Water heater pilot light won't light: causes, a safe relight, and when to call
A gas water heater with no hot water and a pilot that won't light is one of the most common no-heat calls — and one of the few you can sometimes fix yourself safely. The usual culprits are a failing thermocouple (the safety sensor that shuts off gas when the pilot is out), an interrupted gas supply, or a venting and draft problem. This guide gives the symptom-to-cause map, a safe step-by-step relight, and the clear line where DIY stops: if you smell gas, you stop and follow the gas-leak steps. It also covers when a pilot that keeps failing means the heater itself is at end of life.
Last reviewed: 2026-06-06
Why won't my water heater pilot light stay lit?
The most common reason a gas water heater pilot won't stay lit is a failing thermocouple — the sensor that detects the pilot flame and shuts off gas when it can't. Other causes are an interrupted gas supply, a dirty pilot orifice, air in the gas line after service, or a venting and draft problem blowing the flame out.
The thermocouple is a safety device: when the pilot is burning, it heats the thermocouple, which signals the gas valve to stay open. When the thermocouple fails or is dirty, the valve reads 'no pilot' and shuts the gas off — so the pilot lights, then dies the moment you release the button.
Work through the symptom table below before touching anything. If at any point you smell gas — a rotten-egg odor — stop, leave, and follow the gas-leak steps in the last section. The relight is only for a pilot that has simply gone out, not for a suspected leak.
Common gas water-heater pilot symptoms. If you smell gas at any point, stop and follow the gas-leak steps below.
How to relight a water heater pilot safely
Turn the gas control to 'Off' and wait five minutes for any gas to clear, set it to 'Pilot,' hold the igniter or a long lighter to the pilot while pressing the control knob, hold for 30 to 60 seconds after the flame catches, then release and turn the control to 'On.' If it won't stay lit after two attempts, stop — the thermocouple or valve likely needs service.
The five-minute wait matters: it lets any unburned gas dissipate before you introduce a flame. Skipping it is how a simple relight becomes dangerous. Follow the instructions printed on the heater's label, which are specific to your model.
If the pilot still won't hold after two careful attempts, the part has failed and forcing it won't help. That is a repair call, not a relight — see our Bellevue water heater repair: tank, tankless, and heat-pump page.
Thermocouple, gas valve, or venting — narrowing it down
If the pilot dies the instant you release the knob, suspect the thermocouple first. If it stays lit at the pilot but the burner won't fire for hot water, suspect the gas valve or control. If the pilot keeps blowing out or you see soot, suspect venting and draft — which is a safety issue, not a DIY fix.
A thermocouple is an inexpensive part and the most common fix, but replacing it correctly means draining pressure, accessing the burner assembly, and reassembling to a gas-tight seal — which is why many homeowners have it done. A failing gas valve is a larger repair that sometimes tips the repair-or-replace decision toward replacement.
If the symptom is no hot water generally rather than a dead pilot specifically, work through our no hot water troubleshooting tree and water heater not heating: causes and fixes.
When to stop and call — and when to replace
Stop immediately and call from outside if you smell gas, see soot, or suspect a venting problem — those are safety faults, not relights. And if the heater is over 10 to 12 years old and the pilot keeps failing, factor a replacement into the decision rather than repeating repairs on a unit near end of life.
A gas smell is never a troubleshooting step. Leave the house, don't touch switches, and follow our guide on what to do when you smell gas in Bellevue, or call our 24-hour and 24/7 emergency plumber in Bellevue, WA once you're safely outside.
If the heater is aging and the pilot is one of several issues, weigh repair against replacement — the cost comparison is in tankless water heater cost in Bellevue, which covers tank and heat-pump options too.
Sources
Every fact in this guide cites a verifiable public source. If you find a number we got wrong, email dispatch@bellevueplumberpro.com.
- U.S. Department of Energy — Water heating
- U.S. Consumer Product Safety Commission — Gas appliance safety
- Puget Sound Energy — Natural gas safety
Need help with this in your home? See our Bellevue water heater repair: tank, tankless, and heat-pump page for pricing, our diagnostic process, and how same-day service works across the Eastside.
We dispatch for this across Crossroads, Lake Hills, and Factoria — see your neighborhood page for local response times and recent jobs.
Related services: Leak Detection and Pipe Repair.
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