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When to use PTFE Teflon Yellow or White tapes or Pipe Dope

January 17 by kevin 23 Comments

allthumbsdiy-images-pipe-sealant-4-v2-fl

The purpose of thread sealant tape (a.k.a. “Teflon tape”) or pipe dope is threefold:

  • First, the lubricant qualities allow male threaded pipe to be turned deeper into female threaded fittings to prevent leaks;
  • Second, it acts as a filler to smooth out micro abrasions or surface irregularities on threads;
  • Third, it keeps the male and female threads from rusting together (a.k.a. seizing);
There were lots of comments about the earlier photo that showed sealant tape wrapped in the wrong direction (thank you for pointing out my oversight). I have since replaced the stock photo with my own and wrote a post titled, How To Correctly Apply Teflon Tape to a Thread for your reference 🙂

PIPE THREAD TYPES

allthumbsdiy-plumbing-ptfe-an-thread-flAN thread is a type of fitting used to connect flexible hoses and rigid metal tubing that carry fluid (it stems from a joint standard by the U.S. Army and U.S. Navy, hence “AN”).

AN thread provides a positive seal that should seal correctly with specified torque torque range with no leaks. The AN should not require a thread sealant.

allthumbsdiy-plumbing-ptfe-npt-thread-flNational Pipe Thread (NPT) taper is a U.S. standard for tapered threads used on threaded pipes and fittings.

In contrast to straight threads that are found on a bolt, a tapered thread will pull pipes and fittings tight together, providing effective seal for pipes transporting liquids, gases, steam and other fluids.

Although SAE and ASTM (organizations that set U.S. industry standards) set very precise thread class specifications, many threaded products carried by large box retailers have varying degrees of deviations from set specifications (i.e. micro surface imperfections like chatter or spalling), thus requiring a use of thread sealants.

USE SETTINGS

In a residential home environment, we are primarily transporting non-caustic substances like water, natural gas, Liquified Petroleum Gas (LPG), fuel oil (and maybe compressed air and oxygen).

Although there is no hard and fast rule, we can broadly categorize residential threaded joints as either permanent or semi-permanent joints to identify appropriate applications for thread sealants:

Joint Type Description Product Suggestion
Permanent Joints Any joints which would normally be installed during the rough-in or stack-out phase of the plumbing and which could be reasonably expected to last the lifetime of the structure. These would include galvanized iron water lines, threaded connections on main & zone valves on the water distribution system and gas lines. Pipe Dope
Semi-permanent Joints Any joints which we typically make during the final trim out phase such as fixture angle stops, shower arms, shower heads, tub spout to the stub outs or any joint which we could reasonably expect may be changed periodically for general maintenance or aesthetics purposes during the life of the structure. Sealant Tape

PTFE THREAD SEALANT TAPES

When a thread seal tape was first introduced, it only came in a single density type (“white Teflon tape(1)“) that was commonly found in large home improvement stores. Later they began making a double density version, which was twice as thick in the same color (unfortunately with the same “white” color).

(1)Teflon tape is used ubiquitously when referring to a thread sealant tape. However, the word “Teflon” is a trademark name owned by Dupont Chemical Corp. Although Dupont no longer manufacturers Teflon tapes, it still enforces its trademark rights. That is why you see other manufacturers like Oatey refers to it as PTFE (PolyTetraFluoroEthylene) thread sealant tapes.

One very important thing to remember is that PTFE thread sealant tapes and pipe joint compounds are only to be used on NPT male threads. Neither should be used on SAE mechanical threads or as a gasket sealer (i.e. sink basket gasket).

PTFE THREAD SEALANT TAPE COLORS

Since many state and local codes adopted the use of double density tapes when making connections for natural gas, the use of same color for two different thickness presented a challenge when time came to inspect a job. Thus, a “yellow TEFLON tape” was later introduced for such application.

Since then, ASTM has broadened the specifications for PTFE tape colors:

Tape Color Description Example/th>
White single or double density, should only be used on NPT threads up to 3/8 inch in diameter LASCO White 1/2-Inch Double Density PTFE Thread Seal Tape
Yellow double density, often labeled as “gas tape” Oatey Yellow 1/2-Inch Gas PTFE Thread Seal Tape
Pink triple density, required on all joints 1/2″ or larger LASCO Pink 1/2-Inch High Density PTFE Thread Seal Tape
Green Oil Free PTFE tape, required for use on all lines carrying oxygen (i.e. – medical oxygen or welding oxygen lines) Gasoila, 1/2-Inch Green PTFE High Density Thread Tape, 3.7 mil Thick

PIPE DOPE / LIQUID THREAD SEALANT

Pipe dope, technically known as pipe joint compound is both a thread lubricant and thread sealing compound. Unlike a thread sealant tape, pipe dope is designed to make a pipe thread joint leak proof and pressure tight by brushing on a pasty substance to a male thread (never to a female thread because some of it will push into the pipe.

Some people use pipe dope on top of thread sealant tape but many manufacturers say there is no added benefit to that setup.

