Water Heater Pilot Light Keeps Going Out
Updated February 25, 2026
Gas water heater pilot light goes out repeatedly -- caused by a failed thermocouple, dirty pilot orifice, drafts, or a failing gas valve. This is typically a diy or pro fix. Estimated cost: $5 - $15 DIY (thermocouple); $150 - $300 for gas valve replacement.
Overview
A pilot light that goes out once is annoying. A pilot that goes out every few hours or days means a part has failed. The thermocouple is the cause 80% of the time -- it is a $5-$12 part and a 10-minute replacement. The remaining 20% is split between a dirty pilot orifice, drafts blowing the flame out, and a failing gas valve. Work through them in order and you will find the problem without guessing.
Symptoms
- No hot water -- pilot light is out when you check
- Pilot relights but goes out within seconds of releasing the control knob
- Pilot relights and stays on for hours or days, then goes out again
- Pilot flame is small, yellow, or flickering instead of a steady blue cone
- Gas control knob will not stay depressed in the PILOT position
Common Causes
- Failed thermocouple -- the safety sensor in the pilot flame has worn out and no longer signals the gas valve to stay open
- Thermocouple not positioned correctly in the pilot flame -- tip is beside the flame instead of in it
- Dirty or clogged pilot orifice -- produces a weak flame that does not heat the thermocouple sufficiently
- Draft from nearby vents, windows, or HVAC registers blows the pilot out intermittently
- Failing gas valve -- internal components worn, cannot maintain gas flow to the pilot circuit
What You'll Need
How to Fix It
- Relight and Observe the Pilot Flame
Follow the instructions on the heater label. Turn gas control to PILOT, press and hold, ignite with the piezo button or a long lighter. Hold for 60 seconds. Release the knob. Watch the flame: it should be a steady blue cone about 1/2 inch tall with a small yellow tip. Weak, yellow, or wavering? The pilot orifice may be dirty. Flame is good but goes out within 30 seconds of releasing the knob? Thermocouple problem.
- Check and Replace the Thermocouple
The thermocouple is a thin copper tube running from the pilot assembly to the gas control valve. The tip sits in the pilot flame. Check that the tip is fully engulfed by the flame -- not next to it, not above it. Bent away? Gently bend it back into the flame. Still goes out? Replace it. Unscrew the connection at the gas valve with a 7/16-inch wrench. Pull the old thermocouple out of the pilot assembly bracket. Push the new one in, tighten at the gas valve. Finger-tight plus 1/4 turn with the wrench.
- Clean the Pilot Orifice
If the pilot flame is small or yellow after replacing the thermocouple, the pilot orifice is partially clogged. Turn off the gas. Remove the pilot tube from the burner assembly (it is a small aluminum tube next to the thermocouple). Use a thin needle or compressed air to clear the orifice at the tip. Do not use a drill bit or anything that could enlarge the hole. Reinstall, relight, and check for a proper blue flame.
- Check for Drafts
Pilot goes out intermittently (every few days, not immediately)? A draft may be blowing it out. Check: is the water heater near a window, dryer vent, HVAC return, or exterior door? Light a candle near the heater and watch for flicker. The draft hood on top of the heater should pull air upward -- hold a match near it to verify. If air is blowing downward through the draft hood, the vent pipe may be disconnected or blocked.
When to Call a Pro
Call a plumber or HVAC technician if the pilot still goes out after replacing the thermocouple and cleaning the orifice (gas valve may need replacement -- $150-$300), if you smell gas when the pilot is out (gas leak needs professional diagnosis), or if you see soot or carbon monoxide detector alarms near the heater (combustion problem requiring professional inspection).
Prevention Tips
- Replace the thermocouple proactively every 5-7 years. They are a wear item, like brake pads. A $5 part prevents no-hot-water emergencies.
- Keep the area around the water heater clear of dust and debris. Dust in the combustion air intake dirties the pilot orifice faster.
- Ensure the draft hood and vent pipe are properly connected and pulling air upward. A disconnected vent is both a pilot issue and a carbon monoxide hazard.
- If the pilot goes out during windy weather only, install a wind-resistant vent cap on the roof.
Frequently Asked Questions
What are the signs of a water heater pilot light keeps going out?
No hot water -- pilot light is out when you check Pilot relights but goes out within seconds of releasing the control knob Pilot relights and stays on for hours or days, then goes out again Pilot flame is small, yellow, or flickering instead of a steady blue cone Gas control knob will not stay depressed in the PILOT position
What causes a water heater pilot light keeps going out?
Failed thermocouple -- the safety sensor in the pilot flame has worn out and no longer signals the gas valve to stay open Thermocouple not positioned correctly in the pilot flame -- tip is beside the flame instead of in it Dirty or clogged pilot orifice -- produces a weak flame that does not heat the thermocouple sufficiently Draft from nearby vents, windows, or HVAC registers blows the pilot out intermittently Failing gas valve -- internal components worn, cannot maintain gas flow to the pilot circuit
When should I call a plumber for a water heater pilot light keeps going out?
Call a plumber or HVAC technician if the pilot still goes out after replacing the thermocouple and cleaning the orifice (gas valve may need replacement -- $150-$300), if you smell gas when the pilot is out (gas leak needs professional diagnosis), or if you see soot or carbon monoxide detector alarms near the heater (combustion problem requiring professional inspection).
How do I prevent a water heater pilot light keeps going out?
Replace the thermocouple proactively every 5-7 years. They are a wear item, like brake pads. A $5 part prevents no-hot-water emergencies. Keep the area around the water heater clear of dust and debris. Dust in the combustion air intake dirties the pilot orifice faster. Ensure the draft hood and vent pipe are properly connected and pulling air upward. A disconnected vent is both a pilot issue and a carbon monoxide hazard. If the pilot goes out during windy weather only, install a wind-resistant vent cap on the roof.
When should I call a plumber for water heater pilot light keeps going out?
Call a plumber or HVAC technician if the pilot still goes out after replacing the thermocouple and cleaning the orifice (gas valve may need replacement -- $150-$300), if you smell gas when the pilot is out (gas leak needs professional diagnosis), or if you see soot or carbon monoxide detector alarms near the heater (combustion problem requiring professional inspection).
Can I fix water heater pilot light keeps going out myself?
This problem is rated "DIY or pro". Most homeowners can handle this with basic tools and patience.
How serious is water heater pilot light keeps going out?
This is a medium-severity issue. Fix it soon to prevent it from getting worse.
How much does it cost to fix water heater pilot light keeps going out?
The estimated repair cost is $5 - $15 DIY (thermocouple); $150 - $300 for gas valve replacement. Costs vary by location, severity, and whether you hire a professional.
How can I prevent water heater pilot light keeps going out?
Key prevention tips: Replace the thermocouple proactively every 5-7 years. They are a wear item, like brake pads. A $5 part prevents no-hot-water emergencies.. Keep the area around the water heater clear of dust and debris. Dust in the combustion air intake dirties the pilot orifice faster.. Ensure the draft hood and vent pipe are properly connected and pulling air upward. A disconnected vent is both a pilot issue and a carbon monoxide hazard..