Partly. A standard home inspection looks at the gas piping it can see, the main gas shutoff, and the gas water heater and its vent. It does not pressure test the lines, check buried yard lines, or confirm code compliance. For proof the whole system is leak-free, add a separate gas line inspection with a pressure test.
What does a home inspector check on the gas system?
A home inspector checks the parts of the gas system that are visible and accessible. Arizona certifies home inspectors under state law, which requires an approved exam, a course of study, and insurance or a bond. Two widely used national standards spell out the gas items.
The InterNACHI Standards of Practice say the inspector shall inspect "the main fuel supply shut-off valve" and "the water heating equipment, including the energy source, venting connections," and shall describe "the location of the main fuel supply shut-off valve." The ASHI Standard of Practice says the inspector shall inspect "Fuel storage and fuel distribution systems" and "Vent systems, flues, and chimneys," and describe the "Location of main water and fuel shut-off valves."
In a typical Phoenix house, that usually means:
- Visible gas piping in the garage, laundry, water heater closet, and at the meter.
- The main gas shutoff location, noted in the report.
- The gas water heater, including its vent connection and relief valve.
- The furnace, if gas fired, as part of the heating section.
- Visible defects the inspector observes and judges material, which InterNACHI defines as issues that could significantly affect value or pose "an unreasonable risk to people."
What does a home inspection leave out?
A home inspection leaves out anything hidden, and anything that takes testing tools. InterNACHI's standard describes the job as "a non-invasive, visual examination of the accessible areas" and says plainly: "An inspection will not identify concealed or latent defects." It also says the inspection "is based on the observations made on the date of the inspection, and not a prediction of future conditions." A clean report at closing says nothing about next year.
Here is what the standards exclude, item by item:
| Gas item | Covered by a standard home inspection? |
|---|---|
| Visible gas piping and supports | Yes |
| Main gas shutoff location | Yes, reported |
| Gas water heater, energy source, and vent | Yes |
| Pressure test of the gas piping | No |
| Underground or concealed gas lines | No. InterNACHI excludes "underground or concealed fuel supply systems" |
| Operating gas shutoff valves | No. Not required to operate "any shut-off valves or manual stop valves" |
| Lighting pilots | No. Not required to "light or ignite pilot flames" |
| Gas detector sweep | No. Not required to operate "gas detectors or similar equipment" |
| Code compliance or pipe sizing | No. Not required to determine "compliance with codes or regulations" or "the size, capacity, BTU" |
| Combustion air adequacy | No, under the ASHI standard |
An inspector can offer more than the standard requires, so ask what yours includes before you rely on it.
Why do buried gas lines matter when buying a house?
Buried gas lines matter because the buyer inherits them. Southwest Gas owns the piping up to and including the meter. Everything after it, including a line from a meter at the property line to the house and lines to a pool heater or barbecue, belongs to the owner. The utility's brochure tells owners to "Periodically inspect your lines for leaks and/or corrosion."
Federal pipeline rules back that up. Gas utilities that do not maintain customers' buried piping must tell customers so in writing, and the notice has to say that unmaintained buried piping "may be subject to the potential hazards of corrosion and leakage" and should be "Periodically inspected for leaks" and, if metallic, for corrosion.
A standard home inspection does not look at any of that. On an older property with a long yard line, a pool heater line, or an outdoor kitchen, those buried runs are the part most worth a separate check.
When should you add a separate gas line inspection?
Add one when the house has gas you cannot see, or when anyone involved needs written proof. A gas line inspection by a licensed plumber goes past the visual check. It usually includes a pressure test: the system is capped, pumped up with air or nitrogen, and watched on a gauge. Under the fuel gas code Phoenix uses, that means at least 1.5 times the working pressure and never less than 3 psig, held at least 10 minutes in a single-family home.
Good reasons to add one before closing:
- The gas has been off. In Phoenix, a meter locked at a vacant house with no piping changes is cleared by Southwest Gas, and the utility runs its own leak check at turn-on. Finding a problem before the meter is unlocked beats finding it on move-in day.
- Long or old buried lines, especially to a detached garage, pool heater, or outdoor kitchen.
- The inspector noted a gas defect, like a corroded section, a missing shutoff at an appliance, or an old brass connector.
- Unpermitted work is suspected, like a gas line added to a patio or a garage conversion with a new appliance.
- You plan to add load, like a pool heater or tankless water heater, and want to know whether the existing piping can carry it.
What should you ask about the gas system before closing?
Ask the questions a visual inspection cannot answer. A few minutes with the seller's disclosure, the inspector, and the listing agent can tell you where to look.
- Was any gas line added or moved? In Phoenix, any new gas piping or change to existing piping needs a city permit, inspection, and gas clearance. A patio grill line or a new range line with no permit on record is worth testing.
- Where do the buried lines run? Southwest Gas warns that customer buried piping can't be located by calling 811, so a sketch or photos from the seller are the best map you will get.
- How old are the appliance connectors? Southwest Gas says some older brass flexible connectors can separate and leak, and that uncoated brass ones should be replaced with stainless steel or plastic-coated connectors.
- Does each appliance have its own shutoff? The fuel gas code calls for a shutoff valve in the same room as the appliance and within 6 feet of it.
None of these answers replaces a test. They tell you whether a test is worth ordering. That's the point.
If you ever smell gas during a showing or an inspection, stop. Get out, and call 911 and Southwest Gas at 877-860-6020 from outside.
HQ Plumbing & Air does gas leak inspection and certification for homes and businesses across the Phoenix area, with a written certification letter when the system passes. We work on natural gas systems only, and you get the price up front before any work starts.
The home inspector looks. The gas inspection tests. On an older house, you want both.