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3/4 to 5/8 gas line adaptor

kinghoward
kinghoward Member Posts: 23
in Radiant Heating

The install manual does not help here. A standard 3/4 inch natural gas line, male threaded, comes within 4 feet of the newly installed boiler. The boiler has a male 3/4 inch threaded pipe to hook up to. The adaptor on supply goes to 5/8 and theres a 4 foot standard appliance/furnace flexible line available. Any reason not to use this line? The adaptor at the boiler inlet goes from 5/8 back to 3/4. Seems 3/4 to 3/4 flared adaptors a little difficult to find. Let me know if you need more info. The replaced old boiler had 1/2 inch gas line, fyi. Thanks

Comments

  • mattmia2
    mattmia2 Member Posts: 13,935
    edited September 1

    the gas connector should be replaced with the appliance. it will come with flare adapters.

  • kinghoward
    kinghoward Member Posts: 23

    Ok, the adaptors are flared. Any foreseen problems using the 5/8 inch , 4 foot long, flexible connection line when it goes from 3/4 inch to 5/8 and back to 3/4 again. My guess is it will deliver enough CFM of natural gas. Much appreciated, take care.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 18,415

    As far as I know appliance flex connectors are only supposed to be used for appliances that may need to be moved like a gas dryer or a gas stove. Water heaters and boilers should be hooked up with black pipe or and I hate to say this CSST

  • mattmia2
    mattmia2 Member Posts: 13,935
    https://forum.heatinghelp.com/discussion/comment/1863727#Comment_1863727

    I think that depends on jurisdiction. Some places forbid it, some places require it, usually to keep gas lines from breaking in an earthquake.

  • ratio
    ratio Member Posts: 4,104

    It'll be fine, that's not especially small for an appliance connection. There should be a tag on the whip that gives the maximum BTU/H by the different lengths, but it'll work regardless. Verify the inlet & outlet pressures, both static and operating, if you have any concerns.

    Alan (California Radiant) Forbes
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 18,415

    @mattmia2

    You could be right. about 20 years ago MA required everything to be hard piped even stoves and dryers. But then they changed it back to allowing flex connectors for stoves and dryers.

  • Bob Harper
    Bob Harper Member Posts: 1,123

    The Nat'l and Int'l Fuel Gas Codes allow flexible appliance connectors only when installed to their listed instructions AND, a maximum of 3ft except movable appliances such as dryers and ranges. They cannot penetrate appliance cabinets, floors or walls so the piping upstream and downstream must be properly supported. The connector tag typically will show the BTU rating for the length. No pipe dope or PTFE tape on the flare fittings- NPT threads only. If it whistles, its undersized. Why not just pipe it with hard pipe or CSST if need be? You'll need an approved shutoff, sediment trap and union within 6LF of the appliance control valve. Regardless, leak test, measure inlet gas pressure static and full load as well as manifold pressure. Run combustion analysis and adjust prn.

  • kinghoward
    kinghoward Member Posts: 23

    Very good. Thanks for the help! Awesome

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