By John Fix | Home Appliances

Why Your Water Heater Pilot Light Won’t Stay Lit (and How to Relight It in 15 Minutes)

Cold shower at 6 AM. The tank’s stone cold, the pilot light is out, and you’ve got a full house waiting on hot water. If your water heater pilot light is not working — either it won’t light at all or the pilot light keeps going out the moment you let go of the button — you’re almost certainly looking at a thermocouple problem. That’s a $15 part and a 15-minute fix. This guide walks you through diagnosis, cleaning, and replacement so you can get the hot water back on before breakfast.

Fixed this on a callout last Thursday — turned out to be the thermocouple, not a gas supply issue like the homeowner feared. The pilot would light fine, glow orange for a few seconds, then drop out the moment they released the reset button. Classic thermocouple failure. The old one had a thin layer of oxidation on the tip that was blocking the millivolt signal to the gas valve. Swapped it for a universal replacement from Home Depot, torqued the nut to finger-tight plus a quarter turn, and it’s been holding steady ever since. Nine times out of ten, that’s your culprit.

Tools & Parts You’ll Need

• Universal thermocouple (e.g., Honeywell CQ100A1013 or Home Depot part #776069 — fits most gas water heaters) — search Home Depot or Lowe’s thermocouple search
• Adjustable wrench or 7/16” open-end wrench — for the thermocouple nut at the gas valve
• Needle-nose pliers — for repositioning the thermocouple tip inside the pilot bracket
• Wire brush or fine-grit sandpaper (220 grit) — to clean oxidation off the thermocouple tip
• Compressed air can — to clear a clogged pilot orifice without disassembly
• Multimeter with mV setting (optional but recommended) — for testing thermocouple output before buying a replacement; any basic digital multimeter works
• Replacement pilot assembly (if the orifice is cracked or corroded beyond cleaning) — match to your water heater model number on the label near the bottom of the tank

See also: Why Your Dryer Takes Forever to Dry Clothes, Why Your Washing Machine Won’t Drain, and Why Is My Refrigerator Leaking Water?.

Step-by-Step: How to Relight (or Fix) Your Water Heater Pilot Light

1. Safety first — purge the gas. Turn the gas control knob (on the front of the unit) to the OFF position. Wait a full 5 minutes. This lets any accumulated gas dissipate from the combustion chamber before you introduce any ignition source. Do not skip this step. ⚠️ Safety: Never use an open flame to check for gas leaks. Mix dish soap with water in a spray bottle and apply it to connections — bubbles mean a leak. Call your gas company if you suspect a leak before doing anything else.
2. Locate the pilot assembly. Remove the outer access panel at the base of the water heater (usually just a snap-fit cover). Inside, you’ll see the burner assembly, the pilot tube (a small copper or steel line), and the thermocouple — a thin copper rod about the diameter of a pencil, positioned so its tip sits directly in the pilot flame.
3. Attempt a standard relight. Turn the gas control knob to PILOT. Press and hold the red reset button (or press down on the knob itself on older units). While holding, press the piezo igniter button — you’ll hear a click and should see the pilot flame ignite. Keep holding the button for a full 30 seconds to let the thermocouple heat up.
4. Test whether it holds. After 30 seconds, slowly release the reset button. Watch the pilot flame. If it stays lit, turn the gas control knob to your desired temperature setting (typically 120°F / “Hot”). Water heater pilot not working resolved — you’re done. If it drops out immediately, move to step 5.
5. Check thermocouple alignment and connection. The thermocouple tip must sit directly in the hottest part of the pilot flame — usually about ½ inch into the flame, not at the outer edge. Use needle-nose pliers to gently bend the thermocouple bracket so the tip is properly centered. Also check the connection nut where the thermocouple wire screws into the gas valve — it should be snug. A loose connection is a common reason the water heater pilot won’t stay lit after relighting.
6. Clean the pilot orifice. Turn the gas off at the main shutoff valve behind the water heater. Using the compressed air can, direct short blasts into the pilot orifice opening. A partially blocked orifice produces a weak, yellow flame that doesn’t generate enough heat to trigger the thermocouple properly. A healthy pilot flame is blue with just a small yellow tip. If cleaning doesn’t change the flame color, the pilot assembly may need replacement.
7. Test the thermocouple with a multimeter. Set your multimeter to the millivolt (mV) DC setting. Disconnect the thermocouple wire from the gas valve (counter-clockwise by hand). Touch the probes to the thermocouple’s end connector and body. Relight the pilot manually and hold the thermocouple tip in a lighter flame for 30 seconds. A reading of 18–25 mV means the thermocouple is functioning correctly. Under 10 mV means the thermocouple is failing and needs replacement — this is the most reliable way to diagnose why your water heater pilot light keeps going out.
8. Replace the thermocouple. With gas off and the pilot cool, use the 7/16” open-end wrench to unscrew the thermocouple nut from the gas valve (counter-clockwise). Pull the thermocouple tip free from the pilot bracket. Take the old thermocouple with you to the hardware store to match the length — they run from 18” to 36”. Install the new unit by reversing the steps: seat the tip in the pilot bracket first, route the wire, then hand-thread the nut into the gas valve and snug it with the wrench (finger-tight plus a quarter turn maximum — overtightening cracks the fitting). Relight per steps 1–4. This is the fix that resolves the vast majority of gas water heater troubleshooting calls.
9. Restore and monitor. Turn the main gas valve back on, set the temperature dial, and wait 30–45 minutes for the tank to fully reheat. Check the pilot flame once more through the inspection window to confirm it’s burning steady and blue.

