Got a stubborn fitting that's leaking under pressure. Normally I put on 6 wraps of PTFE tape. Someone has suggested putting on dope as well. Do you put on less tape if you do this or just the same amount?

 

I rarely use Teflon tape anymore and when I do it is primarily on compressed air fittings.

Six wraps is too much. When I do use tape I use between 1-1/2 and 2 wraps, NO MORE! You can add a paste type thread sealant over the tape but why bother? Just use the paste type sealant from the get-go. I DO like Teflon paste sealants.

I found out many years ago that Teflon tape alone on copper or brass threaded fittings (thread adapters into valves for example) is almost asking for leaks.

 

TFE tape was never meant as a pipe sealer. It was only meant as thread lubricant to facilitate threading the fitting together. But somewhere along the line it was interpreted to seal also. Even the manufacturer labels says its a sealer.

 

I agree with all the above. To me, the tape was designed as an anti-seize only, making removal of the fitting easier down the road.

IF these are compression fittings, no tape should be used. With compression fittings the tape interferes more than it helps.

 

It's just threaded pipe like on a t bar, pressure switch on a nipple, faucet etc

 

Use tape and dope..

When using tape with dope a few turns to cover threads is sufficient..

Any thread product is actually a lubricant and there is no sealant IMO.. These products let you turn the threads in further to make the seal...

Without any paste or tap you would never be able to tighten enough...

Now if its PVC fittings I use tape only... I build it up more ...Its just too slippery and you end up over tightening with paste and tape.

Tape only and thicker...

Metal threads are different..

 

Thread seal tape (Teflon tape) is a thread sealant. It was never intended to be a thread lubricant although it has lubricating properties. It seals by deforming to fill machining defects in a tapered fitting.

The problem with teflon tape is that most people don't know how to apply it properly and quite often the threads that are to be sealed are so poorly machined that the tape can't do the job. If you have a crappy (read made in China) fitting
pipe dope is probably a better choice.

The tape should be applied in 3 wraps in the direction of the threads. I have used thread seal tape in both liquid and pneumatic systems up to 3000#. Properly applied to a decent fitting it is very reliable.

 

Its a lubricant!!!! .

 

Thread seal tape

White General Purpose Thread Seal Tape With PTFE | Thread Sealants | Oatey

It's a thread sealant product that has lubricating properties. It seems strange that if it is primarily a thread lubricant why does everyone market it as a thread sealant?

This argument has been going on here for years. I worked in a test lab for several years. We tested air and liquid, aircraft system components and teflon tape was the only thread sealant we were allowed to use. Pipe dope was considered a contaminant.

At one time Dupont had a web page describing the properties and applications for their thread sealant. It included illustrations and text showing how the tape deformed to fill thread machining irregularities.

 

I think the problem here is one of reality vs theory. All things being equal, yes, it can seal. But that will be on threads properly and fully cut on high quality steel and manufactured pipe to spec. And then fittings being torqued to specifications.

Now compare that to working with what you get from any big box store or plumbing house and using the tools at hand to tighten the fittings. I'll still go with the combo of TFE and dope. And I'll consider TFE as a thread lubricant and not rely on it as a sealant.

The reality is what the professional plumbers here on this site are doing.

 

Its what I do every day...

The question on the NJ plumbing test asks,

" Is teflon paste/tape a sealant or a lubricant?"

If you say sealant you would of got the answer wrong..

 

Read here...

Guidelines For Choosing A Pipe Thread Sealant Â*|Â*Plant Engineering




Its marketing hype.

 

I've been plumbing kitchen and bath sinks for about 15 years. I almost never use tape. If I did use it for some reason, it wouldn't be to stop a stubborn leak, I use Teflon paste for that. The paste is thick and creamy and has great consistency, it doesn't need stirring.

The only place I put tape on a kitchen sink is the strainer tailpiece threads. That nut tends to freeze up over the years and I want to prevent it.

For stuff like galvanized water pipes, I use tape and white pipe dope.

 

Its what I do every day...

You take pictures of pipes? I know people that take pictures of landscapes and animals and other people. I even heard that some take pictures of themselves. But I never heard of someone that specialized in pipe photography.

