Gas Hot Water Pilot Light Won’t Stay Lit? How to Tell What’s Wrong (Sydney)

Your gas hot water pilot light won’t stay lit. You’ve tried relighting it once or twice, and it keeps dying. That’s frustrating, but it’s also telling you something specific.

The trick is reading the symptoms. A pilot light that won’t light at all is a different problem from one that lights but dies after ten seconds. A lazy yellow flame means something completely different from a clean blue flame that still won’t hold. Each symptom points to a different fault — and knowing which one you’re dealing with saves you time, money, and the runaround.

Here’s how to work through it like a diagnostic checklist, starting with what you’re seeing and narrowing it down from there.

What Exactly Is Happening?

Before you call anyone or start pulling panels off, take a minute to observe what the unit is actually doing. Your pilot light is giving you clues. You just need to know what to look for.

Ask yourself these four questions:

1. Does the pilot light at all when you try? If you press and hold the pilot button and click the igniter, does a flame appear — even briefly? Or is there nothing at all?
2. If it lights, how long does it stay lit? Does it die the instant you release the button? Does it hold for a few seconds and then fade? Or does it stay lit for hours and then go out on its own?
3. What colour is the flame? A healthy pilot flame is mostly blue with a small yellow tip. Is yours yellow, orange, flickering, or unusually small?
4. Can you smell gas? Before, during, or after trying to light the pilot — any rotten-egg smell near the unit?

Your answers to those four questions will point you toward one of the fault categories below. If the answer to number four is yes, skip everything else — turn off the gas at the meter, leave the area, and call the gas emergency line or 000 immediately.

Nothing Happens When You Try to Light the Pilot

You press and hold the pilot knob, click the igniter, and get absolutely nothing. No spark, no flame, no sound.

What this usually means

The igniter is dead. The piezo igniter — the button that makes the clicking sound — is a mechanical part that wears out. If you’re not hearing a click at all, or the click sounds weak and hollow, the igniter has failed. This doesn’t mean anything else is wrong with the unit. You can test this by using a long-reach lighter at the pilot opening while holding the gas knob down. If the pilot lights with a manual flame, your igniter is the problem.

The gas isn’t reaching the pilot. If you hear the click but get no flame even with a manual lighter, gas isn’t flowing to the pilot assembly. This could be a closed gas isolation valve (check the valve on the gas line leading to the unit — it should be parallel to the pipe, not perpendicular), a fault in the gas control valve inside the unit, or a broader gas supply issue. Check whether your gas cooktop or other gas appliances are working. If nothing in the house has gas, the issue is upstream — contact your gas supplier.

The pilot tube is blocked. The small tube that delivers gas from the control valve to the pilot burner can get clogged with dust, cobwebs, or corrosion. If gas is flowing to the unit but not reaching the pilot flame, a blocked tube is a likely cause. This needs a licensed gas fitter to disassemble and clear.

The Pilot Lights but Dies the Instant You Release the Button

This is the most common scenario we see across Sydney — Penrith, Parramatta, the inner west, right through to the Hills District. The pilot flame appears, it looks fine, but the moment you stop holding the button down, it goes out.

What this usually means

The thermocouple is failing. Nine times out of ten, this is your answer. The thermocouple is a thin metal probe that sits directly in the pilot flame. When the flame heats it, the thermocouple generates a tiny electrical current — millivolts — that tells the gas valve “the pilot is lit, keep the gas flowing.” When you hold the button down, you’re manually overriding the gas valve. When you release it, the valve relies on that thermocouple signal to stay open. If the thermocouple is worn out, degraded, or not positioned correctly in the flame, the signal is too weak and the valve snaps shut.

How to confirm it: If the pilot lights cleanly, burns blue, and looks perfectly healthy while you’re holding the button — but dies within one to three seconds of releasing — the thermocouple is almost certainly the fault. This is the textbook symptom.

A thermocouple replacement is one of the most common gas hot water repairs. It’s a straightforward job for a licensed gas fitter and one of the less expensive fixes on a gas system.

