A water heater pilot light that won’t stay lit usually means a weak thermocouple, a dirty pilot, drafts, or a bad gas valve—start with safe steps.
Nothing stalls a day like a shower that runs cold. If the pilot on your gas water heater keeps quitting, the root is usually simple. A sensor isn’t seeing flame, the pilot flame is weak or mis-aimed, air is blowing the flame out, or the gas valve isn’t cooperating. This guide gives clear checks, safe fixes, and when to call a pro.
Fast Symptom-To-Fix Guide
Scan this table, then jump to the section that matches what you see. Work with the gas knob at OFF when not actively lighting, and follow the relight label on your tank.
| Symptom | Likely Cause | What To Try First |
|---|---|---|
| Pilot lights, dies when you release the button | Weak thermocouple/thermopile or loose connection | Snug the connection, clean tip, then replace if weak |
| Pilot won’t light at all | No gas to pilot or clogged orifice | Confirm gas on; clean pilot tube/orifice |
| Pilot flickers, noisy, or lifts off | Drafts or backdraft from vent | Close doors, check vent cap, fix downdraft |
| Yellow, sooty pilot flame | Dirty pilot or low air | Clean pilot inlet; clear dust and lint |
| Burner fires, then shuts down | Flame sensor weak, spill switch trip, or gas valve fault | Reset spill switch; test sensor; call a pro for valve |
| Goes out overnight | Intermittent draft or gas pressure swing | Shield from drafts; ask utility to check pressure |
Pilot Light Won’t Stay Lit On Hot Water Heater — Causes And Fixes
Dirty Or Mis-Aimed Pilot Flame
The pilot orifice is tiny. Dust and rust flake clog it and starve the flame. A weak flame won’t heat the sensor, so the gas valve closes the pilot circuit the moment you release the button.
Turn the gas control to OFF and wait five minutes. Remove the pilot tube from the burner bracket. Blow out the orifice with canned air; do not ream it with a pin. Reinstall, then align the flame so it touches the top third of the sensor tip.
Weak Thermocouple Or Thermopile
On standing-pilot tanks you’ll see a skinny copper probe beside the pilot. That probe makes a tiny voltage when heated. If the tip is oxidized, bent out of the flame, or the lead is loose at the gas valve, the pilot drops as soon as you let go of the button.
Shut gas, let the chamber cool, then polish the probe gently with fine steel wool. Straighten the bracket so the flame wraps the tip. Hand-snug the compression nut at the gas valve. If the pilot still quits, install the correct replacement for your model.
Gas Control Valve Trouble
When the sensor is healthy and the flame is blue and steady, the pilot still fading points to an aging gas control valve. Internal safety circuits or a sticky magnet can release the pilot path. This is not a DIY repair on sealed units or models under warranty.
Document the model and serial, take clear photos, and price the part against a replacement tank. If the tank is near end of life, a new heater can make better sense.
Drafts, Backdraft, And Poor Combustion Air
Wind, attic pull, or a running exhaust fan can pull the flame off the sensor. Water heaters in tight closets or hot garages can also struggle to breathe.
Close nearby doors, stop box fans, and check the vent for loose joints. Shine a mirror by the draft hood with the burner on; fogging or heat curling down is a red flag for backdraft. Add make-up air or fix the vent run before chasing parts.
Spill Switch Or FVIR Trip
Many newer tanks have a spill or rollout switch that opens if hot flue gases spill from the draft hood. FVIR (flammable vapor ignition resistant) chambers also trip when vapors are detected. Both conditions kill the pilot until the cause is cleared.
Look for a small reset on the spill switch near the draft hood. If it trips again, stop and fix the vent or air cause. For FVIR resets and screens, follow the label for your exact model.
Moisture And Condensation
Cold make-up water hitting a cool tank can drip from the flue baffle. Drips that land on the pilot can sizzle it out. This shows up right after long draws or first thing in the morning.
Let the tank warm fully, then relight. Verify the flue baffle is seated and the pilot bracket hasn’t shifted under it.
