The shower runs cold, nothing has changed, and the unit outside looks exactly as it did yesterday. Gas hot water systems fail in a handful of predictable ways, and a few of them you can rule out in five minutes.
Before anything else: if you can smell gas near the unit, don’t touch switches or use your phone nearby. Move away from the area and call the gas emergency line on 131 909 from a safe distance.
- The pilot light has gone out The most common cause on older storage units.
- No gas reaching the unit A valve turned off, or an empty bottle on LPG.
- A failed sensor The part that proves the pilot is lit has stopped working.
- A continuous flow fault Newer units show an error code on the panel.
- Water, not gas Sometimes it’s a valve or the plumbing rather than the heater.
Most of the cold shower callouts we get across Kingsgrove and the wider St George area come down to one of those five, and the first two are worth checking before you pick up the phone.
Quick answer:
A gas hot water system that stops heating usually has no gas reaching it, a pilot light that’s gone out, or a failed sensor that keeps the gas shut off for safety. On continuous flow units, an error code on the panel points straight at the fault. Check whether your other gas appliances still work, because that tells you immediately whether the problem is the supply or the unit. Call a licensed gas fitter if the pilot won’t stay lit, if the unit is showing an error, or if there’s any smell of gas, in which case move away first and call 131 909.
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What stops a gas hot water system working
A gas water heater has to do three things: receive gas, ignite it, and keep burning safely. If any one fails, a safety device shuts the unit down rather than letting it run badly.
- The pilot light out Wind, a gas interruption or a dirty pilot assembly can extinguish it.
- A failed thermocouple The sensor that proves the pilot is lit, so gas keeps flowing.
- No gas supply An isolation valve closed, or an LPG bottle that has run empty.
- An ignition fault On continuous flow units, electronic ignition can fail to fire.
- A failed valve or thermostat The unit has gas and ignition but won’t heat properly.
Two quick distinctions help. If the hot water is lukewarm rather than cold, the unit is working but something is limiting it, often a thermostat or a mixing valve. If it’s stone cold at every tap, the unit has stopped altogether.
How we check a gas hot water system
We start at the supply and work forward: gas reaching the unit, then ignition, then how it’s burning and venting once it runs.
| Method | Best for |
|---|---|
| Hot water systems | Storage and continuous flow units |
| Gas fitting | Supply, burners and pilots |
| Gas repairs | Ignition and component faults |
| Emergency plumbing | Leaking or failed units |
A unit a few years old that has stopped suddenly is usually a repair. One over a decade old, struggling to hold temperature and now failing to light, is a different conversation, and we’ll tell you honestly which one you’re in.
What affects the price?
It depends on whether the unit needs a service, a part or replacing, and whether parts are still available for that model. We confirm the price after an inspection, before any work starts.
| What’s blocked | What affects the price | What’s usually needed |
|---|---|---|
| Pilot light out | Unit type and access | Gas appliance service |
| Pilot won’t stay lit | Part availability and unit age | Gas repairs |
| An error code showing | Which fault code and unit model | Continuous flow repair |
| Lukewarm water only | Thermostat or valve condition | Hot water repair |
| An old unit failing | Age and replacement options | Repair or replace advice |
When to stop and make the call
Everything on the safe list is outside the appliance. Anything involving the burner, the flue or the gas connection needs a licensed gas fitter, and in NSW that isn’t optional.
Safe to try yourself
- Check whether other gas appliances work
- Check the isolation valve is turned on
- Check the LPG bottle isn’t empty
- Note any error code on the display
- Check whether water is cold or just lukewarm
Stop and make the call
- The pilot won’t stay lit
- The unit shows an error code
- Water is pooling under the unit
- There’s no hot water at any tap
- You can smell gas at any point
One thing to skip:Don’t keep relighting a pilot that won’t stay lit. It goes out because a safety device is doing its job, and repeated attempts release gas each time. If you can smell gas, don’t use switches or your phone near the unit. Move away and call 131 909.
The bottom line
Two checks separate most of these problems. If your other gas appliances work, the supply is fine and the fault is in the unit. If the water is lukewarm rather than cold, the unit is running and something is limiting it.
Past that, gas work needs a licensed gas fitter in NSW, and there’s a reason for it. The safety devices that shut a unit down are protecting you from something, so the useful response is finding out what, rather than getting it running again at any cost.
No hot water? Let’s get it sorted
Water Workx Plumbing looks after homes across Kingsgrove and the wider St George area, with 24/7 emergency service when you need it. We’ll find out what’s gone wrong, explain it in plain English and give you a fixed price before any work starts. Call Peter and the team.
Gas Hot Water FAQs
Why has my gas hot water stopped working?
Usually the pilot light has gone out, gas isn’t reaching the unit, or a safety sensor has failed and shut it down. Checking your other gas appliances tells you which.
Why won’t the pilot light stay lit?
Most often a failed thermocouple, the sensor that proves the pilot is burning. Without that signal the unit cuts the gas, which is exactly what it should do.
Can I relight the pilot myself?
Some units have instructions on them for this. If it goes out again, stop and call a gas fitter, because repeated relighting of a failing unit releases gas each time.
Water Workx Plumbing is fully licensed and insured, available 24/7 for emergency plumbing, with clean and tidy workmanship, upfront pricing and a lifetime labour guarantee.
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