Natural gas is the energy backbone of most Los Altos properties. It heats water, powers stoves and ranges, and fuels furnaces — operating quietly and invisibly behind walls and under floors without incident the vast majority of the time. But natural gas is a flammable, pressurized fuel delivered through a system of pipes, fittings, and appliance connections that age, corrode, and fail. When they do, the result can be a leak that goes undetected for hours or longer.
The U.S. Fire Administration identifies natural gas leaks as a leading cause of residential fires and explosions in the United States. The danger is compounded by the fact that natural gas in its raw form is colorless and odorless. Utility companies add a chemical odorant called mercaptan to make leaks detectable by smell — but that odorant can fade, can be masked by other household odors, and is not detectable by everyone. Relying on smell alone is not a complete detection strategy.
Here are the five warning signs every Los Altos property owner needs to know.
Warning Sign #1: The Smell of Rotten Eggs or Sulfur
The most widely recognized indicator of a natural gas leak is the distinctive sulfur-like odor that mercaptan imparts to distribution gas — most people describe it as rotten eggs or a skunk’s spray. The California Public Utilities Commission requires that all natural gas distributed to California customers be odorized to levels detectable well below the flammable range. That requirement exists precisely because it provides the most accessible early warning available.
If you detect this odor anywhere in your Los Altos home or commercial property — near the kitchen, near a water heater or furnace, near a gas meter, or anywhere along a gas line — treat it as a potential gas leak immediately. The strength of the smell matters, but should not be the deciding factor in your response. A faint rotten egg odor can indicate a small leak that is actively growing. Neither a faint nor a strong odor warrants anything other than immediate evacuation and a call to emergency services.
Pro Tip: Never assume a sulfur smell has another explanation — a dead animal in the wall, a drain issue, or something on the stove. If you can’t immediately confirm the source, evacuate and call PG&E’s 24/7 emergency line at 1-800-743-5000. It’s always the right call.
Warning Sign #2: A Hissing, Whistling, or Blowing Sound
Gas under pressure produces an audible escape sound when it leaks through a crack, corroded pipe wall, loose fitting, or damaged connection. This sound is most commonly described as hissing — similar to air escaping a tire — but can also present as a steady whistle or, in the case of a significant high-pressure gas leak, an audible blowing. It is typically continuous rather than intermittent and persists even when the associated appliance is turned off, because the supply line upstream is still pressurized.
The most common locations to hear this in a Los Altos home are near the gas meter, along supply lines in utility rooms or crawlspaces, near appliance shutoff valves, and at flexible gas connectors — the corrugated metal hoses that connect supply lines to ranges, dryers, and water heaters. These flexible connectors are among the most common points of failure in residential gas systems, particularly in older homes.
If you hear any unexplained hissing or blowing near a gas appliance, gas line, or meter, stop what you’re doing and evacuate. Do not attempt to locate the source by getting closer.
Pro Tip: Drain and Water’s gas line services include inspection and replacement of aging gas line infrastructure — including flexible connectors — throughout the Los Altos service area. Appliances more than fifteen years old are worth a professional look even in the absence of active symptoms.
Warning Sign #3: Dead or Dying Vegetation Above a Gas Line
This warning sign is specific to underground gas line leaks. Buried supply lines that develop gas leaks often can’t be detected by smell or sound because escaping gas disperses into the soil before reaching the surface. The visual evidence of a buried leak is frequently the first accessible indicator.
Natural gas displaces oxygen in soil, starving plant roots of what they need to function. The result is localized vegetation death, wilting, or discoloration that follows the path of the buried gas line without any other obvious cause. In wet conditions you may also observe persistent bubbling in standing water or puddles along the gas line path. The California State Fire Marshal treats underground gas line leaks as priority emergencies because escaping gas can accumulate in basements and crawlspaces even when the gas leak originates outside the building.
If you observe unexplained dead patches or bubbling water in the vicinity of your buried gas line, call PG&E’s emergency line immediately and do not re-enter the building until it has been assessed and cleared.
Warning Sign #4: Physical Symptoms in Occupants or Pets
Natural gas displaces oxygen in enclosed spaces, and the physical symptoms of exposure are directly attributable to that displacement: persistent headache, dizziness, nausea, unexplained fatigue, difficulty concentrating, and in prolonged exposure, shortness of breath or loss of consciousness. The diagnostic pattern to watch for is location-dependence — occupants who feel unwell inside and improve when they go outside, with symptoms returning upon re-entry.
Pets often show symptoms before human occupants do, since they occupy lower elevations where gas settles and spend more time in specific areas of the building. Unusual lethargy, disorientation, or loss of appetite in pets — particularly when paired with any of the other warning signs — warrants immediate attention.
The California Department of Public Health recommends that households with gas appliances install both natural gas detectors and carbon monoxide detectors on each floor, including near sleeping areas. These devices provide continuous, objective monitoring that is not subject to human sensory limitations or odor fade.
Pro Tip: Persistent unexplained headaches or fatigue that your household has normalized over time — particularly in homes with enclosed gas appliances — can indicate a slow gas leak accumulating gradually. If this resonates, schedule a professional gas line assessment before the symptoms become an emergency.
Warning Sign #5: Appliance Irregularities — Flame Color, Pilot Outages, and Unexplained Bills
The fifth category of warning signs is functional: changes in how your gas appliances behave. A properly burning gas burner produces a steady blue flame. Yellow, orange, or red flames indicate incomplete combustion — meaning the air-to-gas ratio is off, or the burner is receiving more gas than it can efficiently burn. Persistent off-color flames on any gas appliance warrant professional inspection.
