6 Signs of a Gas Leak You Should Never Ignore
A gas leak can go unnoticed for weeks if you do not know what to look for. Here are six warning signs every Northern Beaches homeowner should know.
Six signs indicate a gas leak: the smell of rotten eggs (mercaptan), a hissing sound near gas lines, dead or dying vegetation above gas pipes, a sudden spike in your gas bill, physical symptoms like headaches and dizziness, and bubbles in water or damp soil near gas lines. Any one of these warrants a call to a licensed gas plumber. If you smell gas strongly or hear a clear hiss, evacuate first and call 1800 GAS LEAK from outside.
- • Rotten egg smell — the most obvious sign; evacuate and call 1800 GAS LEAK.
- • Hissing or whistling near gas meter or appliances — possible pressurised leak.
- • Dead vegetation in patches or lines above underground gas pipes.
- • Higher gas bill with no change in usage — hidden leak wasting gas.
- • Headache, dizziness, nausea — especially if multiple people are affected indoors.
- • Bubbles in puddles or wet soil above underground gas lines.
The 6 warning signs
These signs are listed roughly in order of urgency. The first two are immediate emergencies. The others may develop gradually but still need prompt attention.
Rotten egg smell (added mercaptan)
The most obvious sign. Gas companies add a chemical called mercaptan to natural gas so you can detect leaks by smell. It is deliberately unpleasant — like rotten eggs, sulphur, or a dead animal. If you notice this smell anywhere in your home, treat it seriously. The smell may be stronger near gas appliances, the gas meter, or along pipe runs in the roof cavity or under the house.
Hissing or whistling sound near gas lines
A pressurised gas leak makes a sound — usually a faint hiss or whistle near the gas meter, a gas appliance connection, or along a pipe run. If you hear a hissing sound that is not from a tap, fan, or outdoor sprinkler, investigate carefully. Do not search for the hiss if you can smell gas — evacuate instead.
Dead or dying vegetation near gas pipes
Natural gas leaks underground can starve plant roots of oxygen, causing patches of dead grass, shrubs, or garden beds directly above the pipe. If you have a circular patch of dead lawn or a hedge that is dying in a straight line, especially near where the gas line runs to your meter, this is a strong sign of an underground gas leak.
Higher than normal gas bill
A sudden spike in your gas bill without a corresponding increase in usage — same appliances, same habits — can indicate a leak somewhere in the system. Compare your current bill to the same period last year. If it is 20-50% higher and you have not changed your usage, call a gas plumber to pressure-test the system.
Physical symptoms (headache, dizziness, nausea)
Natural gas leaks displace oxygen in enclosed spaces, causing symptoms similar to carbon monoxide poisoning. If multiple people in your home experience headaches, dizziness, nausea, fatigue, or eye/throat irritation at the same time, especially if symptoms improve when you go outside, you may have a gas leak. Open windows and call a gas plumber.
Bubbles in water near gas lines
If you have an underground gas line and you see bubbles rising in puddles, damp soil, or wet grass directly above the pipe run, this can indicate gas escaping through the soil. This is most visible after rain when the ground is saturated, and the bubbles will continue even when the water is still.
When to call a plumber
Call a licensed gas plumber if you notice any of these signs. Even a small, slow gas leak wastes money and is a safety risk. If the smell is strong or you hear a clear hissing sound, evacuate first, call 1800 GAS LEAK from outside, and then call us to repair the leak after the supply has been isolated.
We use electronic gas detectors, pressure testing, and bubble solution to locate gas leaks with precision. Most gas leak repairs on the Northern Beaches take under two hours and cost $200-500 depending on the location and complexity. We serve all suburbs from Mosman to Avalon.
Northern Beaches considerations
The Northern Beaches has specific factors that make gas leaks more likely. In Dee Why and Brookvale, many homes from the 1970s and 80s still have original copper gas pipes. These develop internal pitting corrosion over time, especially in areas with reactive soils. A pipe that looks fine externally can have thin spots internally that eventually leak.
In Neutral Bay and Cremorne, many older homes have gas pipes running under suspended timber floors. These pipes are exposed to moisture from poor subfloor ventilation — a common issue on the lower north shore — and corrode faster than pipes in dry, well-ventilated spaces.
For any Northern Beaches property with a gas continuous-flow hot water system, check the gas connection fitting annually — these units vibrate during operation, which can slowly loosen the gas fitting at the isolation valve. A loose fitting is one of the most common minor gas leak causes we see.
Frequently asked questions
Can a gas leak be detected without a smell?
Yes — natural gas itself is odourless. The mercaptan smell is added for detection. If you cannot smell it (due to age-related smell loss, a cold, or COVID-19), you may not detect it by smell alone. This is why the other signs — hissing sounds, dying plants, physical symptoms, and higher bills — are important. Electronic gas detectors are also available and we recommend them for elderly residents.
How do gas plumbers find leaks?
Licensed gas fitters use electronic gas detectors (sniffers) that measure gas concentration in parts per million. They also use bubble solution on fittings and joints, and can pressure-test the entire gas system to confirm whether there is a leak and how significant it is. For underground gas lines, tracer gas methods can pinpoint the exact location.
What should I do if I suspect a gas leak but cannot smell anything?
Look for the other signs: dead vegetation, hissing sounds, higher bills, or physical symptoms. If any of these are present and you have a gas appliance or gas connection, call a gas plumber. They can pressure-test the system and confirm whether there is a leak. It is better to call and be told there is no leak than to miss a real one.
How common are gas leaks on the Northern Beaches?
Gas leaks on the Northern Beaches are most common in properties built between 1970 and 2000, where copper gas pipes have reached mid-life. Coastal corrosion in suburbs like Dee Why and Newport accelerates pipe degradation. We attend roughly 3-4 gas leak call-outs per week across the region, with the majority being minor leaks at fittings rather than full pipe failures.
Suspect a gas leak? Call a licensed gas plumber.
We pressure-test, locate, and repair gas leaks across the Northern Beaches. Same-day service available. Call now or book online.
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.