Natural Gas: Thread Sealant vs Thread Sealant Compound

[shooon]

Recently cut and thread 50' of 1" black steel pipe for my unit heater and in floor heat system. Began a pressure test and it won't hold pressure overnight (Started at 70 and lose about 8 PSI over 24 hours)

I am starting to wonder if I used the wrong thread sealant or if I just need to cap off the ball valves at both ends? I was told I would be fine not capping the valves since they are WOG rated.

I used TF-15 (Thread Sealant Compound) and am wondering if V2 (Multipurpose Thread sealant) would have been better? (specs below)

http://www.jetlubecanada.com/tds/TF-15.pdf

http://www.jetlubecanada.com/tds/V2.pdf

In comparison the TF-15 is supposedly better for harsher environments (temperature and vibration ranges) and does not set or tack but the V2 specifically says its good for natural gas and does dry / tack up

I've pressured it up to 70 PSI and used snoop and also tried Windex. I found a single very small leak at a coupling and tightened it. Still losing pressure and am stumped where the leak could be.

I'm thinking of gassing up the line and using a gas leak detector to help pin point the leak since the soap method isn't working for me.

 

[rlitman]

Bubbles are more sensitive than leak detectors.

WOG is a rating that comes with a pressure. But you shouldn't be leaking through the valves. In any case, that would show up with bubbles.

Did you get all the joints sufficiently tight?

 

[Milton Shaw]

I had the same type of problem and the leak was in the gauge assembly and not in the pipe during the test. Put together a couple of pieces of pipe and fittings that you can pressurize and then throw it in a bucket of water and see for sure that the gauge is not the problem.

 

[AndyCBR]

Check for leaks with a soap solution. 90% of the time the leak is mechanical (IE a joint).

We do underground petroleum equipment and the old saying goes if it doesn't hold air there is a leak, find it. Now a very large system will fluctuate with temperature changes but not much.

You can also use the soap solution to check the ball valve and handle for leaks. Yes we have had ball valves leak before.

If you're still stumped switch gauges.

Also soap the entire length of the pipe. We have had defective pipe before with pinholes in the body or seam.

Do a longer test, not just overnight to assure the pressure is steadily dropping and not temperature fluctuation.

The pressure is going somewhere.

 

[shooon]

Thanks!

Strangely enough my gauge setup developed a leak at the start of the test, even though it was perfectly fine when I used it on my in floor PEX testing(I had used the bucket method) I replaced the gauge with a more expensive liquid filled one. I am confident the gauge is good now

I have not actually placed anything inside the valves to see if they are leaking or not, I didn't think it was good to contaminate the inside of the piping. All of the shorter fittings and my swing joint were assembled on a pipe vice and are definitely good for tightness.. I'll maybe pull it apart and go over everything again + cap the valves.

Just wasn't sure if I should swap my pipe dope out for the V2 stuff since I will be going through the trouble of resealing a couple connections anyway.

Possibly part of my issue is it's -15 to -20 C here right now, so the bubble check might not be working as well since the leak stuff is a bit thicker in the cold

 

[shooon]

Also soap the entire length of the pipe. We have had defective pipe before with pinholes in the body or seam.

Good to know.

I'm leaning towards the pipe or the valve at this point!

 

[BD1]

Natural gas piping is normally tested at 10 PSI for 24 hours by local gas supplier in my area. No need to test at that high of pressure unless required.

As for testing we use Dawn dish soap and water in a spray bottle. Mix kinda soapy , spray on, and use paint brush to direct soap bubbles to joint and hub of fitting.

 

[Streetbu]

My buddy is a union pipe fitter, he was taught to use pipe dope, then wrap with tape also at every single joint. Don't know why they do that but if it works for the union guys, it works for me. He is the one that basically plumbed my shop air for me and I dont have a single leak from a joint.

 

[Firebrick43]

My buddy is a union pipe fitter, he was taught to use pipe dope, then wrap with tape also at every single joint. Don't know why they do that but if it works for the union guys, it works for me. He is the one that basically plumbed my shop air for me and I dont have a single leak from a joint.

