Gas connection - thread sealant on flare end?

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Hardt

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I am confused about instructions that came with a 4' long flexible stainless steel connector to be used to connect lpg tank to range. It gives strong warnings not to use thread sealant on the flare threads. Now I can understand that you would not want to put sealant on the flare end itself because it would interfere with the metal-to-metal mating with the flare seat but how would sealant on the threads somehow keep the flare joints from mating properly? After reading a few posts about the "best" sealant, I bought a tube of Rectorseal 5 and plan to use it instead of teflon tape for this project. I thought I would disregard this warning and apply sealant sparingly on the back half of the flare threads, far away from the flare end to not contaminate it but I don't want a leak so I thought I would check with the experts on this forum. Please offer your advice if you can. Thanks.
 

Randyj

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The flared end, I assume, is copper which is a soft metal and should seal with no problem. The reason for the warning against using a sealant is, as you have surmised, to prevent the sealant from getting in the orifice and other places blocking the flow of the gas. Before you apply sealant you might want to do a soap bubble test. Go ahead and hook it up and turn the gas on, take a cup with a generous amount of dishwashing liquid, add warm water and mix it up really good then spray or use a small paint brush to really slop it on the fitting and threaded area really good. You will have some bubbles from the soapy water..but look for new bubbles forming... if you can get it on without any bubbles .. that's great..then look for bubbles. No bubbles = no leak..and you're in good shape.
 

Jadnashua

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Pipe threads are tapered, they get tighter the further you screw things together, but things can leak around the thread, so you need tape or dope to fill the gaps and make the seal.

The threads of the nut that holds a flare fitting or a union together are like those on a screw or bolt - the only reason they'd get tight is if they bottomed out - there are not intended or capable of making a seal except to compress some fitting or gasket material together so the mating surfaces are jammed together and make a seal. Sort of like the threads on your water hose...it is loose until you compress the washer. So, no joint compound or teflon tape is needed or wanted on those threads. A drop of oil might help you to tighten it enough to compress the mating surfaces, though, depending on what you are doing.
 

Randyj

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Thanks Jad.. I knew that but didn't know how to put it in words... excellent comparison. My dead brain comes to life from time to time (brain farts)....
 

Hardt

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Ah, Ok I think I understand the concept now!! Tapered screw connections use tightness to achieve water/gas intergrity but non-tapered screws connections are mainly to provice mechanical compression and the integrity is provided by a compression ring, flare joints, etc. But still, what would be wrong by using sealant on the threads since it would provide the lubricant that you mentioned and also allow a second line of defense should there be a leak at the flare matings, compression ring, etc?
 

Randyj

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Randyj said:
The reason for the warning against using a sealant is, as you have surmised, to prevent the sealant from getting in the orifice and other places blocking the flow of the gas.

This is the best answer I can come up with at this time.
 

hj

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sealant

Maybe so, but I ALWAYS use joint compound on the flare ends to make sure any irregularities are filled. It also lubricates so things go together the way they are supposed to. An engineer put that warning on the connector, but he never tried to actually assemble one.

pipe-dope-dope-2.jpg
 
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Kordts

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I was doing some repairs at our pastor's apt. I opened up the door to the utility room and smelled gas. I squirted bubble on the gas flexi. It bubbled at the flare adapter coming out of the gas cock. I pulled it apart and about puked. A teenager trying to be helpful, using the skills and know-how his dad taught him, installed the dryer for our pastor. He wrapped electrician's tape around the flare instead of thread sealant. A typical DIY brainstorm with possibly deadly consequences.
 

Randyj

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Definitely true... I ALWAYS check for leaks after connecting a gas line. If I can't find soap bubbles or anything else I'll at least spit on it. Not worth taking chances.
 

Hardt

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Ok, thanks for the lesson and all the opinions. I knew about tapered and non-tapered screw fittings but did not relate the two types to the use/non-use of sealants. I've operated under the principle of if the matings are metal-to-metal, use a sealant. If plastic-to-plastic or plastic-to-metal a sealant is redundant because the plastic is compliant enough to "fill-in" any irregularities in the machined surfaces. After reading Jim's explanation, I've gone back and re-read the instructions of my last plumbing experience: installing a kitchen faucet and there is NO mention of having to use a sealant for the supply fitting to faucet fitting connection!! However, HJ says he ALWAYS uses sealant at a flare connection so I plan to go with my initial inclination and use a sealant carefully and sparingly at the flare end. For other future water plumbing projects however, I will experiment and skip the teflon tape and rely on the flare ends, compression ring, rubber gasket, etc. to give me a leak-free connection. For gas connections I will use a sealant for the extra insurance it provides. Thanks again for all the inputs!
 

Randyj

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The big trick on flared ends is to have good, smooth mating surfaces. Once it's torqued down your only danger is over/under torqued flare nuts.
 

