If you suspect a hidden gas leak inside your walls, treat it as an emergency first and an investigation second. Natural gas and LPG are both highly flammable and can be deadly, so your immediate priority is to get everyone out safely — then, once the situation is stabilised, you can work with a licensed gasfitter to locate and fix the problem.
Recognise the Warning Signs
Before you can find a hidden leak, you need to know what to look for. Common indicators include:
- The smell of gas — natural gas and LPG have a distinctive rotten-egg or sulphur odour added specifically so you can detect leaks. If you smell it near a wall, skirting board, or floor cavity, take it seriously.
- A hissing or whistling sound coming from inside a wall, even when no appliances are running.
- Dead or dying patches of grass or plants near exterior walls where underground pipes run — gas displaces oxygen in the soil.
- Unexpectedly high gas bills with no change in usage habits.
- Pilot lights that keep going out or appliances that won't stay lit.
- Dizziness, nausea, or headaches when indoors — these can be symptoms of gas exposure.
What to Do Immediately If You Suspect a Leak
This is the most important section. Follow these steps in order:
- Do not operate any electrical switches, appliances, or light switches — even a small spark can ignite gas.
- Do not use your mobile phone inside the building — step outside first.
- Extinguish all open flames — candles, cigarettes, gas hobs.
- Open windows and doors as you leave to ventilate the space.
- Turn off the gas at the meter or LPG cylinder if it is safe and quick to do so on your way out.
- Leave the building and keep others away.
- Call your gas retailer's emergency line or 111 from outside or a neighbour's property.
WorkSafe NZ provides clear guidance on gas safety emergencies and your obligations as a homeowner.
Safe Checks a Homeowner Can Do
Once the immediate danger has been assessed and cleared by emergency services or your gas retailer, there are a few non-invasive checks you can carry out yourself — but only if you are confident there is no active emergency.
The Soap-Bubble Test (Accessible Fittings Only)
Apply a solution of dishwashing liquid and water to any visible, accessible gas fittings, valves, or pipe joints (e.g., at the meter, behind an appliance). Bubbles forming indicate escaping gas. This only works on exposed connections — it cannot detect leaks hidden inside wall cavities.
Check Your Gas Meter
Turn off all gas appliances and pilot lights, then watch your gas meter for 10–15 minutes. If the dial or digital display is still moving, gas is flowing somewhere it shouldn't be. This is a strong indicator of a hidden leak.
Use a Portable Gas Detector
Battery-powered combustible gas detectors are available from hardware stores such as Bunnings or Mitre 10. Hold the sensor near wall sockets, skirting boards, pipe penetrations, and any gaps around gas pipe entry points. These devices detect elevated gas concentrations in the air and can help narrow down the location of a hidden leak — but they are a guide only, not a definitive diagnostic tool.
Important: Even if your checks come back negative, if you still smell gas or have other symptoms, call a licensed gasfitter. Gas can pool in pockets and be intermittent.
What a Licensed Gasfitter Will Do
Locating a hidden gas leak inside a wall properly requires specialist equipment and expertise. A licensed gasfitter may use:
- Electronic gas leak detectors — far more sensitive than consumer-grade units.
- Pressure testing — isolating sections of pipework and monitoring for pressure drop to pinpoint the leak location.
- Thermal imaging cameras — in some cases to detect temperature anomalies around leaking pipes.
- Tracer gas testing — injecting a safe tracer gas and using a detector to find exactly where it escapes.
Once found, the gasfitter will repair or replace the faulty section of pipe or fitting. In NZ, all gas pipework repair and installation is restricted work under the Gas Act 1992 and must be carried out by a gasfitter licensed by the Plumbers, Gasfitters and Drainlayers Board (PGDB). It is illegal for an unlicensed person to carry out this work, and doing so could void your home insurance.
When to Call a Professional
Call a licensed gasfitter immediately if:
- You can smell gas anywhere in or around your home.
- Your meter is moving with all appliances off.
- Your gas detector is alarming.
- Appliances are behaving erratically or pilot lights keep extinguishing.
- You have any doubt whatsoever.
Do not attempt to open walls, cut pipes, or repair fittings yourself — this is both dangerous and illegal. You can find qualified, local gasfitters on tradedirectory.co.nz to get the job done safely and legally.
The NZ Building Code sets out requirements for gas installations under Clause G10 (piped gas), and any remedial work must meet these standards. Your local council may also need to be notified depending on the scope of work — your gasfitter can advise you on this.
Safety Note
Gas leaks are one of the leading causes of house fires and explosions in New Zealand. Never ignore the smell of gas or delay calling for help. When in doubt, get out and call 111.