Natural Gas Line to a Fire Pit in Seattle or Portland: Permits, Pipe Size and Burial

Not legal or electrical advice. This guide summarizes published manuals, codes and agency pages as of the date above. Rules change and vary by jurisdiction. Confirm your plans with a licensed electrician or contractor and your local building department before you buy or install.

Key facts

Seattle: gas piping permits are issued by Public Health Seattle and King County (PHSKC), which also covers Clyde Hill and unincorporated King County. Other King County cities issue their own.
Seattle homeowners can pull permit type 21, Natural Gas by Homeowner, for their own work. Anyone piping on property they do not own needs a Seattle Gas Piping Mechanic License.
Portland: a residential mechanical permit is required for any indoor or outdoor gas piping between the meter and the appliances, even with no building permit. Only the recorded owner (not an LLC) may do their own work.
Burial: at least 12 inches of cover, or 8 inches for a line to a single outdoor appliance where approved (2021 IRC G2415.12, IFGC 404.12).
811: two to ten full business days before digging in both states.

Seattle and King County: the permit

Seattle's building department enforces the Fuel Gas Code, but it does not issue gas piping permits. Its Fuel Gas Code page sends you to Public Health Seattle and King County. PHSKC says a permit is required whenever gas piping is installed, relocated or changed, and its jurisdiction covers Seattle, Clyde Hill and unincorporated King County. If you live in Bellevue, Kirkland, Redmond or another King County city, call that city's permit desk instead.

PHSKC's permit types list two routes for a house:

Type 21, Natural Gas by Homeowner. For gas work done by the homeowner only, on their own home. State law (RCW 18.106.150) allows it.
Types 22a and 22b, Natural Gas Residential. For registered contractors.

PHSKC also notes that in Seattle anyone working on gas piping on property they do not own must hold a Seattle Gas Piping Mechanic License, and that it charges $40 when a permit is pulled for the wrong site. Every installation needs both a permit and an inspection.

Portland: the residential mechanical permit

Portland Permitting and Development says a residential mechanical permit is required to install, repair or alter gas piping, indoors or outdoors, from the meter to the appliances. You need it even when the project needs no building permit, so a fire pit on an existing patio still needs one.

Who can do the work: the recorded owner of the house, doing their own work (a property held by an LLC does not qualify), or a contractor with an Oregon CCB license.
How to apply: online through DevHub. The city says the application takes about 15 minutes and the permit is issued within 24 hours of payment.
Inspections: a rough-in inspection before the pipe is covered, then the final mechanical inspection (code 699).
Drawings: the city's residential guide asks for a to-scale drawing of pipe layout and sizes when you add four or more new gas outlets.
Fees: the city's mechanical permit form (revised July 2026) lists gas fuel piping at $25 for the first four outlets and $4.29 for each additional, a $167 minimum permit fee, and a 12 percent state surcharge. A single fire pit outlet would fall under the minimum. Confirm the total in DevHub, since fees change.

Sizing the pipe from the meter

The new fire pit adds load to every section of pipe it shares with your other gas appliances, not just the new leg. PHSKC's installing gas piping page gives the method and a chart for low pressure natural gas (0.5 psi or less, 0.5 inch water column drop):

Convert each appliance's BTU rating to cubic feet per hour (CFH) by dividing by 1,100.
Measure from the meter to the most remote outlet. Use that one length column for every section.
Size each section for the total CFH of all appliances it feeds.

Pipe size	30 ft	50 ft	70 ft	100 ft	125 ft
1/2 in	95	72	60	50	44
3/4 in	199	151	126	104	92
1 in	374	284	237	195	173
1-1/4 in	768	583	486	400	355

Capacity in CFH, selected columns from the PHSKC chart. PHSKC's typical demand figures include 40,000 BTU for a barbecue, 65,000 for a range, 80,000 for a fireplace gas log set and 50,000 for a 50 gallon water heater. Use the rating plate of your actual appliances.

Illustration (hypothetical house): a 3/4 inch main feeds a 50 gallon water heater (about 45 CFH) and a range (about 59 CFH), 104 CFH total. You add a 55,000 BTU fire pit burner (50 CFH), which brings the shared section to about 155 CFH and makes the longest run 70 feet. At 70 feet, 3/4 inch pipe carries only 126 CFH, so that shared section would have to go up to 1 inch (237 CFH). The dedicated 1/2 inch leg to the pit carries 60 CFH at 70 feet, which covers the 50 CFH burner. This is why a fire pit at the back of a long yard can mean replacing pipe near the meter.

Also confirm the fire pit you buy is configured for natural gas. Propane and natural gas burners are set up differently, so use the maker's natural gas version or its own conversion instructions.

