6 Signs of a Gas Leak You Should Never Ignore

A close call in Mosman that still gives me chills

I got called as a gas plumber to a house in Mosman where the owners had been smelling gas for three days. They thought it was "just the pilot light" on the hot water system. When I got there and sprayed gas detection spray on the copper gas line running through the subfloor, it went off like a fire extinguisher. A tiny pinhole leak from copper gas line corrosion — could have been nasty if it had ignited. The owner said, "I thought the smell was normal for an old house." I told him flat out: no smell of gas is normal. Ever.

In Neutral Bay and Mosman, old infrastructure means old pipes. Here's what I look for.

Six signs I tell my customers to watch for

• Rotten egg smell — the most obvious one. Gas companies add mercaptan so you can smell it. If it smells like sulphur or a dead animal, treat it seriously.
• Hissing or whistling near gas lines — a pressurised leak makes noise. If you hear a hiss that's not a tap or sprinkler, don't go looking for it. Get out and call.
• Dead vegetation above gas pipes — gas leaking underground starves plant roots of oxygen. A circular patch of dead lawn in a straight line above your gas line? That's a leak.
• Higher gas bill with no change in usage — compare to the same period last year. If it's 20-50% higher and you haven't changed your habits, call me to pressure-test the system.
• Headaches, dizziness, nausea — if multiple people in the house feel unwell indoors and better outside, you may have a gas leak. Get out and call.
• Bubbles in puddles above gas lines — gas escaping through wet soil creates bubbles. Most visible after rain.

When to call me

If you notice any of these signs, call a licensed gas plumber. Even a slow leak wastes money and is a safety risk. If the smell is strong or you hear a clear hiss, evacuate first, call 1800 GAS LEAK from outside, then call me to repair the leak after the supply's been isolated.

I use electronic gas detectors, pressure testing, and bubble tests to find leaks fast. Most gas leak repairs on the Northern Beaches take under two hours and cost $200–500. As an emergency plumber, I serve every suburb from Mosman to Avalon.

Why older suburbs like Mosman and Neutral Bay see more gas leaks

Older homes with old infrastructure are the biggest source of gas leak callouts I attend. In Mosman and Neutral Bay, many properties from the 1950s–70s still have original copper gas pipes under suspended timber floors. These pipes are exposed to moisture from poor subfloor ventilation and corrode from the inside out. A pipe that looks fine externally can have paper-thin spots internally.

For coastal suburbs like Dee Why and Brookvale, salt spray accelerates corrosion on external gas fittings. And any property with a gas continuous-flow hot water system should check the gas connection fitting annually — the vibration can slowly loosen it at the isolation valve.

Related reading

• What to Do If You Smell Gas at Home— If you have confirmed a leak, here is exactly what to do.
• What Counts as a Plumbing Emergency?— Gas leaks are always classified as emergencies.