soapy water and...it's bubbles everywhere.

Long story short...I went through all my cabinets until I found where I had misplaced the dope (that sentence ALONE will probably get me on a watch list somewhere)...botta-bing botta-boom...leaks all fixed.

Turned a 5 minute job into a 30 minute job (mostly getting all the teflon detritus back off the fittings during the "botta-bing" stage above)...but it got done and I learned again what I've known for years.

Teflon tape just doesn't work as well as pipe dope...ESPECIALLY with gases and ESPECIALLY at high pressures and MOST PARTICULARLY with these cheap offshore "almost NPT" threads that we get these days.

sigh.

Phil

 

[aka Larry]

Interesting as I had the opposite affect. When I installed my RapidAir system I decided to use the pipe dope instead (not sure why I decided to switch) but it was messy and it leaked. I replaced it with Teflon tape...no leaks.

 

[70Swinger440]

Not being a ****, but did you put the tape on in the right direction? If you put it on backwards, it unrolls in the threads while you are screwing the fittings together.

 

[CNGsaves]

^ ^ ^ For normal threads . . . . clockwise . . . Righty Tighty / Lefty Loosey

Still irks you off when you wrap the teflon on backwards . . which I've done !!

 

[HoosierBuddy]

I wrapped it the right way.

It does occur to me that the PROPER teflon tape for air might be the yellow (thicker tape) though...which is not what I attempted to use. I know the yellow is used for gas...maybe it would be better for air too.

I know teflon tape works sometimes. I've seen it work. I've used it and had it work. But this isn't the first time I've had zero luck getting it to work. I definitely think that some of these cheap fittings NPT threads aren't formed properly. The Campbell Hausfield $2 thread adapter may be very much at fault here. BUT...a quality pipe dope applied to both male and female threads, allowed to tack and then assembled tightly will seal a lot of places where white teflon tape won't, in my personal experience.

And I agree with aka Larry...pipe dope is messy. For sure.

Phil

 

[Ainsley]

I hate the white Teflon tape, I only use the Orange stuff at work... With pipe dope on top.
Once I started that routine I rarely get leaks.

 

[jonw9]

I hate the white Teflon tape, I only use the Orange stuff at work... With pipe dope on top.
Once I started that routine I rarely get leaks.

Belt and suspenders method.

 

[CJ7VFR]

How many times did you wrap the Teflon tape around the male threads?

You have to make sure you wrap the tape around the male threads more than just one or two times! Four or five times around is a lot better, and I have even seen people suggest as many as 8 times around to create an air/water tight seal.

I use 5 times around, and as CNGsaves said, make sure it wraps the correct way, and I never seem to have a problem.

Now the pipe dope always gives me headaches. Like aka Larry said, I find it to be very messy, and a lot less controllable as to where it is supposed to go versus where it is not supposed to go after I apply it.

But you have to use whatever is best for you, and what you are most comfortable with.

Jim

 

[yaidunno]

It’s not the tape’s fault. The tape is primarily acting as a lubricant between the two fittings, and is doing very little to seal it. You are relying on the taper of said two fittings to perform the actual seal.

As you mentioned though, the quality of the threads, both male and female, is questionable with any offshore fitting.

 

[ddawg16]

it’s not the tape’s fault. The tape is primarily acting as a lubricant between the two fittings, and is doing very little to seal it. You are relying on the taper of said two fittings to perform the actual seal.

As you mentioned though, the quality of the threads, both male and female, is questionable with any offshore fitting.

^^ that ^^

 

[Keel]

Not being a ****, but did you put the tape on in the right direction? If you put it on backwards, it unrolls in the threads while you are screwing the fittings together.

^^^^^^^ this

 

[stikman56]

Interesting ,I prefer it on air stuff. I buy cheap rolls of it to use on the air fittings when I test tools so all I have to do is screw it in by hand and it won't leak. Beat using wrenches on every tool I test, and very effective. I start at the top of the threads go to the bottom and finish at the top and they don't leak.

 

[tab2]

A plumber told me that the pipe dope is for the rseal, the teflon is so that it is easier to take it apart later.

