A gas water heater with no hot water often comes down to a pilot light that’s out — sometimes a simple relight, sometimes a failing part that needs replacing.
Written bySteven Lockhart·Reviewed byMiguel Lopez, Owner & Licensed Plumber, New Pro Plumbing (CSLB #974600)·Last reviewedAugust 2026 · 8 min readQuick Answer
If your gas water heater’s pilot light is out, you can often relight it using the instructions printed on the unit. If it won’t stay lit, the usual cause is a failing thermocouple — the safety sensor that shuts off gas when it detects no flame. New Pro fixes pilot problems and replaces thermocouples fast across West LA. If you ever smell gas, leave and call from outside.
On a gas water heater, the pilot light is a small flame that ignites the main burner. If it goes out, the burner can’t fire and you lose hot water. A pilot can go out from a draft or a one-off, and relighting following the unit’s instructions solves those. But when a pilot won’t stay lit after relighting, the culprit is almost always the thermocouple.
Water heater pilot light out — Water heater pilot light repair is the relighting of a gas water heater’s pilot and the diagnosis and replacement of the components — usually the thermocouple — that keep it from staying lit.
The thermocouple is a safety sensor — it detects the pilot flame and shuts the gas off if it doesn’t, and when it weakens it shuts the gas off even with the pilot lit, which is exactly the kind of repair an emergency plumber handles quickly.
A draft or a temporary interruption can blow out a pilot — relighting per the unit’s label often fixes it.
A pilot that dies again right after relighting almost always needs a new thermocouple.
Follow the unit’s own instructions — and stop if you smell gas.
If you smell gas, don’t relight — leave and call from outside.
Follow the lighting instructions printed on your unit.
Turn the gas control to ‘pilot’ and wait for gas to clear.
Ignite the pilot and hold the control per the instructions.
If it goes out when you release, the thermocouple is likely failing.
We replace the thermocouple and restore hot water.
Relit and still no hot water? The issue may be beyond the pilot — see no hot water or water heater repair for the other causes; if it’s also leaking, see a leaking water heater.
Pilot won’t stay lit? It’s usually a quick thermocouple fix — call us.
Get a Free QuoteThe pilot light system is a good example of how a water heater builds safety in. The thermocouple exists precisely so that gas can never flow unless there’s a flame to burn it — if the pilot goes out, the gas shuts off automatically. That’s why a failing thermocouple, frustrating as it is, is actually the safety system doing its job a little too eagerly: it errs on the side of shutting the gas off. Replacing it restores normal function without defeating the protection.
That built-in caution is also why gas water heaters deserve respect. A one-time relight is routine, but a persistent pilot problem, a weak or yellow flame, or any smell of gas moves the situation out of DIY territory. Yellow flames and soot can indicate incomplete combustion, and gas odor can mean a leak — neither is something to troubleshoot by trial and error. When in doubt, the safe move is to stop and call. For efficiency questions on any eventual replacement, the ENERGY STAR program from the U.S. EPA and DOE is a useful reference.
We handle pilot and gas-valve work as licensed professionals for exactly this reason. Our work can be verified with the CSLB (#974600), and where a repair rises to a replacement or gas-line work, it’s permitted through the Los Angeles Department of Building & Safety and installed to code. A pilot fix is usually small and quick — but the gas system around it is one to treat with care.
Whether the pilot holds after relighting tells us most of what we need.
| Behavior | Likely cause | Fix |
|---|---|---|
| Relights and holds | Draft / one-off | Done |
| Dies after relighting | Failing thermocouple | Replace part |
| Won’t light / gas smell | Gas or valve issue | Stop — call us |
If it’s a thermocouple or a gas-valve issue, we fix it safely and flat-rate — that’s how 24/7 emergency plumbing should work.
A thermocouple is an inexpensive part, so a pilot that won’t stay lit is usually one of the more affordable water heater repairs — mostly the part and the labor to replace it. Costs only rise if the gas valve or another component is involved. We diagnose the specific cause and quote it flat-rate, and if a relight is all it needs, we’ll tell you that too.
Small job, honest price — see how our emergency plumbing service quotes flat-rate.
A homeowner relights the pilot each morning only to find it out again by evening, and the hot water keeps disappearing.
New Pro identifies a worn thermocouple, replaces it, and confirms the pilot holds and the burner fires.
The pilot stays lit for good, hot water is reliable again, and it was an inexpensive part-and-labor fix.
The Bottom Line
A pilot light out is usually a small problem — a relight, or an inexpensive thermocouple. The one rule that matters: if you smell gas, don’t touch anything, leave, and call from outside. Otherwise, a pilot that won’t stay lit is a quick, affordable fix that gets your hot water back.
The most common reason a pilot won’t stay lit is a failing thermocouple — the safety sensor that detects the pilot flame. When it weakens, it can no longer confirm the flame and shuts the gas off, so the pilot dies moments after you release the control. Other causes include a draft reaching the pilot, a dirty pilot orifice, or a gas supply issue. If relighting doesn’t hold, the thermocouple is the usual fix.
Follow the lighting instructions printed on a label on your specific unit, since the exact steps vary. Generally, you turn the gas control to ‘pilot,’ wait several minutes for any gas to clear, then ignite the pilot while holding the control down for the time the instructions specify before releasing. Crucially, if you smell gas at any point, stop, leave the area, and call from outside — don’t attempt to light anything until it’s been checked.
A thermocouple is a small safety device that sits in the pilot flame and generates a tiny electrical current from the heat. That current tells the gas valve the pilot is lit and keeps the gas flowing; if the flame goes out, the current stops and the valve shuts the gas off. Over years of sitting in a flame, the thermocouple degrades and eventually can’t produce enough current, so the valve shuts the gas off even with the pilot burning. It’s a cheap, common replacement.
For a straightforward relight following the unit’s instructions, many homeowners can do it safely. The one firm exception is gas odor: if you smell gas, do not attempt to relight anything — leave the home and call from outside, because attempting ignition with gas present is dangerous. Also, if the pilot won’t stay lit after relighting, don’t keep forcing it; that points to a component that needs professional replacement rather than repeated relighting.
Treat it seriously. Don’t light anything, don’t operate electrical switches, and don’t look for the source yourself. Leave the home, and from a safe location outside call your gas utility’s emergency line and a licensed plumber. A gas smell around a water heater can indicate a leak at the supply or valve, and it needs to be checked before the unit is used again. Safety first — the pilot can wait until it’s confirmed safe.
Written by the New Pro Plumbing content team and reviewed for technical accuracy by Miguel Lopez, owner and California-licensed plumber (CSLB #974600). Guidance follows U.S. EPA, CSLB, and LADBS sources where cited. Any figures reflect New Pro Plumbing's flat-rate practice and West LA conditions, not a quote — we confirm pricing in writing before any work begins.
Last reviewed: August 2026.
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