Written by JSW Plumbing | Published on July 2025
A gas leak in your home will often announce itself through a strong sulphur or rotten egg smell, a hissing sound near appliances or pipes, or unexplained physical symptoms like dizziness and nausea. This article covers every major warning sign, what to do if you spot one, and how homeowners in Thornleigh and the broader Hills District can stay safe.
Recognise the Most Common Warning Signs of a Gas Leak
Natural gas is odourless in its pure form, so gas suppliers add a chemical called mercaptan to give it that distinctive rotten egg or sulphur smell. That smell is your first and most important clue.
Beyond the smell, there are several other signs you should never ignore. Catching any one of these early can prevent a dangerous situation from escalating.
- Rotten egg or sulphur smell inside the home or near appliances
- Hissing or whistling sounds coming from gas lines, meters, or appliances
- Dead or yellowing vegetation in patches above buried gas lines outside
- Bubbling in standing water near your gas meter or garden
- Visible damage to gas pipes, connectors, or flexible hose connections
- Higher than usual gas bills with no change in usage habits
- Pilot lights that keep going out on your stove, hot water system, or heater
If you notice more than one of these signs at the same time, treat the situation as an emergency and act immediately.
Identify Physical Symptoms That Point to Gas Exposure
Sometimes a gas leak is slow and the smell is faint. In these cases, physical symptoms in the people or animals living in the home can be the first real clue something is wrong.
Low-level gas exposure affects your body before you might even notice an obvious smell. These symptoms tend to ease when you go outside and return when you come back indoors.
- Headaches that seem to appear at home but ease outside
- Dizziness, lightheadedness, or feeling faint indoors
- Nausea or an upset stomach without an obvious cause
- Fatigue or difficulty concentrating while at home
- Eye or throat irritation, particularly in poorly ventilated rooms
- Pets acting unusually lethargic or distressed indoors
If multiple people in your household are experiencing these symptoms at the same time, evacuate and call your gas supplier or emergency services straight away. Do not wait to confirm a smell.
Understand Which Appliances and Areas Carry the Highest Risk
Gas leaks do not happen randomly. They tend to occur at connection points, near ageing appliances, or where pipes have been disturbed. Knowing the higher-risk areas in your home helps you stay alert.
| Location or Appliance | Common Cause of Leak | Risk Level |
|---|---|---|
| Gas stove or cooktop | Worn burner seals or loose flexible hose | High |
| Gas hot water system | Corroded fittings or faulty pressure relief valve | High |
| Gas heater or furnace | Cracked heat exchanger or loose flue connection | High |
| Gas meter and regulator | Physical damage or aged components | Medium |
| Buried supply lines | Ground movement, tree roots, or excavation nearby | Medium |
| Flexible connector hoses | Kinking, age deterioration, or incorrect installation | High |
In the Hills District and Thornleigh area, older homes with original gas infrastructure from the 1970s and 1980s are more likely to have aged connectors and fittings that need inspection. JSW Plumbing regularly services these properties and knows the common failure points in local homes.
Know What to Do the Moment You Suspect a Gas Leak
Acting quickly and correctly can make the difference between a close call and a serious incident. The steps below are the accepted safe response in Australia, including here in New South Wales.
- Do not turn any switches on or off. Electrical sparks can ignite leaking gas.
- Do not use your phone inside the building. Step outside first before making any calls.
- Open windows and doors as you move through the space to ventilate quickly.
- Turn off your gas meter at the isolation valve if you can safely reach it.
- Evacuate everyone including pets, and move well away from the building.
- Call your gas distributor (Jemena in greater Sydney) on 131 909 for emergencies.
- Call 000 if you believe there is immediate danger, fire risk, or someone is unwell.
- Contact a licensed gas fitter like JSW Plumbing to inspect and repair before re-entering.
Never re-enter the building until a qualified gas fitter has inspected the property and confirmed it is safe. This is not a job for a DIY fix.