Probably cause they don't know the business end of a pipe threader like they should or don't change their die in a timely manner. If every thing is right nothing should be needed for a leak proof joint. Since this world isn't perfect dope or tape is recommended, but both means someone is just plain sloppy.

 

[Dark Horse]

Probably cause they don't know the business end of a pipe threader like they should or don't change their die in a timely manner. If every thing is right nothing should be needed for a leak proof joint. Since this world isn't perfect dope or tape is recommended, but both means someone is just plain sloppy.

With quality domestic, euro, or Japan sourced pipe I would agree. Most suppliers are carrying lower cost pipe sourced in turkey, china, and Korea(hit or miss with this source)
The pipe is inconsistent. Some parts of the same tube cut clean, a foot later its playdo. Same for threading. A new properly set die, and you still rip threads out. Grab an old domestic piece, threads cut perfectly clean.

Quality pipe is becoming a special order item due to cost. Its only a little more $ but the suppliers get a better markup on the junk so they stock it and the uptick in die insert sales is a bonus. My sales guy admitted this to me when we returned an order of junk pipe

 

[D45]

Never ever use both tape and dope together

The thick white dope paste is the best

Are you using import black iron fittings and pipe, or American? I've seen brand new import junk leak, no matter how tight, with good pipe dope

The extra funds spent on domestic iron is well worth it

 

[Steevo]

When I plumbed the gas line into my shop, I capped the pipe run with a tee, put a low pressure gauge in the tee, and pressurized it at 10psi. In a day it was down to 5psi. I tried again, with same result. I was about to go bonkers with the fittings when I thought to try a different gauge. Turned out the first gauge was leaky, not the pipes or (doped) joints.

 

[FullRaceMerc]

I have seen leaks at the schrader fill valve at the gauge, the gauge itself, the nut at the handle of a WOG valve, through a valve, at any joint. Never in the length of pipe itself in my experience. With the exception of once always the fault of the hardware/threads, not the compound used. Some compound has a shelf life & it is important to keep an eye on the age.

I use bubbles & give them a couple of minutes to locate small leaks. If it doesn't hold pressure I check everything except the length of pipe. 10-15 psi for gas. Here where it gets pretty hot pressure will drop overnight due to contraction. During the day expansion should raise it back to the same point.

Our local gas company doesn't accept the usual overnight test with an analog gauge anymore. Its a digital gauge now that reads in thousandths of a pound. Leaks show immediately with the fancy gauge. Tests last 5 minutes. Stuff that has been is service for 50 years no longer passes.

 

[oilslick]

Why not tape and dope?

 

[AndyCBR]

Tape and dope works great for fluids that don't dissolve teflon tape. Sprinkler guys and plumbers regularly use white dope and white teflon tape together with success and this is common practice.

For those of us that plumb combustible fuel systems the tape is not an option. We only use various brands of teflon impregnated pipe dope (Gasoila is typical).

We regularly test fuel systems with 60 psi of N2 and go up to 100psi if we need to find an especially small leak. The only reason we use N2 is convenience and when testing an existing system with residual fuel in the lines we aren't making a bomb with compressed air (oxidizer).

If every thing is right nothing should be needed for a leak proof joint.

This is patently false and not sure where you are getting your info from. There are several reasons for pipe dope. Sealing, for one, and to prevent galling and lubricate the threads is probably the most important.

 

[rlitman]

Tape and dope works great for fluids that don't dissolve teflon tape...

Please tell me what dissolves teflon (that can be contained in a pipe). LMAO.

 

[AndyCBR]

Please tell me what dissolves teflon (that can be contained in a pipe). LMAO.

You are only showing your ignorance.

The body of the tape dissolves in fuels, it basically "melts" for lack of a better term. Throw a roll in a cup of gasoline and see for yourself.

I am no chemist but I don't believe the teflon itself is the problem but the binder or carrier that makes up the structure of the tape itself.

 

[Boilerhouse]

You are only showing your ignorance.

The body of the tape dissolves in fuels, it basically "melts" for lack of a better term. Throw a roll in a cup of gasoline and see for yourself.

