Pipe Dope or Teflon Tape?

Hinman

Do ou guys prefer to use pipe dope or Teflon tape for steam heating purposes like connecting vents etc? Post your answers and reasoning. Any situations where one is better than the other? Thanks.

I feel pipe dope works great but it’s a bit messier than Teflon tape.

Gilmorrie

I prefer pipe dope. When you assemble a threaded joint with Teflon tape, the tape might become shredded and become loose debris inside the pipe, possibly getting lodged in valves or other devices. For that reason, Teflon tape was (and probably still is) prohibited in U.S. submarine propulsion plants. Also, winding the tape on a connection takes me two hands, and if you drop the tape and it unspools, it creates a tangled mess.

Either tape or dope works OK. But either way, it should be applied only to the male threads. Either tape or dope should not -be thought of as an anti-leak sealant, but rather as a thread lubricant, allowing tapered threads to achieve an interference fit with less torque.

ChrisJ

I use thin white tape on vents and chase the threads in the radiator if they're questionable.

For piping dope alone for good fitting clean threads. Less than great threads 3-4 wraps of tape pulled tight and a smear of Megaloc over it for lubrication.

In my experience tape seals better than dope, but dope lubricates better than tape.

To keep both tape, and dope out of the system you should keep both away from the first thread or so.

Honestly, I feel the most important parts are good clean cut threads and proper tightening.

I recently did some gas piping and my test fixture had a Chinese nipple from Lowes in it. That was the only connection that had an issue and I had to keep tightening it. All of the Anvil nipples and Ward fittings sealed fine at 15 PSI. Good NPT threads will seal at 150 PSI without any issues.

KC_Jones

Getting pieces of tape in the system means the tape was misapplied. In reality there should be nothing on the first 1-2 threads, dope or tape doesn’t matter.

I agree with @ChrisJ its all about the quality of the pipe and fittings.

Dave0176

I use both. I use Monster tape and Megaloc pipe dope. Put the tape on first 3 wraps or so, then a little layer of dope, no leaks ever!!! For air vents just a little smudge of dope is all you need

JUGHNE

For me it seems like tape wrapped tightly (in the right direction BTY) stretches down into the male threads more than dope does.
I rotate the pipe in my fingers to really seat it well.
Them some dope on the tape seemly ends up on the female threads. (Blue Monster tape and Megaloc dope)

Brass male threads seem to need less doping and torque, I think the brass threads conform to the steel.
For me stainless steel need more of both, SS unions can be a bear. I believe because of not having the brass seat.

Here we go with another boxer/briefs discussion.

Gilmorrie

The possibility of getting shreds of Teflon tape in the system is worse when the joint has to be disconnected for any reason - even if the tape was started after the first couple of threads.

Many DIYers underestimate the torque required to make up leak-free threaded connections. There was a study done, possibly by Bell & Gossett, that had a group of experienced plumbers make up threaded connections of various sizes, by "feel," but using torque wrenches to record torque for the study. The data was boiled down to tables of recommended torques - which were rather high. I checked a couple of my books, and couldn't find the information that I thought I had.

I avoid Chinese fittings like the plague.

ethicalpaul

> @Gilmorrie said:

> I avoid Chinese fittings like the plague.

How? Even my local parts counter only had Chinese brass fittings when I went there (which I often can’t due to having a day office job, so I buy a lot on Amazon)

Also, Chinese companies make like every precision part in every computer and phone, etc. They can do amazing work, but just like with US plumbing contractors (as we see here every day), not for bottom dollar.

ChrisJ

Gilmorrie said:

The possibility of getting shreds of Teflon tape in the system is worse when the joint has to be disconnected for any reason - even if the tape was started after the first couple of threads.

Many DIYers underestimate the torque required to make up leak-free threaded connections. There was a study done, possibly by Bell & Gossett, that had a group of experienced plumbers make up threaded connections of various sizes, by "feel," but using torque wrenches to record torque for the study. The data was boiled down to tables of recommended torques - which were rather high. I checked a couple of my books, and couldn't find the information that I thought I had.

I avoid Chinese fittings like the plague.

Making a proper npt joint certainly takes practice. My best description would you can feel it slowly get harder and harder to turn but the point you want to be at is just past where it goes from a gradual increase to a huge one all at once. It's a very distinct feel. The real trick is stopping around that point with your fitting aimed correctly.

I'm half asleep so hopefully that came out right.

ethicalpaul

Do the pros cut their threads in order to facilitate the part facing the correct way when at correct torque? I’m so ignorant of threads

ChrisJ

> @ethicalpaul said:
> Do the pros cut their threads in order to facilitate the part facing the correct way when at correct torque? I’m so ignorant of threads

No, but some do cut crooked threads intentionally to get piped to line up. That takes more skill than I have.

Hinman

Regarding pipe dope, will it make the fitting easy to remove in the distant future if need be the same way say Teflon tape or anti-seize does? I’ve wrenched some old old pipes and they were near impossible to remove. I’m assuming they didn’t have any pipe dope on them?? If pipe dope alone doesn’t function like an anti-seize compound I can see the benefit of using both pipe dope and Teflon tape together. I’ve seen some pipe dope with Teflon in it, does that essentially provide the same benefits that’s teflon tape does but more of an all in one with the pipe dope? I know, lots of questions about pipe dope and tape but there are so many different kinds and of various prices!

chestyp74

I use hernon drop stop 923. Triangle tube used to send it with all smart tanks for stainless connections. They do not like Teflon tape on the stainless connections. I had a panel rad that needed a left hand thread bushing installed. It was not the best fit. No matter what it leaked. Then comes hernon drop stop 923. The leak stopped when NOTHING else worked.

