Is it safe to store gasoline in an attached garage with a gas water heater?

Short answer

Why people ask this

People worry specifically about the pilot flame or burner on a gas water heater igniting gasoline vapors in an attached garage. They also know fumes can drift into the house through the shared wall or door. An attached garage narrows escape paths for vapors, and gas appliances introduce ignition sources near the floor. Homeowners want to balance convenience with code requirements and insurance rules.

When it might be safe

• You keep 1–2 gallons max in a certified (UL/FM or CARB) gasoline container or metal safety can with a tight, spring-closing cap.
• The containers are stored at least 5–10 feet from the gas water heater and any ignition source, and not down-slope of the heater if the floor is pitched.
• The water heater is a sealed-combustion/direct-vent model (no open pilot in the garage air), and the garage has no floor drains or sumps where vapors could collect.
• Containers sit in a small, non-sparking spill tray or flammable-storage cabinet, out of sun and away from the door into the house.
• Local code allows it, and you limit storage duration (fresh fuel, rotated, stabilized if needed) with a CO/smoke alarm near the garage-to-house door.

When it is not safe

• Storing gas within a few feet of a gas water heater with an open pilot or burner intake at floor level.
• Using improvised or vented containers (e.g., milk jugs) that can leak fumes toward the heater.
• Keeping more than a small quantity (e.g., multiple 5-gallon cans) in an attached garage.
• Placing containers where heavier-than-air fumes can travel toward the heater—low spots, near floor cracks, or toward the burner access.
• Locating cans next to battery chargers, power tools, or extension cords that can spark, especially near the water heater.
• Ignoring local fire code, HOA, or insurance limits for attached garages with fuel-fired appliances.

Possible risks

• Ignition of gasoline vapors by the water heater’s pilot/burner leading to a flash fire or explosion.
• Vapor migration into the home through the door or utility penetrations in the shared wall of the attached garage.
• Health exposure from chronic fumes (benzene and other VOCs) accumulating in an enclosed attached space.
• Container degradation or heat expansion causing leaks, especially near appliances or sun-warmed walls.
• Insurance denial or code violations if fuel is stored improperly near a gas appliance.

Safer alternatives

• Store gasoline in a detached shed or outdoor-rated, lockable flammable-storage cabinet away from any gas appliance.
• Keep only what you’ll use immediately and buy fresh fuel as needed instead of long-term storage in an attached garage.
• Switch to battery-electric yard tools to reduce or eliminate gasoline storage at home.
• If you must store some fuel, use a metal safety can and place it in a ventilated, detached location with secondary containment.
• Consider a sealed-combustion/direct-vent water heater upgrade if you routinely need limited fuel on-site.

Bottom line

In an attached garage with a gas water heater, gasoline storage is only conditionally acceptable: keep very small amounts in approved, tightly sealed containers, placed well away from the heater’s ignition sources, and within local code limits. If you can’t meet those conditions—or need to store more—use a detached, outdoor-rated location instead.

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