What is a gas leak inspection and certification?

A gas leak inspection checks every part of the gas system you own, from the meter outlet to each appliance valve, and proves it holds gas without leaking. Southwest Gas owns the piping up to and including the meter. Everything after the meter, including buried lines to the house, a grill, or a pool heater, belongs to the property owner, and the utility tells customers to have those lines inspected and repaired when needed.

A proper inspection covers:

• The visible piping. Black iron, CSST, and copper runs get checked for corrosion, damage, missing supports, and loose or unapproved fittings.
• Appliance connections. The shutoff valve and flexible connector at the water heater, range, dryer, furnace, and any outdoor appliance. Old uncoated brass connectors are a known hazard, and Southwest Gas says they should be replaced with stainless steel or plastic-coated connectors.
• A pressure test. The line is capped, filled with air or nitrogen to a set pressure, and watched on a gauge. If the pressure holds, the piping is tight. If it drops, there is a leak somewhere.
• Leak pinpointing. When a test fails, the leak is found with a combustible gas detector or a noncorrosive leak detection fluid, repaired, and retested.

Under the fuel gas code Phoenix uses, the minimum test pressure is 1.5 times the working pressure, and never less than 3 psig, held for at least 10 minutes in a single-family home. Our page on how a gas line pressure test works walks through the numbers step by step.

In Arizona, a "gas leak certification" is not a state license or a single official form. It is written proof, from a qualified person, that your gas system passed inspection and is safe to put gas into. It usually shows up in one of three ways.

1. The Southwest Gas turn-on check. Southwest Gas's Arizona tariff says the customer must provide "a leak tight system for receiving gas," and the utility performs a leak check when it turns gas on. The same rule goes further: "The Utility may also refuse service until a certificate executed by an authorized public official or licensed plumber is issued." That one sentence is why so many people end up searching for a gas leak certification. The utility can ask for it before it restores service.

2. City inspection and gas clearance. For permitted work in Phoenix, a city inspector checks the piping and the test. Once it passes, the city issues a gas clearance, which is the city's release that lets Southwest Gas set the meter or turn it back on. Other Valley cities run their own permit and inspection offices, so the paperwork name can differ outside Phoenix.

3. A licensed plumber's written certificate or letter. When no permit is involved, a licensed plumber can inspect, test, and put the results in writing. This is the kind of document a landlord, property manager, buyer, or insurer may ask for. It should name the property, the date, what was tested, the test pressure and how long it held, any repairs made, and who did the work.

The certificate proves the system was tight on the day it was tested. It is not a lifetime guarantee, which is why a new owner, a new tenant, or a restaurant opening can call for a fresh one.

You need one whenever gas is being restored after a problem, whenever the piping is changed, or whenever someone with authority over the property asks for proof. The City of Phoenix, Southwest Gas, and the Arizona Corporation Commission put together a table that settles most cases for existing buildings.

The row that trips people up most is the leak row. If Southwest Gas found a leak on your side of the meter and locked it, a phone call will not get gas back on. The piping has to be repaired under a permit, inspected, and cleared by the city first. Our guide to what a Southwest Gas red tag means covers that restore process in order.

Other common triggers for a plumber's written certificate:

• Buying or selling a home, especially an older one where the meter sits out by the property line and a long buried yard line belongs to the owner.
• Landlords and property managers turning over a unit or restoring gas after a vacancy.
• Restaurants and commercial kitchens opening, changing hands, or answering a city or county health department's request for proof.
• After a gas smell or a failed inspection, to document that the fix held.

The inspection follows the same order every time, because gas work has no shortcuts. Here is the sequence a licensed plumber runs.

1. 1Shut off and isolate. Gas is shut off at a building shutoff valve. Appliances that cannot take the test pressure are disconnected and their outlets capped, as the code requires.
2. 2Look over the whole system. The plumber walks the piping from the meter to each appliance, checking fittings, supports, connectors, valve locations, and CSST bonding where CSST is present.
3. 3Pressure test. A gauge goes on, the line is pumped to the test pressure with air or nitrogen (never oxygen), and the pressure is watched for the full test time. The code treats any drop on the gauge as a leak unless it can be readily traced to some other cause.
4. 4Find and fix. If the needle falls, the plumber traces the leak with a gas detector or leak detection fluid, repairs or replaces that section, and runs the test again.
5. 5Document. The results, repairs, and test details go into the written certificate.
6. 6Restore and relight. When gas is turned back on, the code requires another leak check immediately, and appliances are not put back in service until that check, a purge of air from the lines, and a check of each appliance connection are done. If Southwest Gas locked the meter, only the utility turns it back on, and it will run its own leak check too.

When a system fails, the plumber checks threaded joints, old appliance connectors, valves, and buried lines that have corroded or been hit by digging.

Call a licensed plumber who works on natural gas, and tell them who asked for the certificate and why. That detail changes the job. A lender or buyer may only want a written test result, while a meter locked for a leak needs a permit, a repair, a city inspection, and a city clearance before Southwest Gas comes back.

Before you book, ask for three things:

• The exact document the requester wants. Ask Southwest Gas, the city, your landlord, or the inspector what form they will accept, so you are not paying for a second visit.
• A licensed contractor who does gas work. Our page on who can install a gas line in Arizona covers licensing and permits.
• The test details in writing: test pressure, how long it held, and any repairs.

HQ Plumbing & Air does gas leak inspection and certification for natural gas systems in homes and businesses across the Phoenix area, with a written certification letter when the system passes. We work on natural gas only, not RV or portable propane systems. If we find a leak, we tell you what failed and the repair price up front, before any work starts.

One safety note before any of this: if you smell gas, leave first and inspect later. Get everyone out, leave the door open behind you, and do not flip switches, use appliance controls, or start a car in the garage. From a safe spot outside, call 911 and Southwest Gas at 877-860-6020. A certification is for proving a system is safe after the fact. It is never a reason to stay in a building that smells like gas. Our page on why your house smells like gas or rotten eggs covers the smell itself.

The short version: the inspection is the test, the certificate is the proof, and in Arizona the proof is what gets your gas turned back on.