7 Warning Signs of a Gas Leak Every Homeowner Must Know

Natural gas is odorless and invisible. The only reason you can detect a leak at all is that utilities add mercaptan — the rotten-egg smell — as a warning. But not every leak announces itself with a strong odor. Here are the seven warning signs of a gas leak every San Bruno homeowner should know, and exactly what to do about each one.

1. The rotten-egg smell

This is the big one. If you smell sulfur or rotten eggs near an appliance, the meter, or anywhere in the house — act immediately. Leave the house. Don’t flip switches, don’t light anything, don’t use your phone indoors. Call 911 and your gas utility from outside. Once cleared, call us at (833) 713-2101 for detection and repair.

2. Hissing or whistling near gas lines

A distinct hissing sound near piping, the meter, or an appliance connection means gas escaping under pressure. Even a faint hiss deserves immediate attention — small leaks at high pressure can release significant gas over hours.

3. Dead or dying vegetation in one spot

Leaking underground gas displaces oxygen in the soil, killing grass and plants above the leak while everything around them stays green. In Belle Air, where the water table runs high, we trace many leaks by exactly this sign — a brown patch in an otherwise healthy lawn marking the break below.

4. Pilot lights and burners misbehaving

Pilots that won’t stay lit, burners with weak yellow flickering flames instead of steady blue, or appliances that worked fine for years and suddenly don’t — these can signal pressure loss from a leak upstream. If multiple appliances act up at once, suspect the line, not the appliances.

5. Physical symptoms that ease outdoors

Headaches, dizziness, nausea, or fatigue that improve when you leave the house and return when you’re home — take this seriously. Get everyone out, get fresh air, and call emergency services. Carbon monoxide from incomplete combustion is the parallel danger here; make sure your CO detectors are working.

6. A gas bill that climbs for no reason

No new appliances, no change in habits, but the bill keeps rising? A slow leak bleeds gas — and money — 24 hours a day. Compare usage (therms), not just dollars, to rule out rate changes.

7. Visible damage to exposed piping

Corrosion, rust flaking, damaged coatings on the meter riser, or pipe that’s been hit, bent, or buried by landscaping work. Crestmoor hillside homes see this at the house entry point, where soil movement stresses the lateral-to-riser transition.

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What to do (and not do)

Do: leave immediately, call 911 and the utility from outside, keep everyone (and pets) out until cleared.

Don’t: flip light switches, use phones or flashlights indoors, light matches or candles, start cars in an attached garage, or try to find the leak yourself.

After the emergency: getting your gas back

Once the utility clears the property or red-tags the meter, the path back to normal runs through professional work: electronic leak detection to pinpoint the source, code-compliant repair, a full pressure test to prove system integrity, and coordinated re-inspection. We handle that entire sequence with one call.

San Bruno learned about gas safety the hard way in 2010. Don’t gamble with warning signs — if any of these seven show up, call (833) 713-2101 now. Our emergency line is answered 24/7.