If you suspect a leak, leave the building first, then call 911 and Southwest Gas at 877-860-6020 before you investigate. Signs include a rotten-egg odor, a hissing sound, and bubbles when you brush soapy water on a line. A licensed gas fitter finds, repairs, and pressure-tests the line.
Get out and call first, before you investigate
The first rule of any suspected gas leak is that you do not investigate while you are still inside a building that may be filling with gas. Natural gas is flammable, and a small spark can set off what has built up in a room. Leave on foot, take other people and pets with you, and prop a door open so some gas can escape as you exit.
On your way out, do not touch anything that can make a spark. That means light switches, thermostats, appliance controls, lighters or matches, the garage door opener, and vehicle ignitions. Even a switch you flip out of habit counts. The goal is to add zero sources of ignition while you move to safety.
Once you are outside and a safe distance away, call 911 and then Southwest Gas at 877-860-6020. Southwest Gas tells customers to report from a safe place, day or night, and the line is staffed around the clock. The utility can shut off service at the meter and check the area with professional instruments. Do not go back inside until 911, the gas company, or the fire department tells you it is safe.
How to detect a gas leak
The most common warning sign is smell. Natural gas has no odor on its own, so the gas company adds a chemical called mercaptan that smells like rotten eggs or sulfur. That distinct stink is the signal most people notice first. If you catch it indoors and it does not fade, treat it as a leak and follow the safety steps above.
Sound and sight give you more clues. A leak under pressure can make a hissing or even a roaring noise near a line, a fitting, or an appliance connection. Outdoors, gas escaping from a buried line can blow dirt around, send bubbles up through standing water, or kill nearby plants, so watch for dead or dying vegetation over the path of a line.
For an exposed line or a fitting you can reach safely from outside the danger area, a simple soapy-water test works. Brush or spray a mix of dish soap and water onto the pipe and joints. Escaping gas pushes through the film and makes steady bubbles at the leak point. A plug-in or battery gas detector adds another layer, since it can alarm on gas your nose has stopped registering. Mount a detector low if you are checking for heavier-than-air fuels and near the ceiling for natural gas, which is lighter than air and rises.
It helps to know where leaks tend to start. The most common spots are threaded joints and fittings, the flexible connector behind an appliance, valves that get turned often, and any buried run that has been disturbed by digging or settling soil. Appliances that have been bumped, moved, or recently serviced are worth a closer look. None of this changes the order of steps: if the smell is strong or you are unsure, you leave and call first, and you save the closer inspection for a safe line or a trained responder.
That last point matters because smell is not reliable on its own. The federal pipeline safety agency, PHMSA, warns that odorant can fade. As its guidance states, "Some conditions can cause the odor to fade so that it may not be detectable." Odor can weaken when gas passes through soil, rust, or certain pipe materials, and a person can also lose the ability to smell it after a short exposure. So do not rely on smell alone. If your senses, a detector, or a bubble test point to a leak, act on it.
How a licensed gas line repair works
Repair starts with finding the exact leak, not guessing at it. A licensed gas fitter confirms the location with a calibrated gas detector and a soap test, working from the meter through the affected line. Pinpointing the spot first keeps the fix targeted and avoids opening up pipe that is fine.
Once the leak is located, the fitter repairs or replaces the affected section. A loose or damaged fitting may be remade, while a corroded or cracked length of pipe is cut out and a new section is installed. The repair has to match the existing pipe type, whether that is rigid black iron or flexible corrugated stainless steel tubing (CSST), and it has to meet code for joints, supports, and protection.
After the work, the line is pressure-tested before gas goes back on. Under the 2018 International Fuel Gas Code that Phoenix uses, the test pressure must be at least 1.5 times the working pressure and not less than 3 psig, which is why crews call it the 3 lb test at final. The line holds that pressure for a set time so any drop reveals a remaining leak. A permit is required for gas piping work in Phoenix, and the repaired line must pass inspection before the utility restores service. Plan for the gas to stay off until that sign-off happens.
The contractor doing the work must be ROC-licensed for the job. The Arizona Registrar of Contractors lists the classifications that cover gas piping, and a residential plumbing license includes water and gas piping. Hiring a licensed gas fitter is what ties the repair to the permit, the pressure test, and the inspection that let your service come back safely. For who is allowed to do this work, see our guide on the gas line permit and who can install gas piping in Arizona.
What drives the cost of a gas line repair
Repair pricing turns on a handful of factors, and the biggest is usually where the leak is and how easy it is to reach. A loose fitting on an exposed line in an open space is a quick fix. A leak behind a wall, under a slab, or in a tight crawl space takes longer to access and costs more.
Buried versus exposed pipe is the next driver. A buried line that feeds a pool heater, an outdoor kitchen, or a fire pit may need trenching to expose it before any repair starts, and the dirt has to go back afterward. The length of pipe that has to be replaced and the material used both add up too, since more pipe and more fittings mean more labor and parts.
The required paperwork adds known steps to the bill. The permit and the inspection are part of doing the job to code, and if a test fails and the line needs a re-inspection, that adds time. We do not quote a flat figure here because the real number depends on the factors above, and an honest estimate comes only after a fitter sees the line. If your concern started with a sulfur smell rather than a known leak, our page on why a house smells like gas or rotten eggs walks through what that odor can mean.