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  1. #1
    Join Date
    Jul 2004
    Posts
    322
    I noticed that I have a flexible gas line going through my furnace cabinet. From what I've read here and seen on home inspection shows, hard (black) pipe should go through the cabinet. I think I can handle this but was wondering if there is a preferred pipe dope or gas teflon tape that you prefer. The threaded fitting right at the gas valve now looks like it has a blue pipe dope.

  2. #2
    Join Date
    Nov 2004
    Location
    Jonesboro, Arkansas
    Posts
    122
    I usually use teflon tape seems to work ok, if you don't have a drip leg I would put one in while I was at it.

  3. #3
    Join Date
    Aug 2004
    Location
    Boston, MA
    Posts
    110
    You should never use teflon tape on nat gas. I believe it's againsed code in Ma.Rectorseal is the most common pipe dope used on nat.gas but there are other brands that will also work.

  4. #4
    Join Date
    Oct 2004
    Posts
    3,400
    Read the label.

  5. #5
    Join Date
    Jan 2005
    Location
    Gilroy, Calif
    Posts
    188
    Most home inspections will note that hard pipe should be used through the cabinet of a furnace. However, a flex line should be installed from the hard pipe to the furnace control. If there is adequate space around the flex line you now have installed and it is of approved material,you should be fine. The problem with flex lines going through the cabinet, without proper clearance, is in the event of vibration from the fan or other sources may cause a hole in the flex line rubbing on the steal shell. You can cut a small section from an old garden hose, slice it down the middle and install it around the flex and secure it with wire ties. Works great and usually does the job. Check with your local professional HVAC dealer for any more questions.

  6. #6
    Join Date
    Nov 2001
    Location
    Moose Jaw, Saskatchewan, Canada Occupation:Interprovincial Plumber, Commercial Gasfitter Interests:
    Posts
    2,411
    Why should a flex be installed from the hard pipe to the furnace control??????????????????????
    I love my job, but paydays Thursday

  7. #7
    Senior Tech Guest
    Garden Hose...flex pipe, wire ties...gas pipe...which 3 don't fit...black pipe all the is the only way to fly.

  8. #8
    Join Date
    Nov 2003
    Posts
    501
    Originally posted by rich pickering
    Why should a flex be installed from the hard pipe to the furnace control??????????????????????
    I think he meant the gas shut off for the furnace.

    I don't care what he says though, flex line should NOT be run inside the furnace. Even with a hose wrapped around it. NEVER!

    As for the OP's question on dope vs. tape, out here, it is against code to use any type of teflon tape on gas lines. It's dope all the way.

  9. #9
    Join Date
    Dec 2002
    Location
    Tampa, Florida
    Posts
    706

    Post g

    i prefer black pipe all the way myself, but here in tampa area, code allows for use of flexible steel tubing. i use rectorseal pipe dope only, specifically listed for use on gas connections on the can! seen many installs w/ very large hole to accomodate tubing, but no protector ring at unit penetration. i keep several sizes of hard, black plastic knock out bushings. i cut one side so i can slip it on to the tubing(trying to avoid disturbing a perfectly good seal to the gas valve). i then use some super or krazy glue to mend the slice i made. finally double check seal at valve shut-off and connection at furnace using bubbles made for gas leak detection! safety, safety,safety!! i tell my client it will be an additional $12 fee, but if they sqeek when they walk or complain, i give it away for free. my conscience won't let a thing like that go unprotected. i guess i care more about their safety than they do? less than one dollar in parts.

  10. #10
    Join Date
    Feb 2004
    Location
    chicago suburbs
    Posts
    4,422
    Originally posted by senior tech
    Garden Hose...flex pipe, wire ties...gas pipe...which 3 don't fit...black pipe all the is the only way to fly.
    listen to this guy here...black iron all the way in.
    i use both tape and dope.


    the tape is the sealant and the dope is the lubricant.
    FILL OUT YOUR PROFILE!!

  11. #11
    Join Date
    Jan 2005
    Location
    Gilroy, Calif
    Posts
    188
    Miss understood my post. Flex lines are used for exactly what is says. Flexibility. If you live in earthquake territory, a must, if you don't, than hard pipe it to the gas control valve. The garden hose theory is only a protective shield AROUND the flex line through the furnace cabinet to protect it form being worn and causing a hole in the flex line due to vibration. I'm sure you've seen the rubber grommets installed in the punch out holes, maybe not. Come on guys, really! You like dealing with hard pipe to the control valve or would you rather deal with a flex line from gas shut off valve to the gas control valve if you have to make repairs. They make a Teflon tape for Natural or L.P. gas and as mentioned Rectorseal is a good product to use. Some contractors use both when dealing with large pipe. Rectorseal than wrapped with Teflon, I think it's a waste but whatever the boss wants. Black pipe all around is a great idea but, seen otherwise thats been there for 50 years. New installs should never have flex lines through metal frames. Will not argue that point, never should be and inspectors won't pass it.

  12. #12
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    How come everyone gets there sh*t in a knot when it comes to gasfitting. You guys must realize what is code in one place is not code in another. Black pipe, flex, copper tubing, any one of these is allowed in one place or another. To say that something is not allowed "teflon tape" is just plain dumb when it is readily available in other areas of the country and it also legal and labeled for gas use or propane. If you are going to tell someone something is illegal, I hope you are aware of the gas code in their area not just your own little fish pond.

  13. #13
    Join Date
    Mar 2005
    Location
    Houston, Texas
    Posts
    11,831
    Copper tubing? I don't think so.

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