Pipe dope itself can be classified into 2 distinct categories:

Pipe-Dope Type Description Example
Oil Based Usually comes in a dark gray paste designed to work on all metal based pipes and fittings Oatey Pro Dope
Non-Oil Based Usually comes in a white paste that works with all metal and PVC-based pipes (make sure to read the product label to verify that a given product can be applied to PVC/cPVC threads such as P-traps, tailpieces, waste & overflow, etc.) Rectorseal Pipe Thread Sealant

While there are number of pipe dope product on the market, the one that seems to be most widely accepted by plumbers, pipe fitters, HVAC techs and electricians is products from RectorSeal.

Rector Seal #5 is applicable to metal and PVC; Rector Seal #7 is only applicable to metal. Rector Seal has a comprehensive thread sealant product matrix (external link to RectorSeal.com)

If the thread you are working on will be exposed to extreme temperatures, a better suited product might be a liquid thread sealant called Permatex Thread Sealant with PTFE. This product has the same sealing capabilities but it is also designed to work in a broader range of temperatures (-60 to 300 F).

TIPS TO REMEMBER

  • The main purpose of a thread seal tape / liquid thread sealant is to seal out micro abrasions or surface irregularities on threads. If you have a major gash or nick on a thread, you will need to replace the pipe section or re-thread it, rather than applying a thicker seal tape layer;
  • Applying more than 3 layers of sealant tape is not recommended;
  • When starting out, make sure the seal tape is not covering the pipe opening. Any exposed seal tape may break loose over a period of time and cause a blockage problem; in the future;
  • Pipe connections generally turn clock-wise but there are instances when that is not true (i.e. gas pipe union joint). Always test out and make a note of the pipe rotation before applying the tape and remember that the tape application must “go with the flow”;
  • You cannot connect dis-similar pipes together (i.e. copper-to-steel) and hope that a thread sealant tape will prevent from interacting with each other, possibly causing corrosion problems. In this situation, you must use a dielectric union (something like this)
  • If you need a gasket sealer, you may want to checkout can use hyolomar based products like Valco Cincinnati Hylomar Compound or Permatex Oil Resistance RTV Silicone Gasket.

Final Thoughts

So what do I use in my plumbing projects?

I tend to apply both the sealant tape and pipe dope if there is plenty of space around the pipe I am working on or if I am working with black steel pipes (generally used for natural gas) because their threads tend to be rougher.

If the working space is tight (let’s say a 1/2″ water pipe straddling a floor joist), I tend to go just with pipe dope. I only use sealant tapes for drink water supply lines (i.e. kitchen sink).

If you have some time, head on over to the post titled, How To Correctly Apply Teflon Tape to a Thread to see more examples.

Well, I hope you found my post on pipe thread sealants to be useful and signup for my free newsletter. The sign up form is found on the upper right screen and I promise it will be spam free.

Thanks again for reading my post and good luck with your DIY project!

 

Filed Under: Plumbing Tagged With: compare thread sealant methods, compare thread sealant tapes, non-oil based pipe dope, oatey, oatey pipe dope, oil-based pipe dope, Pipe Dope Teflon Tape, ptfe tape, rector seal, rector seal pipe dope, teflon tape, teflon tape vs pipe dope, teflon thread sealant tape, thread sealant liquid pipe dope, thread sealant tape

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Reader Interactions

Comments

  1. Faz says

    November 5 at 4:13 pm

    Great Article, thanks for the data.

    For the average DYI’er tho, that top picture is a bit misleading, as:
    1. It’s usually easier to apply the tape under tension with the roll reversed from what is shown, and
    2. That pipe in the picture would have to be left handed thread if the tape was applied as shown – which is not common and only used in some gas fittings – which would also mean that it should probably be yellow tape.

    Obviously a stock photo of some kind, but again, a bit misleading. Cheers!

  2. kevin says

    January 6 at 7:41 pm

    @faz

    thanks for the feedback (and yes, it was a stock photo)

    kevin

  3. Robert Hall says

    January 31 at 6:32 pm

    The photo above the article is showing the incorrect direction for wrapping Teflon tape (assuming that the pipe has RH threads).

  4. Andy Olejarz says

    May 23 at 10:38 pm

    I think the photo shows the correct direction, so the exposed tail of the tape doesn’t get mashed up, it goes with the direction of the female threads sliding over it.

  5. kevin says

    May 28 at 3:08 pm

    Hi Andy-

    Thanks for your feedback. Yes, the earlier comments were made to the stock photo that had incorrect wrapping direction. Since then, that picture has been replaced with my own (what you see now).

    Thanks

    Kevin

  6. JR says

    August 20 at 7:44 am

    DuPont name is now Axalta. You may want to update that information before some cooperate freak show tries to shut down your site. Great info, thank you.

  7. kevin says

    August 27 at 8:43 am

    @JR-

    Thanks for the heads up!

  8. walt says

    December 6 at 3:21 am

    Hey Kevin! Been a pipe fitter propane tech,(no license of course) I think your info is right on during any gas or propane ppropane install I have done 2 today! There is always a problem thread!!The nearest store is 50 miles and doesn’t stock much.anyway I always carry several rolls of yellow!! And #5 pipedope! If you can’t fix the joint with that combo it’s time for a beer!! Start fresh with new parts tommorow!! Frustrations a DIY most common mistake! Good info thanks.

