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Pipe dope on flare fittings

Ken_8 Member Posts: 1,640
In addition, no dope is required on the actual flare joint; obviously the pipe thread aspect of the male (or female) X flare adapter DOES require dope. Just don't use teflon tape on it either (if a gas; LP or NG)

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  • Edward A. (Ed) Carery
    Edward A. (Ed) Carery Member Posts: 138
    Pipe dope on flare fittings.

  • Edward A. (Ed) Carery
    Edward A. (Ed) Carery Member Posts: 138
    Pipe dope on flare fittings.

    I know that it is not proper practice to use pipe dope or tape on the flare end of flare fittings. However I am looking for some kind of an authoritative document to substantiate it. This is an L.P. system.

    I checked in NFPA 54, (National Fuel Gas Codes) and NFPA 58 (LP Code) and it just states that if you use flare fittings, that they should be used for proper applications and pressures. Nothing about the actual installation of a flare fitting.

    The instructions that came with the gas valve are unclear at best. It states that it is ok to use pipe dope on the fittings of a gas line, but not on the first two threads.

    It does not say anything about the type of fitting, and I am sure that they just failed to state that they are referring to a threaded pipe connection, not a flare fitting.

    Any help would be appreciated


    Ed Carey
  • lchmb
    lchmb Member Posts: 2,997

    A flare fitting is designed not to need any pipe dope. As to the gas valve you want to be careful not to get pipe dope into the gas valve as this will damage it. I will say I have seen alot of flare fitting's with pipe dope on them and after removal never have a leak. If done right it's not needed.
  • Tony_8
    Tony_8 Member Posts: 608

    on flare fittings not necessary, but usually won't bother anything if not gotten into the tubing. Tape is a definite no-no as it may impede the make-up of the flare nut causing a loose, leaky joint.
  • David Sutton_6
    David Sutton_6 Member Posts: 1,079
    dope on a flare

    the only reason i see for the adding of dope is just to help the two fittings tighen up with out skipping as you tighen it
  • Dave Stroman
    Dave Stroman Member Posts: 762

    I always say, when in doubt, dope it.

    Teflon tape? I do not know how many leaks I have had to fix until I started using both dope and tape on both gas lines and all threaded fittings. Now it is rare. There is no better feeling, well maybe a couple, than when you can air up a system and have it not drop in pressure. Even a little bit. Sorry, but the tape stays.

    Dave in Denver
    Dave Stroman
  • Bob Harper
    Bob Harper Member Posts: 988
    flex appliance connectors

    Ed, Dormont Mfg. for one forbids dope on the flare ends of their flexible appliance connectors. I haven't checked lately but I think most of the CSST mfrs warn not to dope their mechanical couplings, which are 82degree flares.
    As for regular gas flare fittings, I've researched the same and never found it. You might try contacting Rich Waddington at PECO. He's their tech guru.
    You might also get a gas valve mfr. to decry the practice as it is known for clogging valves. High pressure leak testing, dope and 110 vac are the three biggest valve killers I know of.
    Best regards,
  • Ken_8
    Ken_8 Member Posts: 1,640

    Just be prepared to have the lawyers eat your lunch when they find your teflon tape fray downstream, blocking the pilot orifice and shutting the boiler off, the pipes all frozen and damages in the hundred thousand range from a small fray of tape causing a freeze up in the dead of winter.

    Or worse yet. The teflon fray gets stuck under the main gas valve and seat and keeps the gas on and lit after the stat's satisfied and the furnace, boiler, water heater bounces off the high limit for a week while the homeowner's in Timbuktu dancing with wolves...

    Why not try, teflon tape pipe dope and plumbers wicking? Hell, if two's good, three's better!

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  • Weezbo
    Weezbo Member Posts: 6,232
    flare is metal to metal.

