Pipe Dope PLUS Teflon?

BinDerSmokDat

The instructions on my new oil tank say to apply a fuel-compatible pipe sealant to the male threads of the tank valve and THEN apply fuel safe Teflon tape over the pipe dope and then install the valve , tightening to 1.5 turns past hand tight.

Is this right? Pipe dope AND Teflon? I always thought it was a "one or the other thing, never both" thing.

Ironman

Both, but we always tape first.

HomerJSmith

Ironman, I can see you are a belt and suspenders man.

JohnNY

My guys all do both and it drives me crazy. It is one or the other. They are lubricants. That's all. When I took my licensing exam we assembled about 30 fittings and nipples to make an 8-side figure all with no dope or tape of any kind. Then we pumped 100 PSI of air into the assembly and put it under water. No leaks. The threads do the sealing. The stuff you put on the threads are simply lubricants. Of course, there are exceptions. Some compounds cure to become sealants. But that's not plumbing.

CBRob

> @JohnNY said:
> My guys all do both and it drives me crazy. It is one or the other. They are lubricants. That's all. When I took my licensing exam we assembled about 30 fittings and nipples to make an 8-side figure all with no dope or tape of any kind. Then we pumped 100 PSI of air into the assembly and put it under water. No leaks. The threads do the sealing. The stuff you put on the threads are simply lubricants. Of course, there are exceptions. Some compounds cure to become sealants. But that's not plumbing.

I'm no plumber, but watched a episode of coffee with calliefi yesterday that said sealant was needed with NPT threads.

Said that they don't actually seal on their own.

ChrisJ

CBRob said:

> @JohnNY said:

> My guys all do both and it drives me crazy. It is one or the other. They are lubricants. That's all. When I took my licensing exam we assembled about 30 fittings and nipples to make an 8-side figure all with no dope or tape of any kind. Then we pumped 100 PSI of air into the assembly and put it under water. No leaks. The threads do the sealing. The stuff you put on the threads are simply lubricants. Of course, there are exceptions. Some compounds cure to become sealants. But that's not plumbing.



I'm no plumber, but watched a episode of coffee with calliefi yesterday that said sealant was needed with NPT threads.



Said that they don't actually seal on their own.

As far as I know, this is correct.
I've successfully sealed NPT threads at 3000 PSI using tape and dope.

CBRob

At the 19 minute mark in this video.
https://youtu.be/SCe6VVw-044

ChrisJ

@CBRob

In @JohnNY 's defense, I've read many documents that claim both things.

Some claim NPT threads deform to seal and dope is primarily a lubricant.

Others claim you need it to seal the roof of the thread.

Which is correct? I have no clue.
I've found really good cut threads need very little to seal but some cheap fitting and nipples from China need dope and tape.

pecmsg

> @JohnNY said:
> My guys all do both and it drives me crazy. It is one or the other. They are lubricants. That's all. When I took my licensing exam we assembled about 30 fittings and nipples to make an 8-side figure all with no dope or tape of any kind. Then we pumped 100 PSI of air into the assembly and put it under water. No leaks. The threads do the sealing. The stuff you put on the threads are simply lubricants. Of course, there are exceptions. Some compounds cure to become sealants. But that's not plumbing.

Was true in the past just like 2 threads exposed minimum, unfortunately with the lack of quality control even with American made pipe and fittings Teflon or dope are needed.

GroundUp

With a perfect thread on both sides, in theory it should seal itself when tightened. 99% of threads are not perfect, and need some sort of sealant. Small visible threads I'll use just tape to keep it clean, gas piping I use just dope as pressure is low and it's code here, but any other water or steam piping gets both. 4-6 wraps of tape first (pulled tight, stretched deep into the threads) with a thin layer of dope over the top. No matter the method, there will be the occasional leak but I can say the possibility is much lower when using both tape and dope

SlamDunk

Our fire sprinkler installers use dope first then tape. Keeps them from getting dope all over everything.

GroundUp

What I've found with the "dope under tape" joints, is that the dope lubricates between the tape and threads which ends up pushing the tape out of the joint as you tighten, making it useless.

Intplm.

Was never taught that dope in the paste style or tape style was a lubricant. It was and is considered a thread sealant, ( for lack of a better description. )
It is meant to seal the imperfections on pipe threads. It certainly does lubricate to make things easier to screw together.
Over time, as little as overnight, leaks will surely be there without pipe dope or teflon tape.