Burial, pipe material and tracer wire

The ICC's CodeNotes on underground gas piping summarizes the 2021 IRC and IFGC rules (Seattle adopted the 2021 IFGC with amendments; ask your inspector which edition applies to your permit):

At least 12 inches of cover. A line to an individual outdoor appliance, like a fire pit or grill, can be 8 inches deep where approved and not exposed to physical damage.
Plastic (polyethylene) gas pipe is allowed underground, including under outdoor patios, walkways and driveways at code depth. It must not run above ground; it comes up through an anodeless riser.
Plastic pipe needs a yellow insulated copper tracer wire, at least 18 AWG and rated for direct burial, reachable or ending above ground at each end, so the line can be located later.
Galvanizing alone is not acceptable corrosion protection for buried metal pipe. Underground piping may not pass through a foundation wall below grade.

PHSKC adds that black iron and CSST are the common materials, that CSST installers need the maker's certification, and that every appliance needs its own shutoff valve.

Testing and inspection

PHSKC's guidance for an air test: at least 1.5 times the working pressure and never less than 3 psi, held for at least 10 minutes, on a gauge whose top of scale is no more than 5 times the test pressure (a 3 psi test needs a gauge that reads to 15 psi or less). Leave the piping exposed until it passes inspection, so do not backfill the trench first. Check joints with soapy water, never a flame.

Call 811 before you trench

Washington: mark the dig area in white, then notify 811 at least two and no more than ten full business days before digging (the notice day, weekends and holidays do not count). Since January 1, 2026, you may not dig until every utility operator has responded. Lines you own privately, such as power or gas to a detached garage, may not be marked, so you may need a private locator.
Oregon: the same two to ten full business day window. The only exemption is for an owner or tenant digging less than 12 inches deep on their own property outside an easement. A 12 inch gas trench is not under 12 inches, so call 811 (or 800-332-2344).

Where to put the pit, and when you can use it

Before you pick the outlet location, check clearances in how far a fire pit must be from the house. A gas line also matters during burn bans: see Washington burn bans and fire pits, Oregon fire pit restrictions and gas fire pits during summer burn bans. If a gas line is not practical, compare running costs in how long a propane tank lasts in a fire pit.

Sources

Rules and fees as published by each agency and checked on October 23, 2026. The sizing illustration is our own arithmetic using the PHSKC chart. Codes, fees and agency processes change, and your inspector has the final say. This guide is not legal or engineering advice and does not replace a licensed gas fitter.

Related guides

Frequently asked questions

Do I need a permit to run a natural gas line to a fire pit in Seattle?

Yes. Public Health Seattle and King County says a permit is required whenever gas piping is installed, relocated or changed. In Seattle, gas piping permits come from Public Health Seattle and King County, not from the Seattle Department of Construction and Inspections. Public Health also covers Clyde Hill and unincorporated King County. Other King County cities issue their own permits.

Can a homeowner run the gas line themselves in Seattle?

A homeowner can get a homeowner gas piping permit to do the work on their own home. Public Health Seattle and King County lists it as permit type 21, Natural Gas by Homeowner, for work done by the homeowner only. Anyone piping gas on property they do not own needs a Seattle Gas Piping Mechanic License, and contractors use the residential permit types.

Do I need a permit for an outdoor gas line in Portland?

Yes. Portland Permitting and Development requires a residential mechanical permit to install, repair or alter gas piping, indoors or outdoors, between the meter and the appliances. You need it even when the project needs no building permit. Owners can do their own work only if they are the recorded owner (an LLC does not count). Contractors need an Oregon CCB license.

How deep does a gas line to a fire pit have to be buried?

Under the 2021 International Residential Code and International Fuel Gas Code, underground gas piping needs at least 12 inches of cover. A line serving an individual outdoor appliance can be 8 inches deep where the code official approves it and it is not exposed to damage. Plastic pipe needs a yellow insulated copper tracer wire of at least 18 AWG. Your local code and inspector have the final say.

Do I have to call 811 before digging a gas trench?

In practice, yes. Washington and Oregon both require a locate request at least two and no more than ten full business days before you dig. Since January 1, 2026, Washington excavators may not dig until every utility operator has responded. Oregon only exempts digging under 12 inches deep on your own property outside an easement, and a 12 inch gas trench does not fit that exemption.

What size gas pipe does a fire pit need?

Divide the burner's BTU rating by 1,100 to get cubic feet per hour, then size each section of pipe for the total load flowing through it at the length from the meter to the farthest outlet. The Public Health Seattle and King County chart shows, for example, that 1/2 inch pipe carries 60 cubic feet per hour at 70 feet and 3/4 inch carries 126.

Keep reading

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Running a natural gas line to a backyard fire pit in Seattle or Portland