Gas Line for outdoor grill 91000 btus

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by stoneweed1, Jun 22, 2013.

  1. stoneweed1

    stoneweed1 New Member

    Jan 31, 2008
    I have natural gas entering the house at 1/4 lb pressure. I am concerned about the size of the 1/2" yellow flex csst line to my grill which requires 91000 btus when all burners are lit.

    The run to my grill is as follows:

    1.5" black pipe runs 40 feet then reduces to
    1.25" black pipe that runs 17 feet then reduces to
    1" black pipe that runs 11 feet to a tee and continues, but at the tee a
    3/4" yellow csst flex trac pipe runs inside 20 feet to the outside where it changes to
    1/2" yellow csst flex trac pipe and runs 20 feet in conduit underground to a tee and off of the tee is a
    1/2" 12 foot flexible quick connect to the grill

    The 1/2" line was there before the grill purchase and there are other appliances that feed off of the black pipe run, however let's just assume that the grill is the only appliance being used when it's lit.

    The trac pipe chart states that a 6" - 7" WC pressure with 0.5" drop will give me approximately 70000 btus @ 20 feet of 1/2" trac pipe and 58000 btus at 35 feet of trac pipe. A 12 foot 1/2" tracpipe quick disconnect probably gives about 99000 btus at its best.

    I used a digital manometer at the far burner grill orifice and found the pressure to be 6.20" water column with that one burner opened but not lit.
    With all
    burners open but not lit, the pressure dropped to 5.2" water column. I then turned on the kitchen oven (which is rated at 145000 btus) on high and turned opened a shower and a faucet to hot that sources from a tankless hot water heater (noritz 250,000 btus). And the pressure dropped to 4.25" water column.

    The grill specs states 4" water column. The grill does get hot but it takes a good 25-30+ minutes and longer in colder weather. The tech says it should only take 15 min max. The grill's flame looks good with height with one burner lit. With all burners lit on the grill I noticed a very slight reduction in height. At the very least, one burner (25000 btu) is at least adequately supplied.

    Questions I have:

    I used the tracpipe chart for 0.5" drop. Is that the correct chart to use? The other charts give larger btu ratings

    If the digital manometer is showing at least 4" water column pressure at the grill orifice (burner) with and without other appliances lit, am I then getting the max input to the grill that a 1/2" csst trac pipe will supply? Or is the chart at the proper length the btu supply to use?

    Am I undersized in using the gas supply 1/2" csst?

    If the 1/2" underground csst is undersized (which seems to be the case), would changing the 3/4" csst run inside the house to a 1" csst or black pipe and leaving the 1/2" underground csst make a difference?

    If I do have to repipe, would it be just the underground 1/2" or also the 3/4" csst run inside?

    I want to keep the grill but would hate to lift up the pavers on this patio to recipe.

    A licensed plumber ran the yellow pipe during the patio install and stated ' this pipe should give you plenty of gas', however I'd greatly appreciate advice/opinions. Thanks in advance.
  2. Hammerlane

    Hammerlane Member

    Oct 22, 2011
    Is there anyway where the 3/4" CSST joins to the 1/2" CSST that you could eliminate the 1/2" CSST and run a "temporary" 3/4" line to the grill and see how the grill functions?
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  4. WorthFlorida

    WorthFlorida USCG escorting cruise ship leaving Port Everglades

    Oct 28, 2009
    Orlando, Florida
    The grill spec is probably the minimum WC to get satisfactory performance, not 90K worth. Other than the preheat time, using all burners at once on high for cooking is usually not the rule. If having the kitchen oven on at the same time as the gas grill is possible, but all things will still get plenty hot. If the pressure is too low and you get flame out, then that is serious where the pipe has to be enlarge. Count the number of times you'll use the grill and duration, it may not be worth it to tear apart your patio.
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