AMservices

I use dope and teflon together on pipe larger then 2" steel because the threads are deeper and spaced wider so it needs that extra grease to let the threads slide together.
I also use both dope and teflon on any pressurized water lines, of any size because it gives peace of mind that I've made a good connection.

I put dope before teflon because the teflon holds the dope down to the threads. A lot less gets into the pipe and a lot less time spent wiping joints.

My whole life it's been teflon then dope.
Now that I'm doing steam pipe, I'm a lot more aware of the oils I'm putting into the water, so I'm looking in The pipe to see the mess it makes.
Try dope first then teflon and you'll see what I mean.
Its good to be off the first thread with dope and not have globs.

On steam boilers, any 2" pipe or smaller is teflon only, to reduce the amount of impurities added to the water.
Dope only on probe style LWCO, air vents and pressure controls.
The probe needs a good metal to metal contact to prove the circuit.
Air vents and pressure controls only get dope for the same reason you only use dope on gas pipe.
The shreds of teflon can clog and break the small holes in these devices, as it would in a gas valve.

GroundUp

Dope before tape is an excellent way to waste days chasing leaks. The dope lubricates the threads so the tape has nothing to bind to, and pushes the tape out with the tapered threads as you tighten. If you're getting any tape or dope inside the pipe, you're applying them wrong.

AMservices

I disagree. the thread crushing together creates the seal. Fittings go together just as easy and with less mess.
If you put the tape on right doesn't back off.
Haven't had the problems you describe "chasing leaks" and teflon not binding to threads. And I screw a lot of pipe.

GroundUp

If the thread crushing together made the seal, we wouldn't need sealant would we? I didn't say the tape backs off, I said it is driven off the threads by the taper while tightening. I screw more pipe in a year than most do in a lifetime and have never seen anything good come of dope before tape unless to fill the voids between threads on 3"+ pipe, which still requires a second layer of dope for lubricant outside the tape. I'm glad it works for you, but as someone who is handed new employees on a pretty regular basis, the dope before tape guys are the most prevalent leakers. The backwards tape wrappers a close second

ChrisJ

The thread crushing together does make the seal. With NPTF connections.

However, most of us are using NPT.

AMservices

Try screwing pipe dry and see how deep it goes.
The dope and or teflon reduces the friction on the threads so they slide together far enough to make the seal, Not for filling gaps.

ChrisJ

> @AMservices said:
> Try screwing pipe dry and see how deep it goes.
> The dope and or teflon reduces the friction on the threads so they slide together far enough to make the seal, Not for filling gaps.
>

Read my post above.
Dope and tape both lubrcate and seal. Try using just oil....

AMservices

> @ChrisJ said:
> > @AMservices said:
> > Try screwing pipe dry and see how deep it goes.
> > The dope and or teflon reduces the friction on the threads so they slide together far enough to make the seal, Not for filling gaps.
> >
>
> Read my post above.
> Dope and tape both lubrcate and seal. Try using just oil....

Vegetable, canola or K.y.?

JUGHNE

OK, Chris I will ask for everyone else wondering....what is NPTF?

EBEBRATT-Ed

Whatever floats your boat. A big discussion about....not much.

You can ask 100 people who have worked in the trade "Teflon or dope", what kind of Teflon? white, monster tape or yellow tape? dope with tape, or dope without tape? Dope under the tape, on top of the tape or both? What kind of dope? What do you use on steam, on gas, on LP gas, on oil, on Hot water???

My head is spinning just writing this post. 100 people and 100 different answers.

It all comes down to personal preference and what works for you. No right answers, no wrong answers.

BTW, sometimes I use "Never Seize" for dope....so their!!!!

1Matthias

Whatever the local mom-and-pop hardware store has on sale when I buy it.... Not had an issue with leaking so far.

JUGHNE

Briefs or boxers? Ford or GM??
But always belt and suspenders!!

ChrisJ

> @JUGHNE said:
> OK, Chris I will ask for everyone else wondering....what is NPTF?

https://www.hoseassemblytips.com/what-is-the-difference-between-npt-and-nptf/

hot_rod

At Caleffi we cut a lot of NPTF thread, but the US market doesn't embrace that accurate thread Sometimes we get a load of NPTF fittings over here by mistake.

As far as pipe compounds, years ago lead paint was also used, it was a fairly permanent seal.

Currently we either "lube" the thread with tape or dope. some of the pipe dope it deals with poor thread quality.

Or "glue" the thread with Loctite or that blue Leakloc that hardens.

Reminds me of the good old days, #1 or #2 Permatex for assembling engine components

Sailah

I usually use pipe dope. But then again I'm a pipe dope

At Barnes & Jones they would use Gasoila. EVERY time I'd pick up the jug I would get that matte grey dope all over my hands and it was miserable to get off. Smeared all over everything.

I have a jug of something made by Rectorseal and I use that for plumbing.

I've been recently enamored with Loctite 567. I can't remember why I bought a tube but I have it. Has a very curious smell, not sure why that's important lol but I do like it. Anyways works really well like all Loctite products but is likely overkill for run of the mill piping jobs since it's a pricey little tube. Has Teflon in it, maybe the best of both worlds? Not messy like dope either.

https://www.amazon.com/Loctite-Temperature-Sealant-Stainless-Fittings/dp/B001OI0TN0/ref=sr_1_5?ie=UTF8&qid=1544097708&sr=8-5&keywords=loctite+567+thread+sealant

ChrisJ

I got this stuff where I work. Seems decent.

GroundUp

I love that 567 for smaller joints. It takes longer to apply but is far less messy and seems to seal better too. Permabond was my favorite for many years but I switched to the 567 about a year ago and haven't touched the Permabond since.