Gas line inspection in Bellevue: when you need one and what the plumber checks

When should you get a gas line inspection?

Before buying a home with gas appliances, after adding any new gas appliance, after a significant earthquake, when you smell gas intermittently without a clear source, or when the gas piping is black iron more than 30 years old.

Home purchase is the most important trigger. A standard home inspection includes a visual check of gas appliances but typically does not include a pressure test of the gas piping itself. A licensed plumber performing a dedicated gas line inspection pressure-tests the distribution system — if it holds pressure, the system is leak-free; if it drops, there is a leak somewhere that has to be found and repaired before anyone moves in.

Seismic events shake pipe connections and can damage or loosen fittings, particularly on older threaded black iron piping with many connections. Washington State sits on an active subduction zone; even moderate earthquakes in the Puget Sound region warrant a post-event inspection if you have gas appliances.

Intermittent gas smell — something that smells like rotten eggs occasionally but never triggers a clear emergency — is a classic sign of a small leak at a fitting rather than a major rupture. This warrants an inspection and pressure test, not repeated calls to PSE. Small leaks at fittings are common on aging black iron piping where the threaded joints have been through decades of thermal cycling.

What does a gas line inspection include?

A pressure test of the distribution system, visual inspection of all accessible piping and fittings, check of appliance shutoff valves and sediment traps, and CSST bonding verification where corrugated stainless steel tubing is present.

The pressure test is the core of the inspection. The plumber caps off the appliance connections, pressurizes the gas distribution lines with air or nitrogen to a standard test pressure, and holds for a set period. A drop in pressure indicates a leak. The test pinpoints the general location; the plumber then uses a combustible gas detector (a 'sniffer') to find the exact fitting or section.

Visual inspection covers the type of pipe material (black iron, copper, CSST), the condition of fittings and joints, the presence of sediment traps (drip legs) where required by code, and the condition of appliance shutoff valves. Valves that are corroded, stuck, or missing are flagged for replacement.

CSST bonding verification: corrugated stainless steel tubing (the flexible yellow-jacketed pipe common in post-2000 homes) requires arc-fault bonding per Washington State code. A bonding wire connects the CSST system to the electrical grounding system, protecting against lightning-induced puncture. Many older CSST installations predate the bonding requirement — an inspection confirms whether bonding is present and code-compliant.

How much does a gas line inspection cost in Bellevue?

$185–$350 for a standard residential inspection and pressure test. Add $95–$195 for CSST bonding verification and documentation if not included.

What happens if the inspection finds a problem?

If the pressure test fails, the plumber locates the leak with a combustible gas detector and provides a repair quote. The gas stays off until the repair is made and the system re-passes a pressure test.

A failed pressure test does not mean the system is immediately dangerous — a small leak at a fitting is different from a ruptured line. But the gas service stays off until the leak is repaired and the system passes a re-test. Puget Sound Energy (PSE) will not re-light appliance pilots on a system with a known failed pressure test.

Common findings: corroded fittings on aging black iron piping, missing sediment traps on appliances that require them (gas furnaces, water heaters), CSST without arc-fault bonding, and shutoff valves that no longer close fully. All of these are repairable; the cost depends on the extent.