  • bob young
    bob young Member Posts: 2,177
    schmear vs. dry

    flare consisered ground seat,no ?? textbook no lubricant necessary----but then you got the real world and field conditions. i always schmear the face to prevent galling. even unions
  • S Ebels
    S Ebels Member Posts: 2,322
    Don't know if it's right or not

    But it seems to help. We always dab a light coating, no, film is more like it on the flare fitting for gas. Not so much for the sealing properties of the dope itself but to add a little "slip" to the joint when tightening up. The interface of the nut and fitting is the seal but we've found out in the field, where sometimes alignment issues cannot be avoided, that the added "cush" factor of the dope allows the fitting and copper to move into place better than no lube at all.
  • Dale
    Dale Member Posts: 1,317

    Use a little "leak lock" on refrigeration flares since the pressures are high, I don't use it on gas although a bit wouldn't hurt to help get the nut a little tighter. Most bad flares (leaky)on gas I've seen came from inadequate reaming. The only time we use teflon tape with gas is 4 inch threads which get tape and dope.
  • Dan n
    Dan n Member Posts: 1
    pipe dope or teflon on flare fittings

    teflon is a no-no on flare fittings and gas systems in general ! it will break down and get stuck in the gas vavle or appliance reg.

    there is no need for pipe dope on flare fitting either,check the flare and or the fitting for burr's and retighten
  • oil-2-4-6-gas
    oil-2-4-6-gas Member Posts: 641

    grease --i use a very small film of grease on my flares -never a problem yet --along with using the Ritchie "bicycle grip" flare-tool
  • gerry gill
    gerry gill Member Posts: 3,072
    so.....is the yellow gas tape,

    supposed to be used for water?
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Glen
    Glen Member Posts: 855
    our gas code ...

    allows t tape - that is approved for gas line applications. Yes - it is Yellow - but can be blue or other colors as well. It's the gas code cert (CSA) that is important. We use both t tape and pro dope on all threads over one inch. Rarely have a leak. On our csst and copper flares we use a lube on the flares - again with great success. All this by code or field experience to eliminate leaks and other problems. Liability issues???? The code demands zero leaks -
  • Edward A. (Ed) Carery
    Edward A. (Ed) Carery Member Posts: 138
    Back to the original question

    To all who responded, thanks.

    This has been a good thread but it has gotten a bit off the point.

    It appears that the majority (myself included) suggests not using pipe dope or tape on the "flare end of flare fittings". I was taught not to use dope or tape on the FLARE end.

    What I am specifically looking for is some kind of an authoritative document that says that "you can", or, “you can not", use pipe dope on "the flare end of a flare fitting".

    I know that the CSST mfg spell out in their instructions that they do not want any sealants used on the flare connection point, but I am talking about a standard 1/2" flare fitting, for an LP gas line using standard soft copper tubing.

    I have no problem at all using the properly rated dope on the M threaded end of a F x M adapter, but I am talking about the flare end.

    It seems, (again myself included) that everybody can say that you should not use pipe dope or tape on the flare end, but none of us can actually say why.

    We were all taught that way by someone, but I have yet to find any actual document that spells out the correct way to do a flare fitting in respect to the use of sealant on the surfaces and threads on the flare end.

    Thanks to all, and any additional help will be appreciated

    Ed Carey
  • Tony Conner_2
    Tony Conner_2 Member Posts: 443
    I'd Ask...

    ... the manufacturer's of the flare fittings, and see what they recommend.
  • Weezbo
    Weezbo Member Posts: 6,232
    on gas of any sort you have a regulator or lets say you are

    supposed to have a regulator,gas goes whisteling past the fittings,supposedly carrying along just about anything and every thing in its path,this material is then collected supposedly in the Drip legs we put ahead of the appliances or where ever we have them installed,should a piece of teflon or rope or banana whatever zip by the drip leg it could get stuck in the regulator which in turn could cause reliability issues (lets call them )interfering with the safe and proper functioning of the appliance or equipment. does that mean bag regulators? nope*~/:)
  • Bob Harper
    Bob Harper Member Posts: 988
    Copper Handbook

    "No material (e.g., pipe joint
    compound) should be applied to the
    mating surfaces of the flare fitting and
    the flared tube end before attaching the
    flare nut to the fitting body."

    How's that, Ed? Page 53 of the Copper Tube Handbook, put out by the Copper Development Assn. Free PDF at www.copper.org/

  • Edward A. (Ed) Carery
    Edward A. (Ed) Carery Member Posts: 138
    That is great


    That is a home run. Also, that is a great resource site.

    Thank you,

This discussion has been closed.