To pass a California gas line pressure test, isolate the piping, pressurize it with air or an inert gas to at least 1.5 times the working pressure (with a 3 psi floor under the 2025 California Plumbing Code), and hold that pressure with zero gauge movement for the duration your local building department requires. Most jurisdictions apply a stricter practical standard than the code minimum: 10 psi held for 15 minutes on a low-range gauge is the common benchmark, and the system has to stay pressurized while an inspector verifies the hold before any utility will turn on your gas.
When a Pressure Test Is Required
CPC Section 1213.3 triggers a test in three situations: new gas piping, repairs or additions to existing piping, and restoration of service after an extended shutoff. New branches off an existing system get tested separately, and the tie-in points between old and new piping have to be leak-checked by an approved method.
Alterations count. Relocating a meter, extending a line for a new appliance, or replacing a corroded section all require the altered portion to pass a test before gas flows. Tightening a single fitting may not, but the connection still gets inspected and leak-checked.
If gas service has been off for an extended period, your utility will require proof the system is still sound. SoCalGas will not establish service until the piping “has been released by the local inspection agency.”1SoCalGas. Natural Gas Service Guidebook PG&E follows the same process. Dormant lines can develop corrosion, joint failures, or settling damage that a pressure test exposes before live gas is introduced.
Earthquakes and fires trigger testing too. When a seismic shutoff valve trips, the system should be pressure-tested before the valve is reset and service restored.2City of Palo Alto. Whole House Gas Test Fire heat can weaken fittings and warp pipe that still looks sound.
The Pressure and Duration You Need to Hit
CPC Section 1213.3 sets the baseline at 1.5 times the proposed maximum working pressure, with a floor of 3 psi, held for at least 10 minutes with no perceptible drop. For piping that will carry gas above 125 psi, the code caps the test pressure so the pipe isn’t stressed beyond 50 percent of its minimum yield strength.
Residential gas in California typically operates under 0.5 psi, so the 1.5x formula produces a number well below the 3 psi floor. That’s why local jurisdictions set stricter standards. Palo Alto requires 10 psi on a 15 psi gauge held for 15 minutes, and that figure is the de facto standard across much of the state.2City of Palo Alto. Whole House Gas Test Call your building department before you start and get the exact pressure and time they expect, because that’s the number the inspector will enforce.
Test medium is limited by CPC Section 1213.1.6 to air, nitrogen, carbon dioxide, or another inert gas. Oxygen is prohibited because it supports combustion. Compressed air from a portable compressor or a hand pump handles most residential tests. Nitrogen is cleaner and drier if you want to avoid introducing moisture.
Preparing the System
Shut the main supply valve and disconnect every appliance or cap the open lines with threaded plugs. The code specifically requires that appliances rated for operating pressures below the test pressure be disconnected and capped. A water heater or furnace left connected during a 10 psi test can damage internal valves and regulators built for pressures under 1 psi.
Leave every joint exposed. The inspector has to be able to see welds, threaded connections, and fittings. If you’ve already backfilled a trench or closed a wall, you may have to open it back up. Schedule the test before you cover anything.
Use the right gauge. For a 10 psi test, a 0–15 psi or 0–30 psi gauge lets you see small changes. A 0–100 psi gauge makes a slow leak nearly invisible at the low end of the scale. Connect a test assembly with its own shut-off valve, pressurize slowly to the target, close the shut-off, and isolate the pressure source before you start timing.
Running the Test and Chasing Leaks
Watch the needle for the required duration. Any downward movement is a failure, even one that’s barely perceptible over 15 minutes. If the pressure drops, the leak is somewhere in the system or in the test assembly itself.
Brush a non-corrosive leak-detection solution or soapy water onto every joint and connection while the system is pressurized. Bubbles form where gas is escaping. Work methodically from one end to the other so nothing gets skipped.
Threaded connections fail most often. Pipe dope or Teflon tape applied too thinly, cross-threaded fittings, or debris in the threads produce slow leaks that only show up on a gauge. Remake the connection, then retest the whole system from scratch. Partial retests aren’t acceptable for the initial inspection.
The Inspection and the Green Tag
Once the system holds, request an inspection through your building department’s portal or by phone. The piping must still be pressurized when the inspector arrives, so maintain pressure from the original test or re-pressurize just before the appointment. Have your permit number ready and make sure someone is on site.
The inspector checks more than the gauge. They verify that the gauge is appropriately sized and calibrated, that all joints are visible, that the pipe materials are approved for gas (black iron, corrugated stainless steel tubing, or other listed materials), and that the installation generally conforms to code. Corrugated stainless steel tubing has additional bonding requirements that get checked as well.
A passing system gets a “green tag” or green sticker, usually placed at the gas stub-out or meter.3City of Palo Alto. Gas Meter Release That tag is the formal sign-off that clears the utility to turn on gas. If the system fails, the inspector lists the deficiencies, and you’ll schedule a re-inspection after repairs.
Getting the Gas Turned On
After the green tag, the building department notifies the utility that the system has been cleared. SoCalGas requires this “houseline approval” from the local governing agency before scheduling a meter set or turn-on.1SoCalGas. Natural Gas Service Guidebook PG&E and SDG&E follow the same process. Keep your own copy of the inspection approval in case the electronic notification is delayed.
Expect a wait. SoCalGas reports typical meter installation and turn-on times of 7 to 14 business days after houseline clearance. During heating season (roughly November through February), that can stretch past 20 business days.1SoCalGas. Natural Gas Service Guidebook Plan around that if you’re doing work in winter.
When the technician arrives, they open the valve at the meter, check for leaks at the meter connection, and may help relight pilot lights.
Can a Homeowner Do the Work
Yes, within limits. California Business and Professions Code Section 7044 lets a homeowner perform work on their own property without a contractor’s license, provided they do the work themselves rather than through unlicensed helpers, the property isn’t being improved for immediate sale, and the required permits are pulled.4California Legislative Information. California Business and Professions Code 7044 The work still has to pass the same inspection a licensed plumber’s work would.
If you hire out the work, it falls under the C-36 Plumbing Contractor classification issued by the Contractors State License Board. The C-36 covers gas piping from the owner’s side of the utility meter to the building, appliance connections, flues, and earthquake shutoff valves.5CSLB. C-36 – Plumbing Contractor – Licensing Classifications Detail Verify an active C-36 license on the CSLB website before anyone starts.
What Skipping the Permit Costs You
Any gas piping installation, alteration, or repair requires a plumbing permit from your local building department, pulled before work begins. Most California jurisdictions charge double the original permit fee as a penalty when unpermitted work is discovered, and investigation fees and code enforcement costs can push the total well past the cost of doing it right the first time.
Insurance is the bigger exposure. A homeowner’s policy may deny a claim tied to a gas leak or fire if the work was never permitted or inspected, on the reasoning that the installation didn’t meet code. Appliance manufacturers often require permitted installation as a condition of warranty coverage. For contractors, performing permit-required work without one is grounds for CSLB discipline, including suspension.
The pressure test exists because gas leaks kill people. The permit and inspection are what make sure the test actually happened and that someone with no stake in the project verified it.