I use teflon only and usually have good results. That doesn't mean that I have to think about it, and then end up putting it on the wrong way anyway

 

[manwithtools]

It’s not the tape’s fault. The tape is primarily acting as a lubricant between the two fittings, and is doing very little to seal it. You are relying on the taper of said two fittings to perform the actual seal.

As you mentioned though, the quality of the threads, both male and female, is questionable with any offshore fitting.

Exactly, it's not a well understood fact that it's intended to lubricate and not to seal. The design of threads is what ultimately causes a leak proof seal. It's important to tighten properly and some cheap fittings cant even withstand the proper torque without distorting. The Teflon tape helps achieve the torque with less metal on metal friction, helping to avoid distortion.

I've used Teflon tape exclusively for years and usually if there is a leak it's because of poor thread fit. Nothing to do with the tape.

 

[2rr2nv]

hmmm, interesting... I've used tape for years and now use it on the job site (coal mine) and nary a problem. If I want it sealed, tape works for me. guess I'm lucky...

 

[akdiesel]

Teflon tape is used through out many of gas services. I have used it alone (white) for pressures up to 6000 psi gas with no leaks. Done right it is a good tool.

 

[vonhef]

Teflon tape is used through out many of gas services. I have used it alone (white) for pressures up to 6000 psi gas with no leaks. Done right it is a good tool.

Same here... tape work great with good fixtures. If "dope" is used on pipe fittings that flow hot oil, it is inevitable that the threads will eventually develop a leak. Use teflon tape, and it holds.

 

[Rickster55]

How many times did you wrap the Teflon tape around the male threads?

You have to make sure you wrap the tape around the male threads more than just one or two times! Four or five times around is a lot better, and I have even seen people suggest as many as 8 times around to create an air/water tight seal.

I use 5 times around, and as CNGsaves said, make sure it wraps the correct way, and I never seem to have a problem.

Now the pipe dope always gives me headaches. Like aka Larry said, I find it to be very messy, and a lot less controllable as to where it is supposed to go versus where it is not supposed to go after I apply it.

But you have to use whatever is best for you, and what you are most comfortable with.

Jim

I go with 5 and rarely a problem.

 

[ez-duzit]

...I only use the Orange stuff at work... With pipe dope on top.
Once I started that routine I rarely get leaks.

You can continue getting mostly leak-proof joints using your backyard method, or you can use what the pro's use and eliminate leaking joints altogether--Leak Lock.

 

[HoosierBuddy]

You can continue getting mostly leak-proof joints using your backyard method, or you can use what the pro's use and eliminate leaking joints altogether--Leak Lock.

We switched to Leak Lock at work a few years back. It's great until you need to take the joint back apart...then it's very hard to disassemble. About 2 years ago we switched to Rectorseal #5. In 5 more years maybe we'll switch again.

To the tape lovers...I must say I've never used more than 3 wraps...so that may be my issue. Next time I can't fine my pipe dope...maybe I'll try that.

Phil

 

[dutchgray]

Use plenty wraps of tape and it works well with decent fittings (which here means PCL) but our fittings are BSP and not NPT.

 

[rlitman]

How many times did you wrap the Teflon tape around the male threads?

You have to make sure you wrap the tape around the male threads more than just one or two times! Four or five times around is a lot better, and I have even seen people suggest as many as 8 times around to create an air/water tight seal.

I use 5 times around, and as CNGsaves said, make sure it wraps the correct way, and I never seem to have a problem.

I'm with you. With white teflon tape, less than four wraps is a waste of time. 5-6 works for me. But when I do use tape, I prefer to use the pink tape. It is much thicker, and only requires 2-3 wraps.

For permanent connections, I use Rectorseal 5. I reserve tape for places where I don't want the potential mess.

Not mentioned in this thread, but possibly the best thread sealant I have ever seen, is the teflon that comes in crayon form. I have not found anything superior to this, and I keep a couple around for "problem" areas (such as union and flare seats where tape and dope are completely inappropriate).

It’s not the tape’s fault. The tape is primarily acting as a lubricant between the two fittings, and is doing very little to seal it. You are relying on the taper of said two fittings to perform the actual seal.

