Water Heater Pilot Light Won’t Stay Lit: Causes and Fixes

You wake up to a cold shower, check the water heater, and find the pilot light is out. Again. A pilot light that will not stay lit is one of the most common gas water heater problems, and it can be frustrating. The good news is that the cause is usually one of a few well-known issues, and some of them are fixable without a service call. Here is how to diagnose the problem and decide whether you need a professional plumber.

Key Takeaways

• A faulty thermocouple is the most common reason a pilot light will not stay lit. This $20 part tells the gas valve that the pilot is burning. When it fails, the valve shuts off gas as a safety measure.
• A dirty pilot tube can produce a weak flame that does not properly heat the thermocouple, causing it to shut off.
• Drafts from nearby vents or windows can blow out the pilot light, especially in garages and utility rooms.
• If you smell gas at any point, do not attempt repairs. Leave the house immediately and call your gas company.

How to Relight a Water Heater Pilot Light

Before diagnosing why the pilot keeps going out, try relighting it:

1. Turn the gas control knob to the OFF position. Wait 5 to 10 minutes for any residual gas to clear.
2. Turn the knob to the PILOT position.
3. Press and hold the pilot button (or knob) while using the built-in igniter or a long match to light the pilot.
4. Continue holding the pilot button for 60 seconds after the flame ignites. This heats the thermocouple enough to keep the gas valve open.
5. Release the button. The pilot should stay lit.
6. Turn the gas control knob to the ON position and set your desired temperature.

If the pilot lights but goes out as soon as you release the button, the thermocouple is the likely culprit.

Common Causes and Solutions

1. Faulty Thermocouple

The thermocouple is a safety sensor that detects the pilot flame. When it senses heat, it keeps the gas valve open. When it fails or weakens, it cannot keep the valve open, and the gas supply shuts off, killing the pilot.

Signs: The pilot lights when you hold the button but goes out within seconds of releasing it.

Fix: A thermocouple replacement costs $20 to $40 for the part and $100 to $200 for a professional service call. Handy homeowners can replace it themselves with basic tools by following the manufacturer’s instructions.

2. Dirty or Clogged Pilot Tube

The pilot tube delivers gas to the pilot light. If it is partially clogged with dust, spider webs, or debris, the flame will be small and yellow instead of a strong blue cone. A weak flame cannot properly heat the thermocouple.

Signs: The pilot flame is yellow, flickering, or very small.

Fix: Carefully clean the pilot tube opening with a thin needle or compressed air. If you are uncomfortable doing this, a plumber can clean it during a service visit.

3. Draft or Airflow Issues

A strong draft from a nearby window, door, vent, or dryer exhaust can blow out the pilot light. This is especially common when water heaters are located in garages or near exterior doors.

Signs: The pilot goes out intermittently, often during windy weather or when certain doors are opened.

Fix: Identify and seal the source of the draft. Consider adding a draft shield around the pilot area. Make sure the water heater area has proper ventilation without direct drafts on the burner assembly.

4. Failing Gas Control Valve

If the thermocouple tests fine and there are no draft issues, the gas control valve (thermostat) may be failing. This is the large knob assembly on the front of the water heater that controls the pilot, gas flow, and temperature.

Signs: Multiple components have been replaced but the problem persists.

Fix: Gas valve replacement costs $200 to $400 for the part alone plus labor. On older water heaters, it may be more cost-effective to replace the entire unit.

5. Flex Tube Issues

The flex tube carries gas from the control valve to the burner. If it is kinked, damaged, or not properly connected, it can restrict gas flow to the pilot.

Signs: Weak pilot flame, pilot will not light at all.

Fix: Inspect the flex tube for visible kinks or damage. If it looks compromised, have a plumber replace it.

When to Call a Professional

Some pilot light issues are DIY-friendly, but gas appliances demand respect. Call a licensed plumber if:

• You smell gas at any point during troubleshooting
• The pilot will not light at all (not just going out)
• You have replaced the thermocouple and the problem persists
• The water heater is making unusual sounds (banging, whistling)
• You see soot or scorch marks around the burner area
• Your water heater is more than 10 years old and experiencing multiple issues

Frequently Asked Questions

Is it dangerous if my pilot light goes out? Modern water heaters have safety mechanisms that shut off gas flow when the pilot goes out, preventing gas leaks. However, if you ever smell gas, leave the house immediately and contact your gas company. Do not flip switches or create sparks. We also provide expert service in Longmont and the surrounding St. Vrain Valley — visit our plumber in Longmont, CO page for details.

How much does it cost to fix a water heater pilot light? A thermocouple replacement (the most common fix) costs $100 to $200 for a professional service call. If the gas valve needs replacement, expect $300 to $500. A simple relighting costs nothing if you do it yourself.

Why does my pilot light keep going out in winter? Cold weather can increase drafts in garages and utility rooms, which blow out pilot lights. It can also cause condensation on the thermocouple, interfering with its function. Ensure your water heater area is draft-free and properly ventilated.

Should I upgrade to a water heater without a pilot light? Modern water heaters use electronic ignition systems instead of standing pilot lights. They are more energy efficient (no pilot gas consumption 24/7) and eliminate pilot light problems entirely. If your water heater is aging and giving you trouble, an upgrade may be the best investment.