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Thread: Cap for gas line needed

  1. #1
    Join Date
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    Cap for gas line needed

    Trying to cap off a propane line in a fireplace. It’s a 5/8 male so need a female cap. I bought one with FIP threads but it’s the wrong type thread, it threads on very loosely and wobbles. The one I tried was not a flare type. Anyone know which type I need?
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    Last edited by Bruce King; 01-01-2021 at 11:14 PM.

  2. #2
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    Peshtigo,WI
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    That's a tapered fitting, similar to a hydraulic fitting, not pipe threads. Your 3/8 FIP might fit one of those other fittings farther up the line.
    Confidence: The feeling you experience before you fully understand the situation

  3. #3
    Join Date
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    Difficult to say as to size, but I would remove the flare fitting and put a 1/2 or 3/4” normal cap on the IPS thread.

  4. #4
    You have a flare fitting. I suspect 1/2.
    I would remove the adapter and reducing bushing and install a NPT pipe cap. Which I think is 1/2 NPT, but it's hard to judge.

    1/2 pipe, 7/8 OD
    3/4 pipe , 1 1/8 OD
    1/2 tube, 1/2 OD

    If you measure the OD of the tube you took off, it will give you the flare cap size.

    Flared Fittings,

    https://www.mcmaster.com/1774N33

  5. #5
    Oops,
    Wrong link.

    McMaster-Carr Page:
    https://www.mcmaster.com/Standard-Fl...r-tube-od~1-2/

  6. #6
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    Looks smaller to me. 3/4" is big for propane. 1/8 or 1/4 more likely. But I'd look at capping closer to the source, less chance of a dangerous leak.

  7. #7
    Join Date
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    Quote Originally Posted by Tom Bender View Post
    Looks smaller to me. 3/4" is big for propane. 1/8 or 1/4 more likely. But I'd look at capping closer to the source, less chance of a dangerous leak.
    That was my thought - if the propane is still used elsewhere in the house trace that line to the source and either cap or valve it there, depending on whether it might be needed in the future.

    Speaking of gas line sizes, the biggest I've seen is a 2" gas line into a friend's place. (Natural gas) The line feeds the pottery kilns in his shop and when he opens the valves money starts evaporating from his bank account!

    JKJ

  8. #8
    The knockouts in the background are 7/8. It looks like 1/2 and 3/4. 3/8 pipe has a different pitch. A tape measure would solve this.

  9. #9
    I do not know the size but I did run a propane line from my tankless water heater to my fireplace and my bbq grill. I used black iron pipe for the little bit that is in the wall of my house (going to the grill) but the rest is soft copper. I was able to get all the fittings I needed but some I had to order on line. Big box stores has some but not nearly all I needed. A local hardware store had more selection but still did not have everything. Long way of saying you may want to look on line. Whatever you use, use a little pipe dope made for gas lines or a little teflon tape that is made for gas (it is different from the tape for plumbing). I was frustrated that it was so difficult to get what I needed but I think that may be because most DIYers do not mess with gas or propane.

    As an aside, when my fireplace was installed the installer checked most of my connections and found them sound. He tightened one a little bit. That made me feel better. But soapy water will tell you if it's leaking. I bought a little bottle of it to get the applicator but dishwashing soap in water will work.

  10. #10
    Join Date
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    Quote Originally Posted by Jim Dwight View Post
    ...
    As an aside, when my fireplace was installed the installer checked most of my connections and found them sound. He tightened one a little bit. That made me feel better. But soapy water will tell you if it's leaking. I bought a little bottle of it to get the applicator but dishwashing soap in water will work.
    Best thing I've found for testing for leaks from pressurized fittings is soap bubble solution. I use it for air lines, gas lines, bobcat tires, etc. This will form even very tiny bubbles easier than a soap mix and hang around much longer. I bought a couple of gallons of soap bubble solution for $1 from Walmart one year at the end of the summer season.

    BTW, for gas lines an inexpensive sensor is nice to have in the kit. I bought this one when I thought my propane cook range top had a leak:
    https://www.amazon.com/gp/product/B07BM1XWB8

    The service guy thought it was leaking but couldn't find where. I wanted to test further. It turned out to not be leaking but to be something entirely different about which I became educated:

    When a large propane tank is almost empty the mercaptan which is added to give that "gas smell" for safety can become concentrated at the bottom of the tank and normal use can make a non-leaking appliance smell like a gas leak. Turns out my tank was almost empty and refilling it eliminated the gas smell. A gas company manager told me this was common. The appliance dealer and service man either didn't know about this or were only too happy to sell a new appliance. Bottom line: I have a spare gas range top in good condition (set up for propane instead of natural gas) if anyone close wants it.

    JKJ

  11. #11
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    Feb 2010
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    Ok, you guys got me motivated to go back to the store or try again to remove that flare fitting. It took about 150ft lbs to get the line off that one. This is a non used line now, no other gas appliances here but capping off as required.

  12. #12
    Quote Originally Posted by Bruce King View Post
    Ok, you guys got me motivated to go back to the store or try again to remove that flare fitting. It took about 150ft lbs to get the line off that one. This is a non used line now, no other gas appliances here but capping off as required.

    They do make flare caps. We work with a ministry at State Fair. During off season, cap all the appliances (WH, range, dryerect) with flare caps to keep bugs from nesting inside fittings. Lowes stocks them.

  13. #13
    Join Date
    Sep 2016
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    Modesto, CA, USA
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    When I bought my minisplit ac the lines were capped. They had the correct forged screw on flare coupling fitting. But the had a small copper dome over the male part held on by the coupler. You had to re use the coupler and flare your own raw copper tubing.
    It maybe easier to find a valve that fits and use that as a seal cap. Or flare a short piece of copper tube and fold it over and crimp it to seal. You could soft solder the crimp if desired.
    Propane is double the pressure of NG so maybe 20" of water column.
    Bill D.

  14. #14
    These are on Amazon--


    lpcap.jpg
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    CASmate, Corel, Gravostyle


  15. #15
    Join Date
    Mar 2014
    Location
    Youngstown, Oh
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    204
    A grill shop could have fixed you up. Gas threads have a 45° taper and hydraulic fittings are a 37° taper. Gas thread sizes are not used in hydraulic thread sizes to avoid a cross over mistake.

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