What to Check If It Still Won’t Stay Lit

You’ve replaced the thermocouple, cleaned the orifice, and the water heater pilot light is still not working. Here’s where to look next:

• Draft or air current. A strong air current near the water heater can blow out the pilot flame faster than the thermocouple can register heat. Check if the access panel is missing, if a nearby HVAC vent is blowing directly at the unit, or if a window was recently opened nearby. Replace the access panel and shield the base from drafts.
• Gas supply valve partially closed. The ball valve on the gas supply line should be fully parallel to the pipe, not at an angle. A half-open valve starves the pilot of pressure. Turn it fully open and try again.
• Faulty gas control valve (thermostat/valve assembly). If the thermocouple tests good (18+ mV) but the pilot still won’t hold, the gas control valve itself may be failing. This is not a DIY repair. The gas valve typically costs $80–$150 plus labor. On a newer unit it’s worth replacing; on an older unit, factor that against a full replacement.
• Sediment-related combustion issues. Years of mineral buildup at the bottom of the tank can cause rumbling, popping, and inconsistent combustion that disrupts the pilot. Flush the tank via the drain valve to clear sediment.

When to Call a Pro

Some water heater issues are firmly in professional territory. Call a licensed plumber or gas technician if:

• The gas control valve needs replacement. Working on the gas valve itself involves disconnecting gas fittings and requires a licensed tech in most jurisdictions.
• You smell gas and can’t locate the source. Evacuate the house, leave the door open, and call your gas utility from outside.
• Your carbon monoxide detector has triggered. CO is odorless and deadly. Get everyone out, call 911, and do not re-enter until emergency services clear the space.
• The water heater is more than 15 years old. The average lifespan is 8–12 years. Spending money on a gas valve repair on a 15-year-old unit is rarely the smarter investment.
• You see corrosion, rust-colored water, or visible cracks on the tank body. These are signs of internal tank failure.

Frequently Asked Questions

Q: How long should I hold the pilot button before releasing?
A: Hold the button for a minimum of 30 seconds after the pilot ignites. The thermocouple tip needs to reach operating temperature — roughly 400°F — before it generates enough millivoltage to hold the gas valve open. On older units, try holding for 45–60 seconds. If it still drops out, the thermocouple is the problem.

Q: My pilot lights but the water is still cold — why?
A: If the pilot is lit but the main burner isn’t firing, check that the temperature dial is set above the current water temperature. If the dial is correct and the main burner never comes on, the gas control valve or thermostat assembly is likely faulty.

Q: How often does a thermocouple need replacing?
A: In normal use, a thermocouple lasts 5–10 years. If yours is failing at 3–4 years, check for draft issues or a slightly misaligned pilot flame that’s overheating the tip.

Q: Is it safe to relight the pilot myself?
A: Yes, for a standard relight or thermocouple replacement, a careful homeowner can handle this. The key rules: wait 5 minutes after turning off the gas before introducing any ignition, never force a gas fitting, and test for leaks with soapy water after any connection work.

Sources

• Rheem Water Heater Owner Manuals and Troubleshooting Guides — rheem.com/product_manuals/
• Family Handyman, “How to Relight a Water Heater Pilot Light” — familyhandyman.com
• U.S. Consumer Product Safety Commission, Water Heater Safety Resources — cpsc.gov

Our Point of View

The thermocouple is one of the most underrated maintenance items in a home. It costs $12–$18, takes 15 minutes to replace, and it’s the reason 80% of “my water heater stopped working” calls don’t actually require a service visit. Stock one in your parts drawer — the Honeywell CQ100A1013 fits the majority of residential gas water heaters made in the last 20 years. If you’ve been calling a plumber every time the pilot goes out, you’ve been paying $100+ for a $15 fix.

That said, know your limits. The thermocouple and pilot assembly are fair game for a handy homeowner. The gas control valve is not. I’ve seen DIYers crack a valve fitting trying to muscle it loose, turning a $15 repair into a $300 emergency call. The rule I follow: if it unscrews with a 7/16” wrench and doesn’t involve the main gas line, you can do it yourself. If you need a pipe wrench or you’re disconnecting a gas union, call a licensed plumber.

One more thing worth knowing: if you’re diagnosing why your water heater pilot light keeps going out and you have an older Honeywell or White-Rodgers gas valve, there are known batch failures on valves manufactured between 2010–2015. If the thermocouple tests good and the pilot still won’t hold, check the model number on your gas valve against current recall and service bulletin lists before spending money on more parts.

This article was reviewed by our editorial desk for accuracy. John Fix is verified at LinkedIn. Sources are linked inline and listed below. We update articles when new information becomes available. Last reviewed: June 2, 2026.

John Fix

John Fix is a master handyman with over 20 years of experience in home repairs and small-engine maintenance. He believes every problem has a logical solution if you have the right tools and patience.

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