How do you run a gas line to a fire pit?

Start with the burner's BTU rating. It is on the burner's label and in its manual, and fire pit burners cover a wide range. Warming Trends, a burner maker, sells its systems from 60,000 to about 300,000 BTU an hour and matches the parts at the pit to the size:

Those are the fittings at the pit, not the size of the pipe from the house. The supply pipe is sized with the fuel gas code's tables, which Phoenix uses: the total BTU on that branch, the length of the run from the meter, and the allowed pressure drop. Natural gas carries about 1,000 BTU per cubic foot, so a 200,000 BTU fire pit burns about 200 cubic feet of gas an hour, as much as a large tankless water heater. On a long run across a yard, a 1/2 inch pipe that looks fine can starve a big burner. Our page on the longest length method shows how those tables are read.

### Is a 1/2 inch gas line big enough for a fire pit?

For a small burner close to a well sized supply, often yes. The Warming Trends kits put 1/2 inch parts on burners up to 120,000 BTU. A bigger burner, a long run, or a branch shared with a pool heater or a grill can need 3/4 inch or more. The plumber also checks the gas pressure at the pit with the other appliances running.

• At the house: a tee into a section of gas pipe with enough capacity, or a new branch. Teeing into a small line that already feeds a dryer or range can starve both.
• Under the yard: coated steel or plastic gas pipe made for burial. The code allows plastic gas pipe outdoors and underground only, with an insulated copper tracer wire laid beside it so a locator can find it later.
• At the pit: a manual shutoff outside the burner. Warming Trends says "All appliances must have a gas shutoff located outside of the appliance to allow for emergency shutoff and maintenance." A key valve set through the side of the pit, or on a wall nearby, is the usual way. The code also wants an appliance's shutoff close by, within 6 feet.
• Inside the pit: the flex line from the valve to the burner, then the burner pan and fire media.

### Which related components complete the system?

Beyond the pipe, a finished gas fire pit has a key valve and key, the flex line, the burner, a plate or pan that holds it, fire rated media (glass, lava rock or a log set) and an ignition. Warming Trends recommends an ignition system on any burner over 300,000 BTU, and an electronic ignition needs an electrical shutoff, a wall switch or breaker, outside the pit. Some systems also carry a regulator (below).

### What supports the tray above the connection?

Not the gas parts. Warming Trends says the weight of the burner system "must not be supported by or rest upon the control valve/box." A plate or pan carries it, set on a ledge of blocks, bricks, L-brackets or metal collars, with a center support for round or square pans over 30 inches and rectangular ones over 40 inches. The space under the pan stays open: the manual says the lower cavity cannot be filled with gravel, crushed rock or concrete, and control boxes sit above grade with drainage so water does not reach them.

The short flex line between the key valve and the burner is where most fire pit problems start.

### How is hose diameter matched to burner demand?

Firepitsdirect, a fire pit parts seller, puts it plainly: "Diameter follows total connected load, not convenience." The burner's BTU rating sets the smallest bore the connection can have, which is why the Warming Trends kits step up from 1/2 inch to 3/4 inch to two lines as burners get bigger. Run length and fittings count too.

### What causes a gas line to whistle?

"Whistling is turbulence becoming audible," the same seller says: gas moving too fast for the passage carrying it. A larger bore lowers the speed for the same flow and the sound stops. Closing the valve partway to quiet it only starves the burner.

### How tight can a stainless flex line bend?

Only as tight as its maker allows. Every flexible line has a minimum bend radius published by its manufacturer, and bending it tighter crimps the corrugations and chokes the flow at the bend. Over time a tight bend can also crack the wall.

### How do flare fittings differ from NPT threads?

A flare fitting seals metal to metal on a machined cone face, held by the flare nut. A pipe thread (NPT) seals on tapered threads with sealant. They are not interchangeable, and forcing one onto the other ruins the seat, so the change is made with an adapter built for it. Warming Trends says to put thread sealant on male pipe threads only, and never on the flared end of a flare fitting.

### Is the flex line rated for enclosure or buried use?

Check the rating on the assembly itself. A line that is not explicitly rated for soil contact never goes in the ground. The run under the yard is gas pipe made for burial, and the flex line stays inside the pit where it can be reached.

### How does pressure regulation affect line performance?

The burner has a pressure window it must see at its inlet. Warming Trends lists 3.5 to 7.0 inches of water column for its natural gas match light burners and higher ranges for propane, and sells a natural gas regulator for burners up to 125,000 BTU. A pipe sized right from the meter is what keeps the pressure inside that window when the other appliances run.

The fuel gas code's general rule is 12 inches below grade. Lines that serve only an outdoor appliance such as a grill, an outdoor light or a fire pit may be 8 inches deep, but only where that is approved and the line is not likely to be damaged. Under a lawn you aerate or a bed you plant, deeper is the safer choice, and the inspector has the final word. Our guide to a natural gas line for a grill covers the same outdoor rules in more detail.

A pit built of block, stone or concrete around the burner needs vents. Warming Trends calls for at least one vent on two opposing sides, each at least 18 square inches (3 by 6 inches or larger), set in the mid to lower part of the enclosure. Its manual says venting lets heat "and/or residual fuel" escape, and that skipping it can lead to overheating or an explosion. Propane is heavier than air and settles low, which is why the vents go low. The same manual also asks for 36 inches of clearance to anything combustible beside the pit and 120 inches overhead.

Use the fuel the burner is built and listed for. Warming Trends warns not to use an alternative fuel. A natural gas burner runs off the house line and never needs a tank swap. A propane burner runs off a tank, and in Phoenix a propane system has its own rules: the Fire Code requires a Fire Department construction permit to install an LP-gas system, and Phoenix added small vapor service tanks at houses to that list. Our page on the Phoenix propane tank permit explains which tanks it covers, and natural gas vs propane compares the two fuels.

It depends on the job, so a plumber prices it after a look. What moves the price most:

• Distance and trenching: how far the pit sits from a gas pipe with spare capacity, and what is in the way (pavers, a pool deck, concrete).
• Burner size: a 250,000 BTU burner can need a bigger pipe all the way back toward the meter.
• What else is on the line: a pool heater or grill on the same branch changes the sizing.
• Permit and inspection: the city permit, the inspection, the pressure test and the gas clearance.

If a grill or a pool heater is in the plan, run one properly sized trench for all of them. Our page on the cost to add a gas line goes through the rest.

Yes. The City of Phoenix list of gas work lists "Any new gas piping installation" as needing a city permit, a city inspection and a city gas clearance. A fire pit line is new piping. Before it is covered, the new pipe is pressure tested. Warming Trends adds that the burner and its own shutoff must be disconnected from the line for any pressure test over 1/2 psi, so the test does not damage the burner's controls.

Once it is in, the line is yours. Southwest Gas owns the pipe up to and including the meter, and everything after it, fire pit lines included, is customer owned piping. Calling 811 before you dig does not mark customer buried piping, so keep a photo of the open trench with a tape measure in it. If you ever smell gas at the pit, close the key valve, move away and call Southwest Gas at 877-860-6020 from a safe spot.

HQ Plumbing & Air sizes and installs natural gas lines to fire pits, grills, patios and pool heaters across the Phoenix area, pressure tests them and takes them through the city permit, inspection and gas clearance. Call for a free estimate.