I am no chemist but I don't believe the teflon itself is the problem but the binder or carrier that makes up the structure of the tape itself.

You are right in that white teflon is not rated for natural gas, but some teflon tapes are, I believe they are coloured yellow or light pink.

 

[Firebrick43]

This is patently false and not sure where you are getting your info from. There are several reasons for pipe dope. Sealing, for one, and to prevent galling and lubricate the threads is probably the most important.

https://en.m.wikipedia.org/wiki/National_pipe_thread

Read the first paragraph. The threads are self sealing, again as I said, if everything is perfect! I then said things rarely are and to use "either dope or tape" for sealing purposes. Also you automatically assume that dope/tape are the only lubricants? Many gas and oxygen systems use nptf threads and use no dope or tape, brass is self lubricating

Originally npt threads were not doped or taped either. They were steel or brass pipe paired with cast iron or cast bronze fittings. Cast iron and bronze are self lubricating and was some what soft to deform slightly to seal well enough for the times. Plastic npt threads need neither tape nor dope normally either for the same reason.

Also please remember, when you thread a pipe what do you use? Heavy cutting oil with lots of sulfur in it. Do you then spray the threads down with lots mek or mineral spirts to remove every last bit of oil? Or do yo just wipe it with a rag, maybe blow the chips out and then put it together? Bet the latter? Think maybe there is still some lube left on it? Even store bought steel pipe and fittings come doused in an oil for rust prevention.

Want me to continue? Or is that patently enough?

 

[AndyCBR]

https://en.m.wikipedia.org/wiki/National_pipe_thread

Read the first paragraph. The threads are self sealing, again as I said, if everything is perfect! I then said things rarely are and to use "either dope or tape" for sealing purposes. Also you automatically assume that dope/tape are the only lubricants? Many gas and oxygen systems use nptf threads and use no dope or tape, brass is self lubricating

Originally npt threads were not doped or taped either. They were steel or brass pipe paired with cast iron or cast bronze fittings. Cast iron and bronze are self lubricating and was some what soft to deform slightly to seal well enough for the times. Plastic npt threads need neither tape nor dope normally either for the same reason.

Also please remember, when you thread a pipe what do you use? Heavy cutting oil with lots of sulfur in it. Do you then spray the threads down with lots mek or mineral spirts to remove every last bit of oil? Or do yo just wipe it with a rag, maybe blow the chips out and then put it together? Bet the latter? Think maybe there is still some lube left on it? Even store bought steel pipe and fittings come doused in an oil for rust prevention.

Want me to continue? Or is that patently enough?

You can continue as long as you like but there is no substitute for pipe dope to enhance sealing and prevent galling of tapered pipe joints in modern piping systems assembled in the field.

You insinuated in your first post that dope was some type of crutch to help cobble together mismanufactured fittings put together by inept tradesman.

If you are trying to seal NPT joints without it you are foolish and uninformed.

Call us to fix your leaks when you screw together your joints without dope. It's job security.

 

[Firebrick43]

You better Go back and re read my first post.

Last sentence.

"Since this world isn't perfect dope or tape is recommended, but both means someone is just plain sloppy."

Notice how I said "dope OR tape is recommended".

Later in the sentence is, "but both means someone is just plain sloppy." This means if someone is using "both together" they are sloppy.

Let me further state for the record and be as clear as possible for you.

If you use tape on any hydraulic system or a pneumatic system with valve, checks, or flow controls you are a hack as well. Dope only.

And as for chicom/Indian ****, if it's require special orders or what should be normal quality, well that part of being a craftsman thats proud of the work they do. At work I have to personally look up part numbers and state "do not substitute". And the controller has come on to piles of parts on his desk for ordering substandard ****.

 

[matt_i]

I always use Loctite 565 PST. Have not had an issue with it in any residential or automotive application.

I would think that if perfectly gaged (both male and female) and perfectly cut tapers then sealants could probably be eliminated. But that's a pipe dream (pun intended) where the die sets float, the pipe isn't actually perfectly round, and a low quality of metal that sometimes tears instead of cuts.