Who here would dare install something without using one or the other.

I have found this to be a installers personal preference.
So, @BinDerSmokDat to answer your question. Either one is fine. Teflon tape is nice because it is not as messy as canned pipe dope. Teflon tape needs to be put on the threads clockwise. Six wraps for the white stuff, three wraps for the blue monster.
(Hold the fitting in your left hand and apply tape to the male threads in a clockwise, away from you, motion.) Pipe dope? apply with the brush provided.
You do not need both.

Unless the threads came from china a few years back.🙄

HomerJSmith

You're not going to pass an inspection without a sealant.

Isn't this like the age old quandary, "How many angels can dance on the head of a pin."

SlamDunk

GroundUp said:

What I've found with the "dope under tape" joints, is that the dope lubricates between the tape and threads which ends up pushing the tape out of the joint as you tighten, making it useless.

Not useless. Just proof that @JohnNY is correct.

This stuff is lubrication. Metal on metal threads chip and gall. They don't tighten smoothly, you can feel it. It also helps to loosen fittings during demo years later.

I have thousands of sprinkler heads and have yet to see one leak. Whether one or both is used is up to the pipe fitter.

What annoys me are the fittings screwed together by apes. If you are a 300 pound person bouncing at the end of a four foot wrench to tighten a fitting, you're doing something wrong!

pecmsg

https://forum.heatinghelp.com/discussion/99767/lamp-wick-for-sealing-threads

Ironman

Pipe fittings, even American ones, are not made with tolerances they once were. The Asian ones can have extremely loose tolerances.

For about the last 20 years, what's been available is junk compared to what we once had. I've had some that were so out of round that they required wicking + 12 wraps of tape + Teflon paste.

Things aren't like they were when many of us started in the trade 30 or 40+ years ago. Quality has been sacrificed on the altar of profit.

JUGHNE

Old guy told me that plumbers used to carry galv pipe nipples and fittings in the back of their uncovered open truck box.
He said the rust on the threads helped seal the fittings, they still used the pipe dope pencil stick. Rubbing across the threads perpendicularly. FWIW

In my mind it seems the tape seals the wells of the nipple threads and then the dope on top of tape would lube and seal the female threads as it was screwed in. IMO

HomerJSmith

Well, I guess I'm a belt & suspenders man. Yesterday, belt & suspenders didn't hold up my pants.

I had installed 2 Runtal towel bars. I used Teflon tape and Hercules Block. Both towel bars leaked. I took one of them off the wall and redid the Teflon tape and Block routine and remounted it. It leaked. Close examination of the threads revealed that the threads were rough and not cleanly cut. What to do? My next fix has got to be right. I could use JB Weld, Locktite or another sealing product. I have decided to use Locktite 565 and see if that works. I hate doing the job three times.

Lacquer thinner works real good at removing Block, also Automotive brake cleaner.

ChrisJ

JUGHNE said:

Old guy told me that plumbers used to carry galv pipe nipples and fittings in the back of their uncovered open truck box.
He said the rust on the threads helped seal the fittings, they still used the pipe dope pencil stick. Rubbing across the threads perpendicularly. FWIW

In my mind it seems the tape seals the wells of the nipple threads and then the dope on top of tape would lube and seal the female threads as it was screwed in. IMO

People say a lot of things.
Doesn't mean they're true unfortunately.

So now dope is a lubricant, but we're going to try and get those threads nice and rusty. Because rusty threads are known to work nice and smooth and turn together easily?

I don't know.....

JUGHNE

This rust info was collected from one of the local historians who was visiting with me as I worked on the beer coolers in the bar

He was actually pretty sharp..... Korean Vet...he had had a psycho evaluation done and came out clean.
So when people accused him of being crazy he would reply:
"I got papers proving I'm not......where are yours?"

ChrisJ

JUGHNE said:

This rust info was collected from one of the local historians who was visiting with me as I worked on the beer coolers in the bar

He was actually pretty sharp..... Korean Vet...he had had a psycho evaluation done and came out clean.
So when people accused him of being crazy he would reply:
"I got papers proving I'm not......where are yours?"

Fair enough.
Still, do you agree or disagree with what I said?

Typically when you want a bolt to torque down well you don't want it rusty. Do you?

