Quick answer: The most common signs of a gas leak include the smell of rotten eggs (mercaptan odorant added to natural gas), a hissing sound near gas lines or appliances, dead vegetation above underground gas lines, higher-than-expected gas bills, and physical symptoms like dizziness or headaches near gas appliances. If you suspect a gas leak, leave the house immediately and call SDG&E at (800) 611-7343.
5 Warning Signs of a Gas Leak
1. The Smell of Rotten Eggs
Natural gas is odorless in its raw state. SDG&E (San Diego Gas & Electric) adds a chemical called mercaptan that produces a strong rotten egg or sulfur smell specifically so leaks can be detected. If you smell this odor anywhere in your home — especially near the water heating system, furnace, stove, or gas meter — treat it as a gas leak until proven otherwise.
2. A Hissing or Whistling Sound
Gas escaping from a cracked pipe, loose fitting, or damaged valve produces an audible hissing sound. This is most commonly heard near gas appliance connections, at the gas meter, or along exposed gas lines in the garage or basement. A hissing sound near a gas line is never normal and always warrants investigation.
3. Dead or Dying Vegetation
Underground gas lines that develop leaks release gas into the surrounding soil. The gas displaces oxygen that plant roots need, killing vegetation in a localized area directly above the leak. If you notice a strip of dead grass or dying plants in an otherwise healthy yard, an underground gas line leak is one possible cause.
4. Unusually High Gas Bills
A gradual increase in your gas bill without a corresponding increase in usage can indicate a leak somewhere in the gas distribution system between the meter and your appliances. Even small leaks waste measurable amounts of gas over a billing cycle.
5. Physical Symptoms
Prolonged exposure to even low concentrations of natural gas can cause headaches, dizziness, nausea, fatigue, and difficulty breathing. If multiple family members experience these symptoms simultaneously — especially when the symptoms improve after leaving the house — a gas leak should be investigated immediately.
What to Do If You Suspect a Gas Leak
- Do not turn on or off any light switches, electrical appliances, or anything that could create a spark
- Do not use your cell phone inside the house
- Do not light matches, candles, or cigarettes
- Open doors and windows as you exit to ventilate the space
- Leave the house immediately — take your family and pets
- Call SDG&E at (800) 611-7343 from outside the home or from a neighbor's phone
- Call a licensed plumber with gas line repair experience for follow-up repair once SDG&E has cleared the immediate danger
Common Causes of Gas Line Problems
- Corroded fittings: Gas pipe connections, especially older threaded galvanized steel fittings, corrode over time and develop slow leaks at the threads
- Aging flexible connectors: The flexible gas connectors that attach appliances to the gas supply have a limited lifespan and can crack or deteriorate, especially older brass connectors manufactured before 2000
- Appliance installation errors: Improperly connected gas appliances — often from DIY installations or unqualified handymen — are one of the most common causes of residential gas leaks
- Earthquake damage: Seismic activity can shift gas line connections, crack rigid pipe, and loosen fittings throughout the distribution system
- Construction and landscaping: Digging, trenching, or driving stakes near underground gas lines can puncture or damage the pipe
When Professional Gas Line Repair Is Needed
Even without a leak, there are situations where professional gas line work is necessary:
- New gas appliance installation: Adding a gas stove, outdoor grill, fire pit, pool heater, or tankless hot water system requires extending gas lines and ensuring adequate supply pressure
- Upgrading from a tank to tankless hot water unit: Tankless units often require a larger-diameter gas line (3/4-inch or 1-inch) than the existing half-inch line that served the tank unit
- Gas line relocation: Kitchen remodels, bathroom additions, or outdoor living projects may require rerouting existing gas lines
- Old system inspection: If your home has original gas piping from the 1960s or 1970s, a professional pressure test and visual inspection can identify deteriorating connections before they develop leaks
Why Gas Line Work Is Never a DIY Project
California law requires gas line work to be performed by licensed plumbing or HVAC contractors. There are no exceptions for homeowner self-work on gas systems, and for good reason:
- Safety: An improperly sealed gas connection can fill a home with explosive natural gas. The consequences range from serious injury to loss of life
- Code compliance: Gas installations must meet California Mechanical Code and California Plumbing Solutions Code requirements for pipe sizing, material, support, and ventilation
- Insurance: Gas work performed without proper licensing and permits may void your homeowner's insurance coverage for fire or explosion damage
- Pressure testing: Every gas line modification requires a pressure test to verify there are no leaks before the system is charged with gas
Need Gas Line Service?
Our licensed plumbers handle all gas line repairs, installations, and leak detection. Fully licensed, insured, and code-compliant. Emergency service available 24/7.
Call (619) 853-8491Frequently Asked Questions
Gas line repair costs vary based on the scope. A simple fitting repair or connector replacement typically costs $150 to $400. Running a new gas line to an appliance costs $300 to $800. Larger projects like extending gas service to an outdoor kitchen or upgrading a gas line for a tankless water heater run $500 to $1,500. All gas work includes pressure testing.
SDG&E inspects the gas lines from the street to your meter. Everything from the meter into your home is the homeowner's responsibility. We recommend a professional inspection every 5 to 10 years, or immediately if you notice any warning signs. Homes over 30 years old should have an inspection as a baseline.
No. California requires all gas line work to be performed by a licensed contractor. This includes connecting gas appliances, even if a gas stub-out already exists at the location. Improper connections are a leading cause of residential gas leaks.
Modern residential gas installations in California typically use CSST (corrugated stainless steel tubing) for interior distribution and black steel pipe for larger-diameter runs. CSST is flexible, faster to install, and requires fewer fittings than traditional black iron pipe, reducing potential leak points.
The mercaptan odorant added to natural gas produces a distinctive sulfur or rotten egg smell at detectable concentrations. However, in very small leaks, at outdoor locations with wind, or in areas where the odorant has been absorbed by soil, the smell may be faint or absent. This is why physical symptoms, dead vegetation, and gas bill increases are important secondary indicators.
The Bottom Line
Gas line safety isn't something to gamble with. A small leak can fill a confined space with explosive gas in minutes, and the consequences of ignition are catastrophic. The warning signs — the smell, the hissing sound, the dead plants, the unexplained bill increase — are nature's way of telling you something needs attention.
If you smell gas, get out and call SDG&E. If you need gas line repair, extension, or a professional inspection, call a licensed plumbing professional who specializes in gas work. It's one of those areas where cutting corners or doing it yourself simply isn't worth the risk.
