The 5 Silent Signs of a Gas Leak in Your Home, and What to Do First

What to do in the first 2 minutes

A suspected gas leak is not something to investigate first and act on later. Natural gas needs only a small concentration in air and a single spark, and that spark can come from a light switch, a fridge thermostat or a phone screen waking up.

1. Get everyone out, pets included, and leave the door open behind you.
2. Touch nothing electrical. No switches, no power points, no exhaust fans, no phones, no garage remote.
3. Open a door or window you pass, if it costs no time. Do not walk the house opening up while the smell builds.
4. Turn the gas off at the meter only if it is outside and safe to reach. A quarter turn, handle across the pipe, shuts the supply.
5. Call 1800 427 532 (1800 GAS LEAK) from outside. That is the free 24 hour emergency line for the South Australian gas network.
6. Call 000 instead if there is fire, if anyone is drowsy, confused or nauseous, or if the escape is from a street main.
7. Stay outside until someone qualified says the building is safe. Nobody goes back for a phone charger.

On bottled LPG, which most Adelaide Hills properties beyond the reticulated network run on, 2 things change. Shut the valve at the cylinder rather than a meter, and ring the emergency number printed on the cylinder label. LPG is heavier than air, so it pools in cellars, pits and sunken laundries instead of dispersing.

The 5 signs, and what each one is telling you

These run from most urgent to least. Only the first 2 mean leave the house now. The other 3 mean book a licensed gas fitter rather than wait.

A rotten egg or sulphur odour. Natural gas comes out of the ground with no smell at all. What you smell is mercaptan, dosed in on purpose at a concentration detectable well below the level at which gas becomes flammable. That margin is the design intent, so trust the odour.

A hiss, a whistle or a rush of air near a fitting. Sound means the escape is large enough to move volume, and it is the sign least likely to be imagined. Listen at the meter, at appliance isolation valves, at the hose behind a freestanding cooker, and at the point capped off when an old wall furnace was removed.

Dead grass or dying plants in a line. Gas escaping from a buried service line displaces oxygen in the soil and kills the root zone above it. The tell is the shape: a narrow strip tracking from meter to house while the lawn either side stays green. It shows up in a wet winter as readily as a dry summer, which separates it from drought stress.

Yellow, lazy or sooting flames. A correctly burning natural gas flame is crisp and blue with a small yellow tip at most. Floppy orange flames, soot above a heater, a pilot that will not stay lit and a burner that lights with a delayed thump all point to incomplete combustion, which is how carbon monoxide gets made.

A gas bill that rose with nothing else changing. Compare the daily average rather than the total, because billing periods differ in length. A steady climb across 2 or 3 bills, same appliances and comparable weather, points to gas going somewhere downstream of the meter that nobody is using.

Carbon monoxide, the sign you cannot smell

Carbon monoxide has no smell, no colour and no taste. It is not what leaks out of a pipe, it is what comes out of an appliance burning gas badly, and it kills people in their homes every winter in Australia. Nothing protects you from it except a working alarm and a serviced appliance.

The symptom pattern is the giveaway, because it mimics winter flu: headache, nausea, dizziness, heavy tiredness. The difference is that symptoms improve when you leave the house and return when you come back, and they hit everyone in the building at once, pets included. A whole family with the same flu that clears at work and at school is a carbon monoxide investigation, not a virus.

• Highest risk: open-flued space heaters and open-flued ducted heating, which take combustion air from the room and vent on a weak natural draught.
• Next: unflued portable heaters run in a closed room, and any gas appliance where a rangehood, exhaust fan or ducted vacuum can pull exhaust back down the flue.
• Any appliance with soot marks, a yellow flame, a pilot that will not hold, or a flue terminal blocked by a nest or leaf litter.

Where leaks actually turn up in Adelaide homes

Reticulated natural gas across metropolitan Adelaide is distributed by Australian Gas Networks, which owns the street main, the service line into the property and the meter. Everything from the meter outlet onwards belongs to the owner, and that is where the great majority of domestic leaks sit.

• Threaded joints in old black steel pipe. Inner-south stock in Goodwood, Unley, Norwood and Colonel Light Gardens was commonly piped in steel from the 1950s. The barrel survives, the cut threads corrode first, and a damp sub-floor under a suspended villa is ideal for it.
• Capped and abandoned points. Every wall furnace pulled out and every cooker relocated left a point behind. Most were capped properly. Some were plugged with a fitting never meant to be permanent, then tiled over.
• Flexible appliance connections. The hose behind a freestanding cooker gets kinked and dragged every time the oven is pulled out, and it has a finite service life.
• Damaged meter risers. Meter boxes on a narrow allotment sit exactly where a reversing car or a garden edge dug too close will find them.
• Ground movement. Adelaide reactive clay swells through winter and shrinks hard through summer, flexing a rigid steel service line twice a year, every year.
• Renovation damage. The highest-risk moment for a gas leak in an Adelaide home is a renovation, when somebody drills, core-cuts or trenches without knowing what runs behind the wall.

Past the reticulated network the Hills run on bottled LPG, and the failure points move. It is rarely the buried line and almost always the regulator, the pigtail hose or the changeover valve. Those sit outdoors in full sun, and ultraviolet light degrades rubber long before the metalwork gives up.

When it is not a gas leak

Plenty of gas callouts turn out to be something else, and saying so is more useful than treating every rotten egg smell as an emergency. These 3 account for most of them.

• A dry trap. Sewer gas smells of rotten eggs too, because it carries hydrogen sulphide. If the smell sits at floor level in a bathroom or laundry, worst near a shower or floor waste unused for weeks, the water seal has evaporated. Tip a bucket of water down it.
• Dust burning off a heater. The first run in autumn gives a scorched smell for 10 to 20 minutes as months of dust burns off the heat exchanger. It does not smell of rotten eggs and it fades.
• The ignition whiff. A brief smell at the instant a burner lights, clearing immediately, is unburnt gas from the ignition sequence. On an old appliance that is normal. Every time, or with a delayed ignition that thumps, is a service issue.

The honest position: if you are not sure, get out and call. A false alarm is the worst outcome, and it is a small one set against the alternative.

Who is responsible, and what a gas fitter does

The work runs in order. The gas fitter connects a manometer at a test point and runs a soundness test in line with AS/NZS 5601.1: the line is pressurised and watched, and any drop proves gas is going somewhere. That settles whether there is a leak before anyone guesses where. Localisation follows with an electronic detector and leak detection solution along joints and appliance connections, then the repair, then the test again.

An appliance that fails on carbon monoxide, flue integrity or clearances gets disconnected and tagged rather than left in service with a warning. That is the outcome the standard requires.

What the job should leave you with on paper:

• The pressure test result in writing, with the figures on it.
• A plain description of what was repaired or replaced.
• A note of any appliance tagged out of service, and why.
• A Certificate of Compliance for the gas work, required in South Australia and what an insurer or a conveyancer asks for.

Marc is a licensed plumber and gas fitter with 20 years behind him, and he attends the jobs himself. You get a text with an arrival time before he sets off, and the price is discussed up front. The honest answer on a gas call is often that the installation is sound and the smell is from somewhere else.

Questions we get asked

References

• Government of South Australia, Office of the Technical Regulator: gas safety and licensing
• Standards Australia, AS/NZS 5601.1 Gas installations
• ACCC Product Safety Australia: gas appliance and carbon monoxide safety