This piece of apocrypha comes up time and again. NO!
There is a helical leak path at the root of NPT threads. NPT is not designed to deform upon mating, so no matter how much you tighten it, it will not seal without something else in there. In this case, it is the tape or the dope that completes the seal. Yes, NPTF does deform, and can seal without any filler, but this only works on brass threads (hence, NTPF is not used on steel fittings, and if a steel fitting needs to seal without any filler, something other than the threads must make the seal).

 

[Stevie-Ray]

Teflon tape for me, normally, and I never have leaks. At least 4 or 5 wraps, same way we did it at work, always.

 

[yaidunno]

This piece of apocrypha comes up time and again. NO!
There is a helical leak path at the root of NPT threads. NPT is not designed to deform upon mating, so no matter how much you tighten it, it will not seal without something else in there. In this case, it is the tape or the dope that completes the seal. Yes, NPTF does deform, and can seal without any filler, but this only works on brass threads (hence, NTPF is not used on steel fittings, and if a steel fitting needs to seal without any filler, something other than the threads must make the seal).

Well, can't really argue the logic behind that (helical path along the root of the thread). I will cease the spreading of **** on the internet. My apologies, didn't mean to be "that guy".

 

[overkill 19]

I'm a power engineer I use Teflon all day long at work from ethylene to hydrogen fittings, never use dope.
And sorry if it comes across as pompous but leave the first 2-4 threads bare. And correct rotation. You only need 3 wraps maybe 5 at most. Your fitting is tapered so you need threads engagement. Meaning you need most of your male threads inside the female threads. Or 3/4 of them. I bet your using too much tape and only getting your fitting buried 1/4-1/2 way.
If you have new fittings 3 wraps should be good.

Look at how much your threads buried in with pipe dope compared to Teflon.

 

[LS6 Tommy]

I wrap a little more than normal, too, but most manufacturer's instructions for PTFE tape say no more than 3 turns, some say start at the **** of the threads and wrap in the opposite direction from the way the fitting is turned when fitting the joint. Most also say NEVER use both tape and dope, but I have never read any type of an explanation as to why.

Tommy

 

[Gerald O]

...This piece of apocrypha comes up time and again. NO!
There is a helical leak path at the root of NPT threads. NPT is not designed to deform upon mating, so no matter how much you tighten it, it will not seal without something else in there. In this case, it is the tape or the dope that completes the seal. Yes, NPTF does deform, and can seal without any filler, but this only works on brass threads (hence, NTPF is not used on steel fittings, and if a steel fitting needs to seal without any filler, something other than the threads must make the seal).

You are still as wrong as the last time we argued this.
http://www.garagejournal.com/forum/showthread.php?t=268698

NPT threaded fittings are in fact designed, when the threads are properly cut, to deform at the ends for the seal. This is stated by the manufacturers themselves. It is a different sealing mechanism than NPTF, but nonetheless is still an intentional deformation seal.

Teflon tape is intended as a lubricant, not a sealer.

 

[Brian_WK]

I use both. I also use the Blue Monster tape and Leak Loc Both are blue so they match . Zero leaks from Natural gas to water to 410 refrigerant to 4500 psi air fittings. I started doing both about 6 years ago before I would get leaks if I just used one or the other especially on black pipe fittings the threads are nicked, missing and garbage.

Brian

 

[Elginz]

I used to assemble fire suppression units sold to the military. Quality fittings, two wraps (inspected by government inspectors), no leaks. We tested with 250 psi air. If there was a leak it was after sandblasting and in the side of a fitting, not the treads.

 

[DekeT]

It’s not the tape’s fault. The tape is primarily acting as a lubricant between the two fittings, and is doing very little to seal it. You are relying on the taper of said two fittings to perform the actual seal.

As you mentioned though, the quality of the threads, both male and female, is questionable with any offshore fitting.

As others have mentioned, this is the correct answer. Teflon tape is a thread lubricant not sealer.

 

[Stuart in MN]

You only need 3 wraps maybe 5 at most. Your fitting is tapered so you need threads engagement. Meaning you need most of your male threads inside the female threads. Or 3/4 of them. I bet your using too much tape and only getting your fitting buried 1/4-1/2 way.
If you have new fittings 3 wraps should be good.