Compare Gas Leak Detection Methods Available to Homeowners
There are a few practical ways to check for a suspected leak before a tradesperson arrives. Some of these are safe for homeowners to try, while others require a licensed professional.
| Detection Method | Who Can Use It | How Reliable | Notes |
|---|---|---|---|
| Smell test | Homeowner | Good for obvious leaks | May not detect very slow leaks |
| Soapy water on fittings | Homeowner (minor checks only) | Moderate | Bubbles form at leak point |
| Gas detector alarm | Homeowner | Very good | Install near appliances, replace every 5-7 years |
| Pressure test | Licensed gas fitter only | Highly accurate | Required by Australian Standards AS/NZS 5601 |
| Electronic gas analyser | Licensed gas fitter only | Highly accurate | Detects very small concentrations |
Installing a gas detector alarm is one of the most practical steps any Hills District homeowner can take. They are inexpensive, widely available, and can alert you to a leak long before the smell becomes obvious.
For any confirmed or strongly suspected leak, always call a licensed gas fitter. In New South Wales, all gas work must be carried out by a licensed contractor under the Gas and Electricity (Consumer Safety) Act 2017.
Understand Why Thornleigh and Hills District Homes Need Regular Gas Checks
Homes across Thornleigh, Hornsby, and the broader Hills District were built across many decades. A large number of properties in the area still have original gas infrastructure that has never been formally inspected or pressure tested.
Local factors that increase risk in this area include:
- Older homes in Thornleigh and Hornsby with 40 to 50-year-old flexible connectors
- Tree root activity from large gum trees disturbing buried gas lines
- Significant ground movement during dry summers affecting pipe joints
- Renovations that disturb gas lines without proper re-testing afterwards
- Pool or landscaping excavation cutting into unmarked buried supply lines
JSW Plumbing works across Thornleigh, Hornsby, and the Hills District every week. Our team is licensed for gas fitting work in NSW and can carry out full gas safety inspections on residential properties. A routine check takes around 60 to 90 minutes and gives you a clear picture of the condition of your gas system.
We recommend homeowners book a gas safety inspection every 2 years, or after any renovation, property purchase, or incident that could have disturbed gas pipework.
FAQs on Signs of a Gas Leak in Your Home
How do I know if I have a small gas leak that is hard to smell?
Small or slow leaks may not produce a strong smell. Look for unexplained physical symptoms like recurring headaches or fatigue at home, pilot lights that keep going out, or a gas bill that has crept up without explanation. A gas detector alarm is the most reliable way to catch low-level leaks early.
Is it safe to stay in my house if I smell gas?
No. If you can smell gas inside your home, you should ventilate and evacuate immediately. Do not use light switches, appliances, or your phone while still inside. Move outside, then call your gas distributor or 000 if the situation feels urgent.
Can I fix a gas leak myself in NSW?
No. Under NSW law, all gas fitting work must be performed by a licensed gas fitter. Attempting to repair a gas leak yourself is illegal and extremely dangerous. Always call a licensed professional like JSW Plumbing to inspect and carry out any repairs.
How much does a gas leak inspection cost in the Hills District?
A residential gas safety inspection in the Thornleigh and Hills District area typically costs between $150 and $300 depending on the size of the property and the complexity of the gas system. This is a small investment compared to the risk of an undetected leak. Contact JSW Plumbing for an accurate quote.
How often should I get my gas appliances serviced in NSW?
Most gas appliance manufacturers and NSW safety guidelines recommend servicing gas appliances every 2 years for residential use. Hot water systems, heaters, and cooktops that see heavy daily use may benefit from annual checks. Your licensed gas fitter can advise based on the age and condition of your appliances.
What does a gas leak smell like exactly?
Natural gas itself is odourless, but the added mercaptan chemical gives it a strong smell often described as rotten eggs or sulphur. Some people also describe it as a slightly sweet chemical smell. If you notice anything unusual and out of place near your appliances or gas meter, take it seriously and investigate.
Wrap Up and Next Steps
Gas leaks can be subtle or obvious, but the consequences of ignoring the signs are serious. Knowing what to look for, whether that is a smell, a physical symptom, or a behavioural change in your household, gives you a real advantage in keeping your family safe.
If you live in Thornleigh, Hornsby, or the Hills District and want peace of mind about your home gas system, JSW Plumbing is here to help. Our licensed gas fitters can inspect your system, test for leaks, and carry out any repairs to Australian Standards.
Call JSW Plumbing today to book a gas safety inspection or to speak with one of our team about any concerns you have. Do not wait until a problem becomes an emergency.