Frequent pilot light outages on older water heaters or furnaces can indicate fluctuating gas pressure or a supply line problem. And an unexplained increase in your PG&E gas bill — when occupancy, usage habits, and seasonal demands haven’t changed — can indicate that gas is escaping somewhere in the system before being consumed by an appliance.
The table below summarizes all five warning signs and the appropriate first response:
| Warning Sign | What It Indicates | First Response |
|---|---|---|
| Rotten egg / sulfur odor | Mercaptan odorant in escaped gas | Evacuate immediately; call PG&E and 911 |
| Hissing or blowing sound | Pressurized gas escaping a line or fitting | Evacuate immediately; do not investigate |
| Dead/dying vegetation or outdoor bubbling | Underground gas line leak | Call PG&E emergency; do not enter building |
| Physical symptoms — headache, nausea, dizziness | Oxygen displacement from accumulated gas | Evacuate; fresh air; call 911 if symptomatic |
| Abnormal flame color, pilot outages, high bills | Supply line or appliance irregularity | Schedule professional gas line inspection |
What to Do the Moment You Suspect a Gas Leak
Evacuate immediately — every person and pet exits the building now. Open doors and windows along your direct exit path as you leave, but do not go out of your way to ventilate other rooms. Do not operate any electrical devices — light switches, garage openers, appliance controls — because even a small spark can ignite accumulated gas. Do not start a vehicle in an attached garage. Once safely outside, call PG&E at 1-800-743-5000 and 911. Do not re-enter until emergency responders provide explicit clearance.
After the scene is cleared, a California Contractors State License Board-licensed plumber must inspect and repair the gas system before the utility restores service. This is not optional — PG&E will not reconnect gas until a licensed contractor has completed permitted repairs, passed a pressure test, and documented the work.
Need a licensed plumber for gas line repair in Los Altos after a gas leak event? Contact Drain and Water — available 24/7. CA License #1026232 | (408) 564-0580.
Proactive Gas Line Maintenance for Los Altos Properties
Los Altos has substantial housing stock dating to the 1950s–1970s, much of which has never had a comprehensive gas line inspection. Aging black iron supply lines, original flexible connectors, and decades of seismic activity — the Bay Area sits atop multiple active fault systems — create compounding risk in older gas systems. The California Governor’s Office of Emergency Services emphasizes post-earthquake gas line inspection as a critical safety practice for exactly this reason.
Drain and Water provides gas line inspection, repair, and replacement for Los Altos residential and commercial properties. Their licensed technicians assess supply lines, flexible connectors, shutoff valves, and appliance connections — identifying components approaching end of service life before they fail.
Pro Tip: If your home still has uncoated brass flexible connectors on any appliance, replace them now. The Consumer Product Safety Commission issued a safety advisory on these connectors due to stress corrosion cracking susceptibility. Current stainless steel corrugated connectors are a straightforward upgrade that eliminates one of the most common residential gas leak failure points.
Don’t wait for a symptom to become an emergency. Schedule a gas line inspection with Drain and Water — (408) 564-0580, available 24/7.
Frequently Asked Questions
Is natural gas naturally odorless? Yes — natural gas in its raw state is both colorless and odorless. The California Public Utilities Commission requires utility companies to add mercaptan, a chemical odorant that produces the familiar rotten egg smell, to all distributed gas. It’s added at concentrations detectable well below the flammable limit — but odor fade, olfactory desensitization, and individual variation in smell sensitivity mean it can’t be your only detection method. Installing a natural gas detector provides an objective, continuous safeguard.
Can a gas leak happen if I don’t smell anything? Yes. Odor fade can significantly reduce or eliminate detectable mercaptan, particularly in underground leaks where the gas travels through soil before surfacing. People with reduced olfactory sensitivity due to age, illness, or sinus conditions may not detect it even at concentrations obvious to others. The California Department of Public Health recommends natural gas detectors in all homes with gas appliances for precisely this reason — they provide detection that human senses alone cannot guarantee.
Does PG&E repair gas lines inside my home? PG&E is responsible for infrastructure up to and including the meter on your property. After responding to a leak, they will shut off service and assess the system to the meter — but internal gas lines, fittings, flexible connectors, and appliance connections are the responsibility of the homeowner and must be repaired by a licensed plumbing contractor. PG&E will red-tag your system until a licensed plumber completes repairs, passes a pressure test, and provides documentation. That post-incident repair work is exactly what Drain and Water handles for Los Altos property owners.
Are gas leaks more common in older Los Altos homes? Older homes carry meaningfully higher risk. Gas supply lines in pre-1990s construction may be black iron pipe subject to corrosion at fittings and threaded connections. Original uncoated brass flexible connectors — the subject of a Consumer Product Safety Commission safety advisory — may still be in place on older appliances. Decades of Bay Area seismic activity can also stress fittings and connections in ways not visible from the outside. If your home is more than 30 years old and has never had a gas line inspection, scheduling one is a sound proactive investment.
Does Drain and Water handle gas line service in Los Altos? Yes. Drain and Water is a licensed, family-owned San Jose plumbing company serving Los Altos and all of Santa Clara County. Their services include gas line inspection, repair, and replacement for residential and commercial properties, with 24/7 emergency availability. Reach them at (408) 564-0580 or at drainandwater.com. CA License #1026232.
Drain and Water Plumbing Services | San Jose, CA | CA License #1026232 | (408) 564-0580 | drainandwater.com