This is what I've found as well - more often than not, people put too much tape on the fittings.

 

[JerryB]

Semi-retired now, but I spent nearly 50 years designing and manufacturing high precision gas and liquid process systems. First 10 years was in aerospace where I first started using teflon tape for systems with pressures ranging from hard vacuum to extremely high pressures (in the 3000psi range). These systems used a wide variety of gasses and liquids, including helium and hydrogen. Then over 40 years in the semiconductor equipment industry where extreme leak tight was 100% necessary. I probably specified and oversaw the application of thousands of miles of teflon tape!

In all that time, there were very few cases when a properly prepared and assembled joint had startup leaks or failed in service. We just could not stand to have leaks or rework. The few failures that did occur were usually the direct result of improper tape application, or (occasional) machining defects. Training and supervision solved the improper applications, and careful vendor selection and quality control solved the machining defects.

Of course our components were virtually 100% American made, and to the proper specified tolerances. Suppliers like Swagelock just did not deliver any fittings that were out of spec.

In the current market, there are such a wide variety of tapes (too thick, too thin, too weak, too tough, etc.) and threads (many Asian produced with little QC) that we shop folks are challenged to make a good joint.

I am currently the technical director for a small domestic water system. Our plumbers mostly like putting a layer of tape, then a layer of RectorSeal in the joints. These are mostly 1 1/2" and 2" pipe where the male part is PVC and the female part is brass or steel. Pretty good, but not 100% results, mostly due to the above QC factors.

As to how to make a good small (1/8" to 1" ips) pipe joint, the fittings have to be in spec, burr-free and no rust. No chuck marks across the threads. Start with the edge of the tape just shy of the male end of the thread, and wrap 1-1/2 turns in a clockwise direction. Best is to use a tape that will allow you to pull it in two rather than requiring cutting. Pulling it to break it helps snug it into the thread grooves. Then carefully assemble the joint without disrupting the tape.

A couple of common problems are tapes that are way too thick for the size joint being assembled, and folks that use way too much tape.

Just my take and experience.

 

[Karl_B]

On my air fittings, I just use two layers of tap and get the joints good and tight. They don't leak at the threads, even on my cheap Harbor Freight fittings. They do leak where they couple together and I won't buy those cheap fittings again...

 

[overkill 19]

Semi-retired now, but I spent nearly 50 years designing and manufacturing high precision gas and liquid process systems. First 10 years was in aerospace where I first started using teflon tape for systems with pressures ranging from hard vacuum to extremely high pressures (in the 3000psi range). These systems used a wide variety of gasses and liquids, including helium and hydrogen. Then over 40 years in the semiconductor equipment industry where extreme leak tight was 100% necessary. I probably specified and oversaw the application of thousands of miles of teflon tape!



In all that time, there were very few cases when a properly prepared and assembled joint had startup leaks or failed in service. We just could not stand to have leaks or rework. The few failures that did occur were usually the direct result of improper tape application, or (occasional) machining defects. Training and supervision solved the improper applications, and careful vendor selection and quality control solved the machining defects.



Of course our components were virtually 100% American made, and to the proper specified tolerances. Suppliers like Swagelock just did not deliver any fittings that were out of spec.



In the current market, there are such a wide variety of tapes (too thick, too thin, too weak, too tough, etc.) and threads (many Asian produced with little QC) that we shop folks are challenged to make a good joint.



I am currently the technical director for a small domestic water system. Our plumbers mostly like putting a layer of tape, then a layer of RectorSeal in the joints. These are mostly 1 1/2" and 2" pipe where the male part is PVC and the female part is brass or steel. Pretty good, but not 100% results, mostly due to the above QC factors.



As to how to make a good small (1/8" to 1" ips) pipe joint, the fittings have to be in spec, burr-free and no rust. No chuck marks across the threads. Start with the edge of the tape just shy of the male end of the thread, and wrap 1-1/2 turns in a clockwise direction. Best is to use a tape that will allow you to pull it in two rather than requiring cutting. Pulling it to break it helps snug it into the thread grooves. Then carefully assemble the joint without disrupting the tape.



