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Thread: Sizing gas line for new outdoor BBQ

  1. #1
    DIY Junior Member kefxb24's Avatar
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    Default Sizing gas line for new outdoor BBQ

    I have used this forum and other information sources to research the required size of a gas line extension for an outdoor BBQ. I have attached a diagram showing the existing natural gas appliances and facilities at my home located in Chester County, PA - a suburb of Philadelphia.

    Using Table 402.4(2) for Metallic Pipe of the 2012 International Fuel Gas Code and 125' as the maximum length for the run, an extension utilizing 1/2" pipe appears to sufficiently service the new grill, but just barely.

    Since hard pipe is my least attractive option considering routing under an overhand and a deck, I would prefer to use CSST or PVC coated copper tubing such as Gas-Tec/GasShield. According to IFGC tables 402.4(9) for Semirigid Tubing and 402.4(15) for CSST, 1/2" copper or ED18 CSST tubing is insufficient for the grill extension. A minimum 3/4" tubing or ED25 CSST appears to be required. (I get the same result if I substitute 100' as the maximum run length.)


    1. Based upon the above, have I correctly calculated the sizing requirements for the line extension to the grill?
    2. Am I correct in not considering the backup generator in my calculations because it is fed directly from the meter?
    3. Please provide corrections, thoughts and suggestions on how best to handle this project.


    Thank you.
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  2. #2
    Plumber Sean Beck's Avatar
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    The way I was taught to size natural gas lines, you would need to know the BTU/h of the appliance.

  3. #3
    DIY Junior Member kefxb24's Avatar
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    The BTU for the grill is shown on the diagram, 40k. It also shows the BTUs for the dryer, which is on the same segment.

  4. #4
    Plumber Sean Beck's Avatar
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    Oh yes I see it now. Looking at my Canadian Code, 1/2" would be sufficient for up to 58KBTU/h so you should be okay with that.

    The generator doesn't necessarily have to be considered when sizing the line from the dryer to the grill. When sizing, you work with the appliance furthest away from the regulator. In this case, it turns out that the grill will be the furthest.

    Sometimes there can be a risk that adding an appliance at the end of a run can undersize the piping before it. But your piping seems like its sized okay.

    This is all based on you having a pressure of between 7' and 14" WC
    Last edited by Sean Beck; 11-01-2013 at 03:19 PM.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    11 /4" 1", and 3/4" seem a bit oversized if all you have on the system now is the dryer. If you have a range/cooktop, water heater, and furnace they have to be figured into the mix.
    Licensed residential and commercial plumber

  6. #6
    DIY Junior Member kefxb24's Avatar
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    The inside 1" previously serviced a furnace and water heater; both were replaced with a geothermal system running on electric.

    The range, oven, and backup water heater are also electric. My diagram shows all current appliances utilizing natural gas.

    The exterior 1.25" piping was recently installed when the gas company upgraded the meter to support the backup generator.

  7. #7
    DIY Senior Member Hammerlane's Avatar
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    Quote Originally Posted by hj View Post
    1-1 /4", 1" and 3/4" seem a bit oversized if all you have on the system now is the dryer. If you have a range/cooktop, water heater, and furnace they have to be figured into the mix.
    I'd rather be oversized and have to reduce down with one or two fitting than to be underized and have to possibly replace back all the way to the main.

  8. #8
    Moderator & Master Plumber hj's Avatar
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    The 1 1/4" on the side going to the dryer has absolutely nothing to do with the generator's gas supply, and vice versa. The only consideration is what size pipe will deliver 40 k btus using the 130' length column.
    Licensed residential and commercial plumber

  9. #9

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    Having had a bad experience with CSST, I'd go 1/2" black pipe & you will be fine. I usually follow guidelines, but have always felt that gas pipe sizing was over calculated.

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