The sight of a standing pilot light on a gas water heater is reassuring, but when the burner refuses to ignite while the pilot remains lit, household comfort is disrupted. This guide explains common causes, safe troubleshooting steps, and remedies to help homeowners diagnose and fix a water heater that has a pilot light but no burner. It emphasizes safe handling, practical checks, and knowing when to call a licensed technician.

Symptoms And Common Causes

When the pilot light stays on but the burner does not ignite, typical symptoms include: the thermostat calling for heat but the burner not lighting, a lack of hot water despite a lit pilot, or a burner that ignites briefly and then goes out. The underlying issues often involve fuel supply, ignition components, or safety interlocks. Understanding these categories helps narrow the cause quickly.

Thermocouple or flame sensor problems: A faulty thermocouple or dirty flame sensor can fail to signal that the pilot flame is present, preventing the main burner from lighting.
Gas control valve or main gas supply: If the valve isn’t opening correctly or the gas supply is insufficient, the burner may not ignite.
Icing or obstruction in the burner or pilot tube: Debris, spider webs, or mineral buildup can block gas flow to the burner.
Thermostat or control board issues: A malfunctioning thermostat may not send the correct signal to ignite the burner.
Ventilation or safety switch problems: A blocked vent or faulty high-limit switch can prevent ignition for safety reasons.

Safety First

Gas appliances pose fire and carbon monoxide risks. If you smell gas, hear a hissing sound, or suspect a gas leak, evacuate and call the utility company or emergency services. Do not attempt to operate electrical switches or create sparks. Before performing any inspection, ensure the area is well ventilated and the gas supply is shut off if you suspect a leak.

Initial Quick Checks

Begin with these safe, low-effort checks to determine if a simple fix is available:

Confirm pilot is lit: If the pilot flame is weak or yellow, shut off gas, wait five minutes, and relight following the manufacturer’s instructions.
Look for obviously blocked components: Inspect the burner and pilot tube for dirt, spider webs, or debris and clear carefully with a soft brush or compressed air.
Check the thermocouple: A bent or loose thermocouple can fail to sense flame. Ensure it extends into the pilot flame and is properly aligned.
Inspect the gas valve: Ensure the gas shutoff valve is fully open. A partially closed valve can limit gas flow to the burner.
Reset the system: Some units have a reset or high-limit switch. If safe, perform a reset following the manual, then attempt to ignite again.

In-Depth Troubleshooting Steps

For persistent issues, follow these more detailed steps. If any step requires tools or involves gas handling beyond your comfort level, call a licensed technician.

Test the thermocouple circuit: With the pilot lit, measure the thermocouple output if you have access to the sensor wiring. A defective thermocouple may require replacement.
Inspect and clean the burner orifice: Remove the burner access panel and inspect the orifice for obstructions. Use a small brush or compressed air to clean. Do not enlarge the hole.
Verify the pilot flame quality: A weak or irregular pilot flame can fail to heat the thermocouple adequately. If the pilot flame is unstable, reignite per the manual and observe changes.
Evaluate the gas control valve: Some models have diagnostic indicators or a test port. If the valve shows signs of wear or fails to actuate, replacement may be necessary.
Check limit and safety switches: A tripped high-limit switch or failed pressure switch can prevent ignition. Reset if safe, and replace faulty switches.
Thermostat calibration: A miscalibrated thermostat can prevent ignition despite a ready burner. Test by setting to a higher temperature and see if ignition occurs.

When To Call A Pro

Despite best DIY efforts, some situations require professional service. Consider calling a licensed plumber or HVAC technician if:

Gas smells persist or leaks are suspected: This is a safety emergency.
The thermocouple, gas valve, or ignition system shows signs of damage or wear: Replacement tasks should be performed by a professional.
Repeated resets do not restore ignition: A persistent fault indicates a deeper issue with gas control or safety interlocks.
Water heater is old or under warranty: A pro can assess efficiency, safety, and cost-effective replacement options.

Preventive Maintenance And Prolonged Reliability

Regular maintenance can reduce the likelihood of pilot-light-and-no-burn issues. Recommended practices include:

Annual professional inspection: A yearly check helps identify wear on the thermocouple, gas valve, and burner orifice.
Keep vents clear: Ensure exhaust vent paths are unobstructed to prevent safety shutoffs.
Clean pilot and burner assemblies: Periodic cleaning minimizes buildup that inhibits ignition.
Test the thermostat and controls: Verifying proper operation ensures the burner engages when heat is needed.
Flushing mineral deposits: In hard-water areas, periodic flushing can improve efficiency and reduce buildup that affects ignition components.

Product And Model Variations

Gas water heaters come in standing-pilot and electronic ignition designs. Some newer units use intermittent electronic ignition or hot-surface igniters, which change the troubleshooting approach. Always consult the user manual for model-specific procedures, safety warnings, and replacement parts compatibility. For older units, consider energy-efficiency upgrades or gas line assessments to ensure safe operation and cost-effective performance.

FAQs

Q: My pilot light stays on but the burner won’t ignite. What’s first? Check for a dirty thermocouple, a partially closed gas valve, or a blocked burner orifice. Clean or adjust as needed, then attempt ignition again.

Q: Can I relight the pilot if it goes out? Yes, but only after locating the reason for the outage. Follow the manufacturer’s relighting procedure and wait for any gas to dissipate before attempting again.

Q: Is maintenance worth it for a standing-pilot water heater? Absolutely. Regular maintenance reduces failure risk, improves efficiency, and extends unit life.