For those actual common field conditions, I'd rather trust a lubricant to allow more of the wrench torque to be transferred into seating the tapers rather than trying to pushing a "snowball" of torn/galled metal thru the threadform. The fully seated tapers is what makes the joint pressure tight, not the ability of the "sealant" to clog up deformities in the threadform.

Its correct that the metal-to-metal contact is what seals the joint, but the galling that can occur in a joint...they do get warm when properly done...will lead to the aforementioned metal "snowballs" that create easy leak paths. Lube the threadform and avoid the snowballs.

 

[Jackfre]

Probably cause they don't know the business end of a pipe threader like they should or don't change their die in a timely manner. If every thing is right nothing should be needed for a leak proof joint. Since this world isn't perfect dope or tape is recommended, but both means someone is just plain sloppy.

If you look at the threads cut on pipe dies you will see it is a tapered thread. The actual joint is "made" by metal to metal contact. The purpose of pipe dope is not to provide the seal but to lubricate the joint so you can get deeper into the threads. Pipe dope is not a sealant. Try putting a joint together without pipe dope and see how far you can get. You won't make two turns with properly cut threads. It is true that pipe today is inconsistent. You will run into hard spots that will tear threads off. Good sharp dies are imperative...and pricey. I was taught that tape is not good on gas lines. The reason being that when a taped joint is assembled the tape is cut into threads. If you cover the first thread on the pipe with tape you can have a floating piece of teflon that can potentially move to the gas valve, creating problems. I have never seen it in 54 years of doing it, but that is what I was taught and it makes sense to me. I am perfectly comfortable with with the original yellow Rectorseal on gas.

To the OP, look for sand holes in fittings in your soap tests. They happen and just as the pipe has problems, so too do the fittings. You should do your test at 10#.

 

[matt_i]

Also wanted to add that whenever I do a gasline pipe job, I order fittings from McMaster Carr because despite not advertising this, you get Ward Mfg fittings which are made in USA and of a clearly higher quality casting and machining than the junk sold at Big Box. I haven't figured out a way to get higher quality pipe locally though....

 

[Smoker]

For what its worth my inspector told me both tape and dope are acceptable for gas service but he's seen less issues during pressure tests when dope is used. So that's what I went with.

In my professional life I've used teflon tape in an industrial setting and pressure tested it successfully to 2600 psi. And yes there's a chemical solvent that indeed dissolves teflon, no it isn't gasoline.

 

[AndyCBR]

I'll disagree that dope does not offer sealing properties. Minute leak paths are sealed that cannot be sealed by imperfect (99.99999% of joints) sealing of the joint taper. Whether it is galling, dull threads, tearing of the metal, lack of squareness of the cut end prior to threading, out of round conditions, or any other manner of real world imperfection of the tapered joint fit, the dope plugs up the minute spaces that allow leaks to pass through the threaded joint.

 

[D45]

Home Depot, Lowes, and Menards only carry Mexico and China made black pipe and fittings

Most True Value stores also carry China and Mexico made black pipe/fittings

I found a smaller True Value near me, that only carries Anvil brand, which is USA

It definitely is more expensive but well worth it

There are two kinds of pipe dope around here, thick white paste and a grey running gel

I only trust and use the thick white paste

 

[HoosierBuddy]

So...I buy pipe dope by the case and threaded fittings by the truckload, if that makes me any sort of "expert".

Here's my take on it:

Thread sealants, such as Retroseal 5 (aka "Pipe Dope") provide both lubricity and sealing properties to threaded joints. http://www.rectorseal.com/rectorseal-no-5/

It is specifically called "Thread Sealant" by the manufacturer.

If you look at the specs for any NPT thread, the dimensions are given out to the ten-thousandth of an inch. Without extremely sophisticated measuring instruments, I don't know how you could possibly measure to even know if a thread is made properly, although if you can visibly see any imperfection than it OBVIOUSLY isn't to spec.

A methane molecule is about 4 angstroms in diameter...which is 0.0000000016 inches. If there is a path through the threads that size or bigger...the joint can leak natural gas. A water molecule is even smaller. SO...asking threaded joint, with no sealant, to seal seems to be asking a bit much.

