Working with Natural Gas Lines: Safety Protocols Every Plumber Must Follow

Natural gas has no tolerance for shortcuts. A single improperly tested joint can cause a fire or explosion. This guide covers the safety procedures that licensed plumbers follow on every gas job.

Before You Start: Know the System

1. Identify the gas type. Natural gas (methane) and propane (LP) have different specific gravities, pressure requirements, and pipe sizing tables. Natural gas is lighter than air and rises; propane is heavier and settles in low areas. This affects where you look for leaks and how you ventilate.
2. Locate the main shutoff. Know where the gas meter and main shutoff valve are before opening any joints. In a multi-unit building, know whether shutting off one meter shuts off adjacent units.
3. Check for existing leaks. Before opening any joints, test the system at the meter with a manometer or gas detector. If the pressure is dropping at static test, there is already a leak somewhere. Find it first.

Pressure Testing (IFGC Chapter 4)

IFGC Section 406.4 requires a pressure test before covering or concealing any gas piping. Standard test for low-pressure systems (residential):

• Test medium: Air or nitrogen (never oxygen; never the gas itself for a new system test)
• Test pressure: 1.5 times the operating pressure or 3 psi, whichever is greater (typically 3 psi for residential)
• Test duration: Minimum 15 minutes, no pressure drop

For medium-pressure systems (above 2 psi), the test pressure is 1.5 times operating pressure. Your AHJ may require longer duration or witnessed tests.

Pressure gauge selection: Use a gauge calibrated for the test range. A 0-30 psi gauge for a 3 psi test gives good resolution. A 0-300 psi gauge at 3 psi tells you almost nothing useful.

Leak Detection

Soap solution: A commercially available gas-leak detector solution (or dish soap diluted in water) applied to every joint will bubble at any leak. Cover 100% of joints on every test -- not just the ones you made. Old joints can fail under test pressure.

Electronic gas detector: For residential service calls, an electronic detector sniffs for gas concentrations and alerts before you smell anything. Use it to locate the general area of a leak before going joint by joint with soap.

What NOT to use: Never use an open flame to check for gas leaks. This is how fires and explosions start.

Purging Procedures

Before lighting any appliance on a new or repaired system:

1. Close all appliance valves.
2. Open the main shutoff slowly.
3. Purge at the farthest appliance: open the appliance valve and let gas flow until you can smell gas (natural gas with odorant) or detect it electronically. For propane, give the line at least 30 seconds of flow at each appliance to purge air.
4. Wait 5 minutes after purging before attempting ignition to allow any released gas to dissipate.

When to Call the Utility

Some work requires the gas utility to participate:

• Meter disconnects and reconnects: The utility owns everything up to and including the meter. Do not disconnect or reconnect at the meter yourself.
• Service line work: Any work on the service line from the street to the meter is utility-owned. Call 811 before any excavation.
• New service: A new gas service requires a utility permit and inspection in addition to your mechanical permit.

Key Standard

IFGC (International Fuel Gas Code) Chapter 4 covers installation and testing of fuel gas piping. Always verify with your local adopted code version -- many jurisdictions amend IFGC requirements.