Less common but possible: The thermocouple could be physically displaced — knocked out of the flame path by vibration or previous work. If the probe tip isn’t sitting in the hottest part of the flame, it won’t generate enough voltage even if the part itself is fine. A gas fitter can check alignment in under a minute.

The Pilot Stays Lit for a While, Then Goes Out on Its Own

Different from symptom 2. Here, the pilot holds for minutes, hours, or even a day or two — then dies without anyone touching the unit.

What this usually means

Wind or draughts. This is common in Sydney homes where the hot water unit is installed on an exposed external wall, beside a side gate that funnels wind, under eaves, or near a garage door. If the pilot goes out during windy weather and relights perfectly fine afterwards, wind is your culprit. A draught guard or wind shield fitted around the burner compartment is the fix — simple and permanent.

Intermittent gas pressure drops. If the gas supply pressure fluctuates — dropping low enough that the pilot flame shrinks below the thermocouple tip — the valve reads it as “pilot out” and shuts off. This is harder to catch because the pressure might be fine when the gas fitter arrives. A gas fitter can install a pressure gauge to monitor over time, or test with a manometer during the visit. If your gas cooktop flame also seems weaker at certain times of day, that’s a strong clue.

A thermocouple on its last legs. Sometimes a thermocouple doesn’t fail completely — it hovers right on the edge. It generates enough voltage to hold the valve open when conditions are perfect, but any small fluctuation — a slight breeze, a minor gas pressure dip, the unit cooling down overnight — pushes it below the threshold and the pilot drops out. This intermittent pattern is the thermocouple slowly dying rather than failing all at once.

The Pilot Flame Is Yellow, Orange, or Flickering

You’ve got the pilot lit, and it’s holding. But the flame doesn’t look right.

What this usually means

A yellow or orange flame means incomplete combustion. A healthy pilot burns blue because the gas is mixing with the right amount of air and burning efficiently. When the flame turns yellow or orange, the gas-to-air ratio is off — typically not enough air reaching the burner. This produces carbon monoxide, which is colourless and odourless.

This is a safety issue. Don’t ignore it.

Causes include: a dirty or partially clogged pilot orifice restricting gas flow, dust or debris blocking the air intake around the burner compartment, or a damaged flue that’s affecting ventilation.

What to do: If your pilot flame is yellow or orange, do not leave the unit running. Turn the gas control to off and call a licensed gas fitter. Continuing to operate a unit with incomplete combustion puts your household at risk of carbon monoxide exposure, especially if the unit is in or near an enclosed space like a laundry or garage.

You Can Smell Gas Near the Unit

Rotten egg smell near the hot water system — whether the pilot is lit or not.

What this usually means

Natural gas is odourless on its own. The rotten egg smell is mercaptan, a chemical added by gas suppliers specifically so you can detect leaks. If you smell it, there may be a gas leak at or near the unit.

Do not try to relight the pilot. Do not use light switches, phones, or anything that could create a spark near the unit.

Do this instead:

1. Turn off the gas supply at the meter
2. Open doors and windows
3. Leave the property
4. Call the gas emergency line or 000 from outside

This is not a troubleshooting situation. This is a safety situation.

The Pilot Stays Lit but the Water Isn’t Hot

The pilot is burning fine. The unit looks like it’s working. But the water coming out of your taps is lukewarm at best.

What this usually means

The main burner isn’t firing. The pilot light’s job is to ignite the main burner when the thermostat calls for heat. If the pilot is lit but the main burner never kicks in, the thermostat may be faulty, the main gas valve may not be opening fully, or the burner itself may be blocked or corroded.

The thermostat is set too low or has failed. Check the temperature dial on the unit. If it’s turned down, try raising it. If it’s set correctly and the water is still lukewarm, the thermostat may have failed internally.

Sediment build-up in the tank. On storage gas hot water systems, sediment accumulates at the bottom of the tank over time. This layer sits between the burner and the water, reducing heating efficiency.

All three of these faults require a licensed gas fitter.

When You Can Relight It Yourself (and When to Stop)

Relighting the pilot is the one thing you can legally do yourself on a gas hot water system. Every unit has instructions printed on the front panel or inside the access door. Follow those specific steps for your model.

