The pilot light on a gas water heater should stay lit reliably, delivering hot water when needed. When it won’t stay on, it can indicate a safety concern or a maintenance issue that requires attention. This guide explains the common causes, step-by-step diagnostics, and practical fixes you can perform safely. It covers issues related to the thermocouple, gas valve, venting, and sediment buildup, along with guidance on when to call a professional. By understanding the root causes, homeowners can restore hot water efficiently while avoiding unnecessary repairs.

Common Causes Of A Pilot Light That Won’t Stay On

The following issues frequently cause a pilot light to go out and fail to stay lit. Some are simple maintenance tasks, while others require professional service.

Thermocouple misalignment or damage: The thermocouple detects heat from the pilot flame. If it’s dirty, bent, or failing, it can shut off gas to the burner prematurely.
Dirty or blocked pilot orifice: Dust or debris can obstruct the flame, causing instability that leads to shutdowns.
Gas valve or regulator problems: A faulty gas valve may intermittently cut gas supply or fail to maintain pressure, turning the pilot off.
Drafts or venting issues: Incoming air or poor venting can blow out the pilot or create unstable combustion.
Sediment buildup in the tank: Sediment can affect burner performance and flame stability, especially in older units.
Faulty or dirty thermostat (on electric or indirect systems): If a non-gas component is involved, a malfunctioning thermostat can affect ignition controls.
Gas supply problems: Low or fluctuating gas pressure from the line can cause the pilot to extinguish.

Initial Safety Checks And Preparations

Before performing any troubleshooting, ensure you follow essential safety steps. If you smell gas or notice a strong rotten-egg odor, evacuate and call the gas utility or emergency services. If you’re comfortable, turn off the gas supply to the heater and allow any residual gas to dissipate before inspecting components.

Diagnostic Steps To Identify The Cause

Use these non-invasive steps to diagnose common issues. If a step seems risky, stop and contact a professional.

Inspect the thermocouple: Look for visible damage or bending. The thermocouple should be vertical and in contact with the pilot flame. Clean with a soft cloth and recheck alignment. If damaged, replacement is often required.
Clean the pilot assembly: With the gas off, remove the access panel and gently clean the pilot orifice and surrounding area with a soft brush or compressed air. Do not use metal tools that could damage parts.
Check the flame quality: A healthy pilot flame should be blue with a small yellow tip. A weak, flickering flame can indicate gas supply issues or dirty passages.
Test gas supply: Ensure the gas valve is fully open and the gas line is delivering steady pressure. If you suspect supply issues, contact the gas utility or a licensed plumber.
Inspect venting and drafts: Ensure the area is free of drafts from nearby fans, windows, or doors. Check the vent terminal on the roof or wall for obstructions.
Look for sediment buildup: In older tanks, sediment can affect burner performance. Consider flushing the tank if sediment has accumulated excessively.

Step-By-Step Fixes For A Pilot Light That Won’t Stay On

These fixes address the most common culprits. If a fix requires disassembly or complex gas work, consider professional service to avoid safety risks.

Realign or replace the thermocouple: If the thermocouple is bent or not properly seated in the flame, adjust or replace it. Replacement is typically quick and inexpensive.
Clean or replace the pilot assembly: Clean the orifice and ensure the pilot flame is properly positioned on the thermocouple tip. Replace the pilot assembly if corrosion or damage is present.
Clean or replace the gas control valve or regulator: A faulty valve or regulator can cause intermittent flame failure. A professional may need to replace these components.
Address venting and drafts: Seal gaps around the heater, install or repair venting, and move sources of drafts away from the unit.
Flush sediment from the tank (if applicable): For tanks with significant sediment, draining and flushing can improve burner performance and flame stability.
Ensure proper gas pressure: If pressure is outside the recommended range, a licensed technician should adjust or replace the regulator to restore stable operation.
Inspect safety shutoff mechanisms: Some units have additional safety features that can trip if a fault is detected. A professional can diagnose and reset them safely.

When To Call A Pro

Some issues require professional expertise due to safety concerns and code compliance. Contact a licensed plumber or gas technician if any of the following apply: persistent flame instability after cleaning, suspected gas pressure problems, persistent gas odor, pilot light relighting requires repeated manual ignition, or you hear hissing from the gas line.

Prevention Tips To Keep The Pilot Light Reliable

Preventive maintenance helps avoid future pilot outages and extends the life of the water heater. Regular checks can save energy and reduce repair costs over time.

Schedule annual professional maintenance: A technician can inspect the burner, thermocouple, venting, and gas lines for wear and corrosion.
Keep the area clear: Maintain at least 18 inches of clearance around the heater to promote safe combustion and easy access.
Test the igniter and flame regularly: Run hot water periodically to ensure the unit cyles correctly and the flame remains stable.
Address drafts promptly: Install weatherstripping around doors and windows near the heater to minimize drafts that can extinguish the pilot.
Use high-quality gas supply: If you notice fluctuating flame strength, discuss gas supply quality with your utility or technician.
Replace aging components: If the heater is several decades old, plan for component upgrades or a full replacement to improve reliability and efficiency.