JUGHNE

Torque on a bolt and thread sealing are not the same IMO.
I believe the theory was that the fine rust developed would act as a sealant for the threads filling any gaps. I am not talking of major rust beyond recognition, just fine layer.
The pipe dope of the day did little to provide lubricant.
Also, these were threads of good steel from the 50-60's.
And because of lack of lube they were wrenched tight as hell by gorillas.

I am not recommending the rust sealant process, just throwing out the Urban Legend.

I will wire brush any rust off nipples and inside fittings as possible and think of old Jack every time......he did live with his mother BTW whom I never did see.

These dope/tape discussions show up frequently and I learn a lot from them. For instance had never heard of wicking before this.
Took something apart years ago and it had string in it for a lav compression fitting and wondered what was up with that. Later found out here it was common.

SlamDunk

What's the rule for wet torque vs dry torque again?

Ron Jr._3

I hate to disagree with some of my colleagues here , but thread sealant is not just a lubricant.

If it were , why aren't we all using waste oil , vegetable oil or even dish soap or butter on threads ?

I've been using both Teflon and a spread-on sealant on anything threaded for water and steam all my working career. I've come to find if you just use one or the other you'll have a leak eventually. Not all the time. Maybe 1 in 30 joints. But that's enough for me !

Getting back to the original post , I dont know of any Telflon based product thats recommended for oil ? I double-seal everything oil based. Meaning I spread the sealant on every inner and outer thread. From 2 inch down to 1/4 inch.

SeanBeans

The only things I use only dope-only on is gas pipe and LWCO probes.

Everything else is tape and dope.

Ironman

HomerJSmith said:

Well, I guess I'm a belt & suspenders man. Yesterday, belt & suspenders didn't hold up my pants.

I had installed 2 Runtal towel bars. I used Teflon tape and Hercules Block. Both towel bars leaked. I took one of them off the wall and redid the Teflon tape and Block routine and remounted it. It leaked. Close examination of the threads revealed that the threads were rough and not cleanly cut. What to do? My next fix has got to be right. I could use JB Weld, Locktite or another sealing product. I have decided to use Locktite 565 and see if that works. I hate doing the job three times.

Lacquer thinner works real good at removing Block, also Automotive brake cleaner.

Homer, you need to use wicking followed by about 10 wraps of Teflon plus Block.

You can make wicking from Teflon tape by taking 18" long pieces and stretching them out and twisting them tight into long strings.

ch4man

found this while searching for a special orifice to restore an old obsolete space heater..
fwiw

All pipe thread types used in plumbing are specified by the American National Standard for
pipe as accredited by the American National Standards Institute (ANSI).
National Pipe Threads (NPT) have tapered threads. These are the most common threads
used for general purposes. NPT threads are designed with a 60 degree thread angle, and
are used for joining and sealing pipe to fittings in low pressure air or liquids and also
mechanical applications. The tapered thread is 3/4" over one foot of length. Tapered
threads are deeper at the end of the pipe and are increasingly shallower the further they are
from the end of the pipe. The taper on the pipe only allows the pipe to screw inside the
fitting until it is forced to stop because of the taper. The distance the pipe can be screwed
into the fitting is specified by the ANSI standard. After tightening with a wrench the threads
may have slight spaces between the pipe and fitting which could cause a leak so a pipe
sealant must be used to ensure any gaps are filled.
The Dry-seal thread (NPTF) also have tapered threads. NPTF threads are used when the
application is such that pipe sealing compounds may fail due to higher heat or pressure than
normal NPT threads can withstand. The threads are designed to seal mechanically by
slightly, but sufficiently, crushing the threads when tightened with a wrench. This allows for
joining the pipe and fitting without sealants.
The NPT and NPTF threads are interchangeable with sealants such as PTFE tape or suitable
pipe joint compounds. None of the other thread standards are interchangeable. Female NPT
threads can be designated as "FPT" and male NPT threads can be designated as "MPT."

HomerJSmith

Thanks, Ironman. The Locktite 565 failed. There was a significant reduction of leakage, but leakage, never the less.

I'm going with JB Weld. Gad!

BinDerSmokDat

Thanks for all of the feedback everyone.

I already bought some Blue Monster pipe dope and decided to also get blue teflon tape. I had plenty of the white stuff, but decided that for $4 it was worth it. I will do both, as recommended. I'm only using it on the tank valve and the NPT end of some flare fittings for the OSV and new Firomatic. 5 NPT joints total.