My experience, above and beyond the theory, is that a good thread sealant is a vital part of any successfully assembled threaded joint. I have used tape myself in the past, but personally have had less luck with it. It makes a cleaner joint and is less messy overall, but is harder to get to seal properly in my experience. I prefer a good pipe dope.

So...the differences in thread sealants, in my experience, is not really how they do initially, because they all work pretty well right out of the tube or can. The issue is how fast they dry out and will leaks develop years down the road. Also, some sealants can set up so hard that they make joints very difficult to disassemble for maintenance purposes.

The rectorseal 5 I'm using was a switch I made about 5 years ago and is working well to this point...but I've got literally 10's of thousands of threaded joints to maintain...so if it starts failing at 10 years...I'll have a bunch of work to do.

Phil

 

[Jackfre]

Ok, yes you get some sealing quality from pipe dope, but it is incidental to the mechanical seal of the threads themselves. I've always looked at the "Sealant" part of the label as the contribution of the Marketing Dept.

 

[shooon]

Thank you very much for all the advice and information everyone.
The temperature warmed up to -5, I used hot soapy water and went over everything again and found the culprit!

There was a brass ball valve that was leaking at the threads. I am thinking I didn't find it the first time because it was too cold for the soap to work and it would just freeze right away. I took it apart, brake cleaned, dried, and resealed it 2x but it still kept leaking!! Tightening made it worse. I replaced the valve since the threads on the pipe looked perfect and it has fixed the leak. Must have been an issue with the threads when the valve was manufactured I am thinking.

--------------------------------------

I did some research on dope vs tape and dope and tape combined.
typically dope manufacturers do not recommend using tape and dope together because it 'may' overload the threads. The gas inspector assigned to inspect my work actually prefers to use both himself, so I guess to each his own.

I found a good video on youtube taken from here that shows a closeup of how NPT threads mate together and what is needed to form a good seal. I've attached a couple pictures too.

 

[rlitman]

Thank you very much for all the advice and information everyone.
The temperature warmed up to -5, I used hot soapy water and went over everything again and found the culprit!

There was a brass ball valve that was leaking at the threads. I am thinking I didn't find it the first time because it was too cold for the soap to work and it would just freeze right away. I took it apart, brake cleaned, dried, and resealed it 2x but it still kept leaking!! Tightening made it worse. I replaced the valve since the threads on the pipe looked perfect and it has fixed the leak. Must have been an issue with the threads when the valve was manufactured I am thinking.

--------------------------------------

I did some research on dope vs tape and dope and tape combined.
typically dope manufacturers do not recommend using tape and dope together because it 'may' overload the threads. The gas inspector assigned to inspect my work actually prefers to use both himself, so I guess to each his own.

I found a good video on youtube taken from here that shows a closeup of how NPT threads mate together and what is needed to form a good seal. I've attached a couple pictures too.

This thread is full of SO much misinformation, that I really feel sorry for you, but clearly you stayed on the right track.

Brass female parts will often do what you described. They like to crack if overtightened with a steel male tapered thread (due to hoop stress). The same thing happens when you screw a metal male tapered thread into PVC. The crack will be damn near invisible, but this is exactly why you pressure test and test with bubbles. GOOD WORK finding it! We're all glad you didn't pressurize your system without testing it first.

Or sometimes there's a hidden crack left behind from the time it was manufactured.

As for tape vs dope, no amount of soft-setting dope alone will overload an NPT fitting (it just squishes out), whereas too much tape, or tape plus dope can. In NTP fittings involving iron, steel or brass, tape is in most regards inferior to dope. But that does not mean that there is never a call for tape+dope. I find that to be helpful with sweated copper NPT connections.

As for NPT sealing, I've said this before, and your video makes it clear too, NPT has a helical leak path that will not seal without a sealing material in there. How much material is needed depends on both the quality of the materials, as well as the relative strengths of the male vs female threads, as thread deformation will take up some, but not all of the space, but with dissimilar materials involved, the deformation will not be symmetric.