Bob NH

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kordts said:
I was doing some repairs at our pastor's apt. I opened up the door to the utility room and smelled gas. I squirted bubble on the gas flexi. It bubbled at the flare adapter coming out of the gas cock. I pulled it apart and about puked. A teenager trying to be helpful, using the skills and know-how his dad taught him, installed the dryer for our pastor. He wrapped electrician's tape around the flare instead of thread sealant. A typical DIY brainstorm with possibly deadly consequences.

New Hampshire lets people do plumbing and electrical work on their own houses, and had even allowed gas work by homeowners. However, a recent fatal explosion resulted in a state law that permits only licensed persons to do any gas work.

One possible consequence of using any kind of lubricant on the threads of a flare or compression fitting nut is that it increases the load resulting from a given torque. I saw one case where Loctite was slobbered onto the threads and face of a large nut and provided so much lubricating effect before it set up that it caused failure of the fastener when the specified torque was applied.
 

Hardt

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"Over torquing" ouch, another fly in the ointment!! :) Yes, many years ago when I first started working on my cars I always wondered about the accuracy and consistancy of the torquing processing. If you are working on a new installation with brand new fasterners, I would expect that you can be confidant that you can torque all the fasterners precisely and accurately. If however, you are working on an old car that has been out in the elements, and the fasterners are rusty, greased, heated, banged up, etc. how can you expect to torque accurately. Maybe one of you mechanical engineers can enlighten me on what conditions need to be present to set an accurate torque. BTW, I do have torque wrenches but don't have an adapter to use for this application.

Getting back to this topic, I have the installation instructions for the gas range-to-gas supply and it says to apply teflon tape or an appropriate thread sealant to ALL male pipe threads. This is contrary to the instructions that came with the flexible connector. Go figure...

So to close this thread, if you all never hear from me again, I've blown myself up and I've instructed my wife to put on my headstone: " I shoulda stuck with the electric range!"".
 

Gary Swart

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I'm not a pro, but I have 100% gas appliances in my home and they are all connected with a flex pipe. I used no sealant of any kind on any of them and have never had a leak. I always check every joint/connection with dishwashing detergent just to be sure. I have found some small leaks on my lines, but never on a flex connection. BTW, I use Oatey pipe compound on my joints, no tape.
 

leavittkeith10234

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New Hampshire lets people do plumbing and electrical work on their own houses, and had even allowed gas work by homeowners. However, a recent fatal explosion resulted in a state law that permits only licensed persons to do any gas work.

One possible consequence of using any kind of lubricant on the threads of a flare or compression fitting nut is that it increases the load resulting from a given torque. I saw one case where Loctite was slobbered onto the threads and face of a large nut and provided so much lubricating effect before it set up that it caused failure of the fastener when the specified torque was applied.

I have not heard of Loctite having an impact and effect on the torque of a fastener before, yet I have never worked with people that have used much of it in the rare cases they use it. Anti-Seize is used every where needed by the people I have known, with a very sparing use of Loctite on rare occasions when needed, as they put things together and take them apart often for a living. Good to know that goop uses can impact torque applications of specific calibers if used incorrectly, yet I have not experienced this yet. I do appreciate the story and sharing of that advice though.
 

leavittkeith10234

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"Over torquing" ouch, another fly in the ointment!! :) Yes, many years ago when I first started working on my cars I always wondered about the accuracy and consistancy of the torquing processing. If you are working on a new installation with brand new fasterners, I would expect that you can be confidant that you can torque all the fasterners precisely and accurately. If however, you are working on an old car that has been out in the elements, and the fasterners are rusty, greased, heated, banged up, etc. how can you expect to torque accurately. Maybe one of you mechanical engineers can enlighten me on what conditions need to be present to set an accurate torque. BTW, I do have torque wrenches but don't have an adapter to use for this application.

Getting back to this topic, I have the installation instructions for the gas range-to-gas supply and it says to apply teflon tape or an appropriate thread sealant to ALL male pipe threads. This is contrary to the instructions that came with the flexible connector. Go figure...

So to close this thread, if you all never hear from me again, I've blown myself up and I've instructed my wife to put on my headstone: " I shoulda stuck with the electric range!"".

I like your share. I don't know the setting for perfect torque conditions as an engineer might explain, yet I do know a think or two about torque requirements and mechanical actions. I come from a long line of people that torque, and am not sure if I know anyone that twerks, at least not the torque types I know. Now, in the field of Electrical there is a desire, and near demand (manufactures recommendations applied as code under follow manufactures guidelines being a code in NEC) torque screw drivers are available, as breaker connections, and terminal post connections all have a torque guideline now.