Five-Minute Quick Checks
- Turn the control to OFF and wait five minutes so gas can clear. Then follow the lighting label exactly.
- Watch the pilot flame. It should be steady, mostly blue, and aimed at the sensor tip.
- Lightly tug the thermocouple lead at the gas valve. Hand-snug if loose.
- Wave a piece of cardboard near the draft hood. If the flame wavers or pulls, fix drafts before parts.
- Peek through the sight glass for soot. Heavy soot means a cleaning and air check are due.
For model-specific pilot relight steps, see your tank’s label or the maker’s guide. Many brands keep a clear walk-through online with photos and safety notes.
Safe Relight And Wait Times
When a pilot goes out, patience helps. Gas needs a short window to disperse before you try again. Many utilities advise waiting about five minutes with the control at OFF, then following the printed steps.
If you ever smell gas strongly, do not relight. Leave the area at once and call your gas utility from outside. For basics on shutoffs and safety, review your utility’s gas safety guidance.
How To Test A Thermocouple
You can do a quick field check without special gear. Light the pilot and hold the button. After a full minute of heating, release. If the pilot dies right away and the flame was strong on the tip, the sensor is likely weak.
With a meter, test output in millivolts on a standing-pilot thermocouple. A healthy probe often shows a few dozen millivolts under flame. Low output even with a bright blue flame means replace the probe.
Cleaning The Pilot Assembly
What You Need
- Flashlight and long lighter
- Canned air and a soft brush
- Small wrench for the pilot tube nut
- Fine steel wool for the sensor tip
Steps
- Turn gas to OFF and let the chamber cool.
- Remove the burner access cover. Note the routing of the pilot tube and sensor lead.
- Crack the pilot nut loose and ease the tube from the bracket.
- Blow out the orifice and tube. Brush lint from air inlets.
- Reinstall, align the flame to wrap the sensor tip, then relight per the label.
When The Pilot Still Drops
At this point a weak sensor or a tired gas control is most likely. Replace the sensor first; it’s simple and cheap. If that fails, pricing a valve against a new tank is smart, especially near the 10-year mark.
Also look upstream. Intermittent gas pressure or a failing regulator can starve a pilot. A quick call to the utility can rule that out.
Parts, Costs, And DIY Level
| Part Or Fix | Typical Cost | DIY Level |
|---|---|---|
| Thermocouple or thermopile | Low to moderate | Basic hand tools |
| Pilot assembly (with orifice) | Low to moderate | Intermediate |
| Gas control valve | High | Pro recommended |
| Vent repair or wind cap | Varies | Intermediate to pro |
| Make-up air grille | Low | Intermediate |
| Utility gas-pressure check | Often free | Call utility |
Placement And Venting Checks
Measure clearances around the heater. Boxes, paint cans, or tight doors choke air and make the flame lazy. Clear the area. If your tank lives in a garage or attic, heat swings and wind can set up downdrafts that swipe the pilot.
Stand back and watch the draft hood while the burner runs. The plume should rise. Any pull of warm air down the hood points to vent slope, length, or cap issues that need correction.
Prevent The Next Outage
- Vacuum lint and dust near the base every few months.
- Keep doors and louvers open enough to feed air.
- Shield from wind with a proper vent cap, not tape or makeshift covers.
- Replace the pilot assembly when cleaning no longer restores a crisp flame.
- Schedule a pro check if spill switches trip or you see soot returning.
When To Stop And Call
Stop DIY work if you smell gas, see scorched wiring, or the pilot chamber is damaged. Stop if the tank leaks, if the draft test fails, or if the pilot drops even with a new sensor and clean flame. A licensed tech can test the gas valve magnet, check manifold pressure, and verify vent sizing.
Model-Specific Notes
Manufacturers publish lighting steps, parts lists, and diagrams for each line. Grab the model and serial from the data plate and pull the guide. It will show the exact pilot setup, sensor type, and any reset locations.