 

LOL.. Im a pipe fitter/plumber 30 years + ..

I install whole house generators currently. I tap into the gas meters and run pipe to the gen.

I need to take pics of every job for the customers folder..

But I do take pics of myself now and then....lolololol

 

I knew you your avatar would look just like you.

 

Wouldn't be the first time the required answer on a test was incorrect.

I had a science teacher in eighth grade that was nationally recognized for his teaching ability and had a published general science book. He insisted that a refractor telescope used mirrors and a reflecting telescope used lenses. He was absolutely WRONG but if you wanted to get credit for the exam question you had better answer it incorrectly.

Seems to me that the New Jersey plumbing test also requires adding flux to the female fitting before soldering. That is, at least in the smaller sizes, also wrong.

So I'll end this stupid argument by stating that ANYTHING you add to the threads of a tapered pipe fitting will act as BOTH lubricant AND sealant, some things will be better at lubricating and some will be better at sealing. Further, that old BS statement that it is the metal-to-metal surface of the tapered thread that makes the tight seal is just that, BS.

 

Funny you say that.. when self cleaning flux came out in the 80's we did a test.. we no longer cleaned the fittings and only cleaned the pipe end.. Although we did flux both fitting and pipe we were leak free. And saved oodles of labor cleaning all those fittings for said 10 bath homes we were doing..

Heck we were bending copper back then to save on elbows..

I agree to disagree....

 

Mike, I could use fresh dog manure as a thread compound and achieve a better than 90% rate of no leaks. That doesn't mean that dog manure is either a sealant or a lubricant, nor does it mean that dog manure is a proper material to use in making up tapered pipe threads.

Honestly, as badly as Teflon tape is misused I wish it had never been invented.

 

I said in an earlier post that I look at the tape as an anti-seize compound.
To me, anti-seize and lubricant are the same thing.
At some future date, you would like whatever you are connecting to not be dried up, seized, or whatever, so it's possible to remove the fitting without damage.

The anti-seize also helps when tightening, so it's dual purpose to me.

I agree on the overuse. I spend a lot of time removing tape that should have never been on certain fittings such as gas flare fittings and water compression fittings.

 

Well, I have to take issue with this statement. If true why taper the thread? And have you ever tried to seal a pipe thread that was full cut? Can't be done. The whole point of tapered pipe thread is to set up (not guarantee) the metal to metal sealing process. You still need dope or tape or "string" to make the final seal, but without that taper and interference fit you're just wasting your time.

I have to agree.

 

The taper is to allow it to tighten, not to make the seal. It is the joint compound, whether that be Teflon tape, a semi-solid crayon, some type of paste or a liquid that fills the grooves and makes the seal.

SOMETIMES you can get the bare pipe to tighten enough to get it to seal with some fluids. You WILL need to tighten it far more to do so and you will have a huge problem if you ever want to take it apart in the future.

When I worked for the electric utility we used steam cylinder oil and powdered graphite as a joint compound. My daddy would tell me about using litharge (lead oxide as I recall) and glycerin to make a joint compound that hardened to the point where it was impossible to unscrew the pipes a few years later. Old plumbing books mention using white lead and linseed oil paste. I mentioned using dog manure.

The whole point is, that since the invention of tapered pipe threads they have REQUIRED some kind of lubricant/sealer to properly do the job. Whatever is used is BOTH a lubricant AND a sealant. The compounds used are ever evolving and that is why no one uses the older methods today. Teflon tape is simply another in a long line of experiments in trying to find a perfect joint compound. In my opinion Teflon tape should go the same route as white lead or cylinder oil and graphite. The pastes containing Teflon are so far superior to the tape I will NEVER go back to using Teflon tape.

 

Agreed. My statement was "to set-up the seal...". Perhaps my choice of words was confusing.

 

Wish this thread was around a year ago when I replaced my shallow well pump. I used tape & dope on all the pressure fittings, but used only tape (New! Improved! FastTape) on the suction side since it's not under pressure and all the fittings were US-made solid brass with NICE threads. Guess which constantly drips. I didn't know tape (alone) had such a bad track record.