A couple of common problems are tapes that are way too thick for the size joint being assembled, and folks that use way too much tape.



Just my take and experience.

^^^^^Ditto!!
We look for leaks in our plant in the PPB range " parts per billion " for environmental reasons mainly but also so we don't blow our selves up!!! Lol
Ethylene and H2 are out 2 toughest gasses to seal fittings on, H2 prob #1 aside from TEAL which is very easy to spot a leak!

 

[Iggi]

I have always had good luck with the teflon tape. I also used teflon tape to wrap aluminum or copper shield around the audio cable i build. Works great.

 

[Farmall Cub]

I am sure quality of tape has diminished lately. Buying your tape from a good commercial supplier is probably the way to go. At least maybe increase your chances of getting a better quality.
I was a Master Plumber by trade for years and no more than three wraps was the norm on fittings, gas or water.
I also backed that up with dope (good dope like Rectorseal). Never had much of an issue. Running black iron pipe in a house or small commercial we never used tape but we were cutting out own threads too. Occasionally you'd get a sand hole or bad casting in a larger fitting (schedule 40) that would leak.
But all lines had to be tested, cheap dope was never an option.
That said, I just plumbed up my compressor with 3/8" fittings from Lowes and they are ****. I am suprised it does not leak first time out.​

 

[rlitman]

You are still as wrong as the last time we argued this.
http://www.garagejournal.com/forum/showthread.php?t=268698

NPT threaded fittings are in fact designed, when the threads are properly cut, to deform at the ends for the seal. This is stated by the manufacturers themselves. It is a different sealing mechanism than NPTF, but nonetheless is still an intentional deformation seal.

Teflon tape is intended as a lubricant, not a sealer.

Then we'll have to agree to disagree. But if your supposition were correct, then oil would work better than pipe dope.

 

[brownsmustang]

Then we'll have to agree to disagree. But if your supposition were correct, then oil would work better than pipe dope.

Actually oil wouldn't be a better option. For one very few things have less friction than teflon. Second, oil contamination could be very dangerous in some applications. Third the oil would eventually dry out allowing the possibility that the joint could stick together permanently. Teflon is a lubricant.

Edit:
I just realized you said "pipe dope" I believe dope works differently than tape, but some have teflon in them for the same reason, a lubricant.
Scott

 

[Fueler]

For several reasons I have graduated to using the Blue Loctite on any automotive, machined brass or air line fittings. No problems that way and they still can come apart later.

I use pipe dope on the black pipe from the big stores. Nothing else works on what someone called "almost pipe thread". True that.

 

[rlitman]

Actually oil wouldn't be a better option. For one very few things have less friction than teflon. Second, oil contamination could be very dangerous in some applications. Third the oil would eventually dry out allowing the possibility that the joint could stick together permanently. Teflon is a lubricant.

Edit:
I just realized you said "pipe dope" I believe dope works differently than tape, but some have teflon in them for the same reason, a lubricant.
Scott

I'm not at all suggesting that oil can be used to lubricate an NPT fitting to allow it to be tightened to the point that it seals. It seems that the point went over your head, but ok, let's talk about oil.

You say oil contamination can be very dangerous. I say, so what?
I suppose you're not aware that almost all pipe dopes contain oil? You've never noticed it floating on top if you forgot to stir it?
If you're working with sealing an oxygen enriched environment (or perhaps something else sensitive to oil), you should damn well know what you can and cannot safely use to seal your pipe fittings with and not be misunderstanding advice read off the internet before you kill someone.
Also, not all oils will dry out. But I guess you're not aware of this... Anyway, it's so far besides the point, I'm letting it drop at that...

Now let's talk teflon. Saying few things have less friction than teflon completely misses the mark. Teflon fails in the extreme pressures seen between tightly engaged threads. It squeezes out, leaving plenty of metal to metal contact. You can see the results of this when you take apart a connection sealed with teflon tape. What is left behind is a bunch of teflon strings that collected together at the root of the threads.
So why don't we have teflon coated transmission gears, or teflon ice skate blades, or so many other things for that matter? Because teflon isn't all it's cracked up to be.

What teflon IS, is pretty damn inert. And that's quite useful in a number of situations.