Also I figure that the blue teflon can't be any different from the stuff I already have, I've heard it is just thicker, but again, for $4 a roll it's cheap good mojo. I've used plain old white plumbing tape on everything from liquid CO2 for paintball guns, to gasoline for carb fittings, to fittings for my solvent parts washer. It's never failed.

Interestingly enough, I have de-commissioned the at-least-20 yr old tank and when I removed the old valve, the threads were bare, no trace of any sealant at all, dope or tape. The brass threads of the valve were clean and shiny where they engaged with the tank.
(Incidentally I'm not reusing the old Firomatic OTV, I just wanted to install a 1/2" plug since the valve is seized open.)

BinDerSmokDat

On the rust topic,I have a fun fact for you...
The bike I'm on in my profile pic is a Ural, a Russian motorcycle. The metallurgy of some parts is pretty questionable, which led to people referring to rust on nuts and bolts as "Russian Loc-tite."

The rule is if it is an exposed bolt and you only want it to come off when the part is being replaced, use Loc-tite.
If you NEVER want the bolt to come off, leave it alone, the Russian Loc-tite will do the rest.

gdowie

I read the same tag when installing my new oil tank. Read a bunch of rants online about tape vs. dope... Proceeded to install with dope first, then tape on top for all joints in my new boiler install. I've little experience to draw on, but 2 months in and zero leaks.

https://forum.heatinghelp.com/discussion/171601/diy-heating-upgrades#latest

ch4man

the dope then tape or tape then dope is the silliest debate ive ever heard.
think about it. the peaks of the threads grind into the valleys of the other threads. period. one side is dope, the other tape. the threads valleys and peaks dont know or care which one is what gender (male or female). i should add i dont mean to suggest one try to to tape/dope the female threads, we all know to keep the junk outta the inside, not just the fact of it would be pretty tough to apply tape to a female fitting!
to keep from making a mess and nothing more should i chose to use both, itll be tape first

ChrisJ

ch4man said:

the dope then tape or tape then dope is the silliest debate ive ever heard.
think about it. the peaks of the threads grind into the valleys of the other threads. period. one side is dope, the other tape. the threads valleys and peaks dont know or care which one is what gender (male or female).

to keep from making a mess and nothing more should i chose to use both, itll be tape first

Out of everything on the internet, you feel this is the silliest debate?

Really?

Should I give you some links to Flat Earth discussions?

ch4man

over 3 decades of being in the business. internet was not used for that. using independent thought to figure things out is becoming a rare skill

what do you got?

ChrisJ

ch4man said:

over 3 decades of being in the business. internet was not used for that. using independent thought to figure things out is becoming a rare skill

what do you got?

Here you go.
This is what happens when some people use independent thought.

https://wiki.tfes.org/Flat_Earth_-_Frequently_Asked_Questions


I've got a headache now.

SlamDunk

That's not an example of independent thought. It's more an example of how contagious ignorance is.

ratio

Ohhh… I so want to follow that link; but I'm not sure I'm up to it.

ChrisJ

SlamDunk said:

That's not an example of independent thought. It's more an example of how contagious ignorance is.

Oh no, someone came up with that and they were certainly thinking independently.

ratio said:

Ohhh… I so want to follow that link; but I'm not sure I'm up to it.

Every time I've read this stuff it literally makes me ill for a while.
Be careful.

SlamDunk

My co-worker's daughter dated a flat earther. It frustrated him to no end. The kid an answer for everything. Listening to my co-worker talk about this young man reminded me of that grade school kid who was always obnoxious just to get attention.

I want to ask a flat earther why, if the world is flat and before GPS, did sea and air vessels require hyperbolic navigation aids? Line of sight should work perfectly in a flat world -especially at altitude!

Why can't we build large enough transmitters so the North and South poles can communicate directly?

EdTheHeaterMan

Fuel oil lines and teflon tape is a NO NO ! ! ! This is from the Suntec instruction sheet:
"GENERAL INFORMATION • ALL SYSTEMS
IMPORTANT INFORMATION Long or oversized inlet lines may require the pump to operate dry during initial bleeding period. In such cases, the priming may be assisted by injecting fuel oil into the pump gearset. Under lift conditions, oil lines and fittings must be air tight. To assure this, “pipe dope” may be applied to both the used and unused inlet and both return fittings. DO NOT USE TEFLON TAPE!! DO NOT USE COMPRESSION FITTINGS!!"