NPTF (which is distinctly different from NPT) is a thread designation that is designed to seal dry, but it does not allow for a ferrous-ferrous fitting. One side at least must be brass. In any case, NPTF is not used in plumbing fittings.

 

[engineer2]

A relative worked for the gas company and he said the trick is to put pipe dope on both the male AND the female threads.

I think someone already mentioned that the Chinese pipe sold at the big box stores is of ****** quality.

 

[rlitman]

A relative worked for the gas company and he said the trick is to put pipe dope on both the male AND the female threads.

I think someone already mentioned that the Chinese pipe sold at the big box stores is of ****** quality.

For the most part, dope on the female threads just pushes a messy ring of dope into the pipe. It's not helpful at all.

My local gas company doesn't like dope at all. They prefer the crayons. I actually like the teflon crayons a lot, as nothing else is useful on the mating surfaces of a union, but that's another story. I still use Rectorseal 5 on my gas pipes.

 

[HoosierBuddy]

For the most part, dope on the female threads just pushes a messy ring of dope into the pipe. It's not helpful at all.

My local gas company doesn't like dope at all. They prefer the crayons. I actually like the teflon crayons a lot, as nothing else is useful on the mating surfaces of a union, but that's another story. I still use Rectorseal 5 on my gas pipes.

But...if you read the directions on the can? Some of the ones I've read (hope I don't lose my man card for reading the directions!)... say for best results, apply to both fittings, allow to tack and then assemble. Yes I realize no one does it that way in industry...but that's what they say to do. Rectorseal 5 for instance says to apply to both sides on larger pipe sizes. I believe LeakLok specifies it for all threads...but it's been a few years since I've read that one. In case anybody wonders why I know WAY too much about this topic...I've teach a training session on it occasionally to natural gas service techs.

Phil

 

[rlitman]

But...if you read the directions on the can? Some of the ones I've read (hope I don't lose my man card for reading the directions!)... say for best results, apply to both fittings, allow to tack and then assemble. Yes I realize no one does it that way in industry...but that's what they say to do. Rectorseal 5 for instance says to apply to both sides on larger pipe sizes. I believe LeakLok specifies it for all threads...but it's been a few years since I've read that one. In case anybody wonders why I know WAY too much about this topic...I've teach a training session on it occasionally to natural gas service techs.

Phil

I did say "for the most part".

You are correct, but yes, this is only for larger sizes. IIRC 2-1/2" and up (don't have a can in front of me...). And yes, it is important that the dope used be rated for the pipe sizes in use.

 

[AndyCBR]

Glad you found and fixed your leak!


Sent from my iPhone using Tapatalk

 

[maintguy]

Home Depot, Lowes, and Menards only carry Mexico and China made black pipe and fittings

Most True Value stores also carry China and Mexico made black pipe/fittings

I found a smaller True Value near me, that only carries Anvil brand, which is USA

It definitely is more expensive but well worth it

There are two kinds of pipe dope around here, thick white paste and a grey running gel

I only trust and use the thick white pastebout in

where about in Indiana are you located?

what about rectorseal no.5, great blue. etc?

 

[csp]

There are a number of quality pipe dopes, the white paste posted isn't the only thing that works. The person that posted that photo has minimum experience running gas line and probably has never tried anything else. Take the opinion with a grain of salt.

Rectorseal No. 5 is very good pipe dope. Every plumbing supply house I've been in has it on the shelf.

 

[rlitman]

There are a number of quality pipe dopes, the white paste posted isn't the only thing that works. The person that posted that photo has minimum experience running gas line and probably has never tried anything else. Take the opinion with a grain of salt.

Rectorseal No. 5 is very good pipe dope. Every plumbing supply house I've been in has it on the shelf.

Yes, most every plumbing supply has it, but it's hard to find in the box stores, and hardware stores are hit or miss.

That white goop from Hercules is ok.

I would just suggest avoiding any of the blue materials that harden.

 

[csp]

Yes, most every plumbing supply has it, but it's hard to find in the box stores, and hardware stores are hit or miss.

That could be, I wouldn't know about what the big box stores have. My unstated point was if it's in the supply houses, the pros use it.