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First decide: evacuate or investigate
Before any testing, judge the severity. A strong, obvious rotten-egg smell, a hissing sound near a gas line, or any dizziness and headache means stop, leave the building with everyone, and call your gas utility and 911 from outside. You do not test a serious leak yourself; you get out and let the professionals clear it. Testing is only for a faint, intermittent, or suspected leak where the air is clearly safe to be in.
If you are confident the situation is minor, a hint of smell you want to confirm, a connection you reworked, you can run a controlled test. Ventilate the area, do not light anything, do not run electrical switches in the immediate space, and keep ignition sources away. If at any point the smell intensifies, abandon the test and evacuate. Our gas smell in the house page lays out the evacuate-first decision in detail.
The soap-bubble test on connections
The soap-bubble test is the safe, reliable home method, and it is what plumbers use to pinpoint a leak at a fitting. Mix a little dish soap with water into a thick solution (or use a dedicated leak-detection spray), then brush or spray it onto every threaded connection, valve, and joint along the suspect line: the appliance connector, the shutoff valve, the union fittings, the meter connections.
Watch the wetted joints for 30 seconds. Escaping gas pushes through the soap film and grows a steady cluster of bubbles right at the leak point, so the bubbles literally mark the spot. A connection that stays still is sound. This works because it needs no power, no flame, and no special tool, and it isolates exactly which fitting is leaking rather than just telling you gas is present somewhere. Tighten or repair what bubbles, then re-test.
- ·Mix dish soap and water into a thick solution, or use leak-detection spray
- ·Brush it onto every threaded joint, valve, and union on the line
- ·Steady, growing bubbles mark the exact leak point
- ·No power, no flame, no special tool required
Electronic detectors and the meter test
A handheld electronic gas detector (a combustible-gas sniffer, $30 – $100) is the next tool up. You sweep the probe slowly along lines, fittings, and appliance bases, and it beeps or reads out when it senses gas in the air. Detectors are great for finding which area is leaking when the soap test has not isolated it, though they tell you gas is present rather than pinpointing the exact fitting the way bubbles do. Use the two together: the detector narrows the zone, soap confirms the joint.
The meter test checks the whole system for a slow leak. Turn off every gas appliance and pilot in the house, then watch the gas meter dial (the smallest, fastest-moving dial). With nothing drawing gas, it should sit perfectly still. If it creeps, gas is escaping somewhere in the system even with all appliances off, which confirms a leak worth tracking down. This is a good first screen when you suspect a leak but cannot smell its location.
Never a flame, and when to call it in
The one rule that overrides everything: never use a match, lighter, or any open flame to test for a gas leak. It sounds obvious, but people still try to listen for a flame change or hold a lighter near a fitting. A gas-air mixture only needs one spark, and the test itself becomes the ignition source. Soap bubbles and detectors exist precisely so you never have to bring fire near a suspected leak.
Some leaks are beyond a homeowner test: leaks at the meter or before it, leaks inside a wall or under the slab, a smell you cannot locate, or any leak you confirm but cannot stop. Those belong to a licensed plumber or the utility, who will run a formal pressure test on the system. The gas leak repair cost page covers what pressure testing and the repair itself run, and for confirming a leak by smell before you ever test, see what a gas leak smells like.
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