Common Causes of Gas Leaks

Excavation Damage

Excavation damage is the leading cause of gas distribution incidents in the United States, according to PHMSA data on our site. It happens when someone digs — for construction, landscaping, fence posts, or utilities — and hits a buried gas line.

Every state has a "Call Before You Dig" program (usually 811) that marks underground utility lines for free before excavation. Despite this, strikes still happen when contractors skip the call, markings fade, or lines aren't where records say they are.

Aging Infrastructure

Much of the U.S. gas distribution system was built in the mid-20th century. Some cities still rely on:

• Cast iron pipes — brittle, prone to cracking, especially with ground movement or temperature changes. Many were installed before the 1960s.
• Bare steel pipes — corrode without protective coating. Being phased out but still in service in many areas.
• Vintage service connections — the pipe running from the street main to your building may be decades old and deteriorating.

Utilities are gradually replacing these materials with modern polyethylene (PE) pipe, but the replacement programs span decades. In the meantime, aging pipes remain a significant source of leaks.

Corrosion

Metal gas pipes corrode over time, particularly:

• External corrosion — soil chemistry, moisture, and stray electrical currents eat away at the pipe's exterior. Especially common in wet climates or areas with acidic soil.
• Internal corrosion — less common in gas lines than water lines, but it does occur, particularly in older bare steel pipes.

Modern systems use cathodic protection (a small electrical current that slows corrosion) and protective coatings, but older pipes may lack both. You can filter incidents by corrosion on our site to see how prevalent it is in your state.

Natural Forces

Environmental events can damage gas infrastructure:

• Earthquakes can shift or rupture underground pipes, especially rigid cast iron lines that can't flex.
• Frost heave — repeated freeze-thaw cycles cause the ground to expand and contract, stressing pipe joints.
• Flooding — erosion can expose and damage buried pipes, and saturated soil increases corrosion.
• Ground subsidence — shifting soil from drought, mining, or groundwater withdrawal can crack or pull apart pipe joints.

Areas with seismic activity or extreme weather see more natural force incidents. View natural force incidents on our site.

Equipment Failure

Gas meters, regulators, valves, and service connections can fail due to:

• Manufacturing defects
• Wear over time (especially moving parts like regulator diaphragms)
• Improper installation
• Lack of maintenance

Equipment failures tend to cause smaller leaks that are caught during routine utility inspections, but they can escalate if undetected.

Incorrect Operation

Human error causes a meaningful share of incidents:

• Improper appliance installation or connection
• Maintenance errors by utility workers or contractors
• Unauthorized modifications to gas piping
• Failure to follow operating procedures during line work

These incidents are often preventable with proper training and adherence to safety protocols. Explore all incident causes and trends on our site.