The principles of torque calculations in electrical connections is interesting, as it relates to hot spot connections. An over tightening, or loose connection can cause hot spots with meters of infrared types or odd readings. They make many types of torque tools now, and desire for many things to be torqued in many settings, a slow integration into the industry wholly still, even in the "new construction" arena that implements changes first. Torque of a tire, isn't about the heat, and I am not sure the ideal conditions.
 

leavittkeith10234

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Ok, thanks for the lesson and all the opinions. I knew about tapered and non-tapered screw fittings but did not relate the two types to the use/non-use of sealants. I've operated under the principle of if the matings are metal-to-metal, use a sealant. If plastic-to-plastic or plastic-to-metal a sealant is redundant because the plastic is compliant enough to "fill-in" any irregularities in the machined surfaces. After reading Jim's explanation, I've gone back and re-read the instructions of my last plumbing experience: installing a kitchen faucet and there is NO mention of having to use a sealant for the supply fitting to faucet fitting connection!! However, HJ says he ALWAYS uses sealant at a flare connection so I plan to go with my initial inclination and use a sealant carefully and sparingly at the flare end. For other future water plumbing projects however, I will experiment and skip the teflon tape and rely on the flare ends, compression ring, rubber gasket, etc. to give me a leak-free connection. For gas connections I will use a sealant for the extra insurance it provides. Thanks again for all the inputs!


Alright, I may or may not be an expert. I have worked with many greats, many good enough, and a few of what I call the greatest of their craft through my life. There are many types of goop, goops for all needs, each having a use, in a time and place. You must know your goops and where to use them. Teflon tape is used like a goop and the most incorrectly used item on threads that I have ever ran across in my life. Loctite is a wonderful goop that I may have only used less than one hands worth of counts or like twice, as it shouldn't be needed in almost nearly all settings (the sever loctite not the loctite brand). Loctite brand, just to say, does also make many wonderful goop. There are certain goops only available in certain brands from certain suppliers, that one day you may take a personal liking to one goop over another from suppliers and wholesalers, Dap is an interesting company few use regularly.

That all said. Plumbing is where many of the goop are most incorrectly used, and I am still learning goops. I know how and when to use, and most importantly, when not to use teflon tape. That is the key to get down. Yet, there is the temping, "See if Teflon Tape will stop the leak," error of so many. Teflon you seem write on, as metal to metal threads, most commonly, unless the fitting is compression type variation. A compression type variation could be flange ring connection of many variations, the rubber gasket internal flange, you will find on the faucet connection lines, to sinks, toilets, and such. Your garden hose doesn't probably have a compression class of connection, as most don't, yet use a flat washer that gets compressed to seal, yet allows for easy disconnection and re-connections. Compression fittings are often rarely changed or disconnected, yet are used in places of disconnect and re-connections without the Teflon or thread treatment needed if done right, nor recommended. Plastic plumbing line should never really need Teflon Tape, yet rarely, it might help, if used on the right connection type of plastic following the rules of Teflon Tape, until the part can be replaced, due to Teflon never really seeming to provide a good fix to plastic thread items, like metal to metal. Teflon is used where the threads are part of the seal against leak. Again, Teflon is used where the threads are part of the seal against leak. Compression fittings are designed where the threads provide torque to compress the bevel, farell, or ring or such that holds from leak. No Sealing agent or compound, or Teflon Tape is needed in this case, or could mess up the torque.

The most common plastic connection that is sealed with Teflon improper is drain systems under sinks of plastic parts, yet on one rare type of system, there is one location that holds a lower pressure (all drains are low pressure, yet a back pressure location) point with the threads. Teflon, may or may not be allowed in this location, yet shouldn't be needed still.

Gas line goop, is essentially the same, where the thread holds the leak, goop away to manufactures recommendations, where the fitting is compression, the manufactures of compression fittings have designed their fitting for no goop. This sometimes means making some compression fitting connections two or three times to seal without leaks, using a few extra parts at times.

I don't know if this helped, was read, or is just one big wasted ramble.
 

hj

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I have never seen the term "goop" used so many times in one place. I assume it is some sort of "technical term" since there is only one tube I have EVER seen it used on. Conversely, about the ONLY time I use TPFE, (there is NO Teflon), tape is on PVC male/female threaded connections.
 

Gary Swart

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I dislike the TPFE tape so I always use Oatey joint compound. However, just a couple of days ago, I removed my shower head and soaked it in CLR. Put it back on the pipe, using joint compound, and don't you know, it leaked! Made a trip (2 blocks) to Ace Hardware and get a roll of tape. Came home, put two wraps on the pipe and reinstalled the shower head. Guess what...still leaked. Took the head off, put two more wraps on, reinstalled the head, and finally success. Don't know what I'll do with the rest of that tape, put the shower head is good. Seventy years ago, I remember my dad using the goo from the bottom of lead paint to seal galvanized pipe. I have no idea if there was commercial sealant in those days, but the paint seemed to work.
 
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