Commercial Gas Line Pressure Testing

A pressure test isn't a yearly checkup. It's required at specific moments, and the city or the gas company is usually the one asking:

• New piping before it is covered or put in service, which is every restaurant build-out and every new branch.
• Repairs and alterations to existing piping, at least for the part that was opened up.
• Getting gas back on after Southwest Gas locked the meter for a leak on your side, which in Phoenix means a permit, inspection and city clearance.
• A clearance with no new work in unincorporated Maricopa County, which still needs a permit and a pressure test.
• When Southwest Gas asks for proof. Its Arizona tariff lets it refuse service until a certificate is issued by an authorized public official or a licensed plumber.

If what you need is a written inspection report or a certification letter for a health department, landlord or insurer, that's our gas leak inspection and certification service. This page is the test that goes with permits and clearances.

We isolate the piping, take the appliances off it, pressurize with air or nitrogen and leave a gauge on it.

Prep. Section 406.3.3 says appliances designed for less than the test pressure are disconnected and their outlets capped. On a commercial cooking line that's nearly everything, since appliance controls and connectors are built for low pressure. Joints stay exposed so a leak can be found.

Medium. Section 406.2 allows air, nitrogen, carbon dioxide or an inert gas. Oxygen is never used.

Gauge. Section 406.4 calls for a manometer or a gauge calibrated to show a loss from leakage. A mechanical gauge's full scale can be no more than five times the test pressure, so a 3 psig test doesn't go on a 100 psi gauge. Mesa tightens that to twice the test pressure with 0.1 psi markings.

Hold. The base code sets half an hour per 500 cubic feet of pipe volume. Gilbert sets a 15-minute minimum at 10 psi.

Read. Section 406.5 is strict: any drop is a leak unless something else clearly explains it, such as a big temperature swing on a rooftop run in July. We'd rather find the leak than argue the gauge.

The number on the gauge depends on where the building is. These are the rules we've checked against each city's code text:

Chandler's 10-minute figure comes from its residential homeowner permit manual, which says most systems test at 3 psig unless they're above 2 psi. For a commercial job, confirm the hold time with Chandler's inspector. For every city on one page, see our gas pressure test rules by city.

The city inspector does. In Phoenix it's commercial inspection 235, gas piping. Maricopa County's inspection guide says interior gas piping should be on its required pressure test when the inspector arrives at rough-in, and Gilbert inspects twice: before the piping is concealed and again after, before appliances go on. So the test isn't a five-minute check we run and remove. It stays on, gauge visible, until the inspector reads it.

After the inspection passes, the city sends the clearance to Southwest Gas. When gas is turned on, Section 406.6.3 requires an immediate leak check, and Southwest Gas runs its own at turn-on. Our page on how a gas line pressure test works covers the same steps for a home.

A drop means finding the leak. We work along the exposed joints with a combustible gas detector and leak-detecting fluid, the methods Section 406.5.1 names, repair or replace what's leaking, and put the test back on. Section 406.5.2 requires the retest. On a failed test of old piping, sometimes the honest answer is that the run needs replacing, and we'll tell you that with a price before doing it. See commercial gas line repair.

No, and don't try. Over-pressurizing a line with appliances still connected can damage their controls, and a test that hasn't been witnessed doesn't satisfy the city or Southwest Gas. A property manager can do one useful thing in advance: confirm the permit number and inspection window, and make sure the meter area and the piping are accessible on test day.

We isolate and cap the appliances, run the test at the pressure your city requires, keep it on for the inspection, fix anything that drops, and get the clearance to Southwest Gas. When gas goes back on, we leak-check, purge and relight. We're licensed and insured, with free estimates and an upfront price. Related: commercial gas line service, restaurant gas line installation, property management plumbing and restaurant plumbing.