  9. Milo says

    February 11 at 7:41 am

    I am surprised you did not mention the Third type of pipe sealer, which is the oldest, and also the BEST, especially for iron pipe. I have had Teflon leak, and I especially have had pipe dope leak. I won’t use the dope any more unless there is a compelling reason. Question: What do you think they used before there was Teflon? Pipe Stick is the best if it absolutely has to seal the first time, again especially for iron but works very well with brass and copper. And unlike Teflon, you cannot apply too much. Plus for joints out in the weather, spreading it around exposed threads provides a perfect rust preventative. You can throw a pipe stick in your toolbox and it will remain usable for decades. Just peal the hardened skin off. And it doesn’t blow out the threads like dope will.. Doesn’t shred either. And if you do have to take a joint apart, you don’t have to pick the Teflon out of the threads, especially female.

  10. kevin says

    February 11 at 8:40 am

    Hi Milo

    Thank you for your comment about the pipe stick. Can you recommend a brand or two that you use on a regular basis? The only pipe stick I used were epoxy putty (which I avoid due to it permanent nature).

    Thanks

    Kevin

  11. Mikey says

    November 2 at 10:08 pm

    Concerning your updated photo, what Faz also mentioned about the original photo concerning which side of the tape to use is also true when the diameter of the roll is larger than the diameter of what you are wrapping. For that condition, (most common) it is easier to have what was toward the inside of the roll be on the outside of the fitting in order to control the tension as you are wrapping, i.e flipped around from what you show.

  12. kevin says

    November 6 at 2:31 am

    @ Mikey-

    that is also a good suggestion. thank you!
    Kevin

  13. David says

    January 2 at 2:36 am

    Since Oatey’s Yellow Gas Line Thread Seal Tape With PTFE has a temperature range of up to 500 degrees Fahrenheit, would it be suitable to seal the joints (where male segments go into female ones) of the exhaust vents of dryers, water heaters, and the central heating system of my house?

    If not, what is an appropriate tape? It must be able to withstand high temperatures.

  14. kevin says

    January 3 at 8:42 pm

    @ Hi David-

    To seal exhaust vent duct work, use foil tape (I use 3M foil tape or Nashua foil tape, depending on which one is on sale).
    For water heaters (assuming water pipes), just use a regular white tape;
    For central heating duct work, use water-based mastic sealant like this one. I would use the yellow tape for natural gas applications only.

  15. Garry Miller says

    March 26 at 7:54 pm

    I have noticed propane fittings with a yellow/white sealant that is hardened. No one talks about this sealant. Example is the orfice fitting in a gas grill. What is it?

  16. kevin says

    March 28 at 5:44 pm

    @ Gary-

    I am not aware of any special sealant used in propane fittings, other than a yellow ptfe and pipe dope

  17. Kelly says

    May 5 at 2:18 pm

    I recently helped my sister move into her duplex where the existing gas connection for the dryer was not in code. I replaced the gas line coming off of the existing valve where the gas shutoff was located. I used a flexible conversion gas dryer kit with appropriate connectors. I also used yellow teflon tape at all the connections and soaped to make sure there were no leaks when done. Within 2 days the gas smell in her duplex was so intense, she called DTE gas to investigate. They came in and said that the yellow teflon “gas” tape should NEVER be used and this was the source of the leak!!! Why would places ever sell this to the public if it’s not supposed to be used to seal connectors?

  18. kevin says

    May 7 at 7:02 pm

    @ Hi Kelly-

    Sorry to hear about that. I think the use of tape is dependent on where you live and even, which gas company you deal with.

    For example, when I worked with my gas company, they told me to not use any tapes when joining “black (supply) pipes” but that I could use the tapes when connecting the last leg of the supply pipe (post shutoff valve) to the appliance.

    Kevin

  19. Tim says

    June 24 at 6:43 am

    I am connecting an “H” burner to a stubbed & capped, ready to use natural gas supply line to the fireplace in my living room. The gas line and fire place are new construction and neither have ever been used. The “H” burner is also new and is appropriate for use with natural gas.

    Question:
    Is it OK to use yellow gas tape instead of pipe joint compound to connect the final connections inside the fireplace on this installation ?

    Many thanks for any guidance here.

  20. kevin says

    June 24 at 4:29 pm

    @ Hi Tim-

    I believe Oatey tape is rated up to 500 degrees but I am uncertain if it was meant to be used in direct flame.

    You should contact your local plumbing inspector to determine the correct method of sealing your H burner

    Thanks

    Kevin

  21. Kirk says

    January 4 at 12:59 am

    Can I use yellow tape on water pipe?

  22. kevin says

    January 4 at 7:26 pm

    @ Kirk-

    I would not. Yellow tape is thicker that is suitable for more coarse threads. use the white tape on water pipe threadding

  23. Jim says

    October 24 at 9:58 pm

    Can I use white tape for a gas dryer connection?

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