The general process:

1. Turn the gas control knob to OFF. Wait five full minutes.
2. Turn the knob to PILOT.
3. Press and hold the knob down.
4. While holding, click the igniter button.
5. Keep holding for 30 to 60 seconds.
6. Release the knob slowly. If the pilot holds, turn to ON.

The two-attempt rule: If the pilot won’t stay lit after two proper attempts, stop. Something is wrong internally. Call a licensed gas fitter.

Gas Work in NSW

In New South Wales, all gas fitting work must be carried out by a tradesperson holding a Gas Work Licence issued by NSW Fair Trading. All work must comply with AS/NZS 5601 (Gas Installations), and the gas fitter is legally required to issue a compliance certificate when the job is done.

• Unlicensed gas work is illegal under NSW legislation
• It voids your home insurance
• It voids the manufacturer’s warranty on the appliance
• It creates genuine safety risks — gas leaks, carbon monoxide, fire

What Does It Cost?

It depends on the fault. Different brands use different parts at different price points, and labour varies depending on access and complexity.

What we can tell you is this: we diagnose first, tell you what’s actually wrong, and give you a straight answer on cost before we start any work. If a repair doesn’t make sense on an older unit, we’ll say so.

Call us and tell us what’s happening — we’ll give you a straight answer.

Frequently Asked Questions

Why does my gas hot water pilot light go out when it’s windy?

Wind is one of the most common reasons a pilot light goes out, and it’s especially prevalent in Sydney suburbs where hot water units are installed in exposed positions. The pilot flame is small — a strong gust through a side gate, under eaves, or past a garage opening can blow it out.

How do I know if my thermocouple needs replacing?

The signature symptom of a failing thermocouple is a pilot light that ignites normally while you hold the button down but dies within one to three seconds of releasing it. The flame looks healthy, burns blue, and appears perfectly fine — but the moment you let go, it goes out.

Is a yellow pilot flame dangerous?

A yellow or orange pilot flame is a sign of incomplete combustion, and yes, it should be treated seriously. When gas burns completely, the flame is blue. When it burns incompletely — usually because the gas-to-air ratio is wrong — the flame turns yellow or orange.

Can a gas hot water pilot light problem cause carbon monoxide?

Yes, but it depends on the specific fault. The pilot light going out on its own does not produce carbon monoxide — it simply means the flame has extinguished and the gas valve has closed.

Should I repair or replace my gas hot water system?

This depends on the age of the unit, the nature of the fault, and how many times you’ve already had it repaired. As a general guide, if the unit is under ten years old and this is the first significant repair, fixing it usually makes sense. However, if the unit is over twelve years old and you’ve had two or more repairs in the past eighteen months, you’re likely spending money on a system that will keep failing.

What should I check before calling a plumber about my pilot light?

Before you call, run through a quick checklist that can save both you and your plumber time. First, check the gas supply — is the isolation valve on the gas line to the unit open? The handle should be parallel to the pipe, not perpendicular. Check whether other gas appliances in the house are working. If nothing has gas, the issue is upstream and you need your gas supplier, not a plumber. Second, try relighting the pilot using the instructions on the unit — follow them exactly for your model. Note what happens: does the pilot light at all? Does it hold while you press the button but die on release? Does it stay lit for a while and then go out? Third, look at the flame colour through the viewing window — is it blue, yellow, or orange? Fourth, note the age of the unit if you know it, and whether you’ve had previous repairs. Finally, check for any smell of gas around the unit. Giving your plumber these details over the phone helps them arrive prepared with the right parts and a clear idea of the likely fault.

Call Plumbing Paramedics

We’re licensed plumbers and gas fitters servicing Sydney — from the western suburbs through the inner west and beyond. If your pilot light won’t stay lit, your hot water has gone cold, or you want someone to properly diagnose what’s going on with your gas hot water system, give us a call.

We’ll tell you what’s actually wrong, what it’ll cost, and whether it’s worth repairing. No guesswork, no pressure.

Call Plumbing Paramedics — 0430-054-007 — or visit plumbingparamedics.com.au