When a gas water heater’s pilot won’t light, check gas supply, airflow, ignition parts, and the thermocouple or thermopile before calling a pro.
You came here because the flame won’t start and the water’s cold. This guide gives fast checks first, then deeper steps that solve most ignition problems at home. You’ll also see clear safety notes and links to the official instructions many brands print on the tank label.
Fast Safety Checks Before You Try Anything
If you smell gas, don’t try to light the appliance, don’t flip switches, and step outside to call your gas supplier or local fire service. If there’s no gas odor, move on to the quick checks below. Keep the area clear of lint and solvents. Good airflow matters for a clean, steady flame.
Quick Triage: What The Symptoms Point To
Use this table as a fast map from symptom to likely cause and a first step. It’s broad by design so you can spot patterns quickly.
| Symptom | What It Suggests | First Step |
|---|---|---|
| Igniter clicks but no flame appears | Closed gas valve, air in line, clogged pilot orifice | Confirm both gas shutoffs are in line with the pipe; wait a full minute between lighting tries |
| Pilot lights but goes out when you release the button | Weak or misaligned thermocouple/thermopile; dirty pilot flame | Re-seat the sensor tip in the flame path; clean soot from the pilot assembly |
| No clicking from igniter | Cracked piezo lead, loose connector, failed spark module | Inspect the wire and connectors; reseat firmly; replace if cracked |
| Status light shows error flashes | Control sees a fault (overheat, sensor trip, low millivolts) | Match flashes to the label chart; follow the specific reset or part check |
| Flame starts, then sputters out | Starved airflow at the intake screen; dust on flame arrestor | Vacuum the base air screen and clean the arrestor with a soft brush |
| Draft blows the flame out | Backdraft from vent, open doors, or fans | Close nearby doors, stop strong fans, check vent rise and clearances |
How Pilot Lighting Works In Simple Terms
The pilot flame heats a small sensor (thermocouple or thermopile). That heat makes a tiny electrical signal the gas control expects to see. No signal, no gas. That’s why a weak, yellow flame or a sensor sitting outside the flame path will shut things down even when gas is available.
When A Gas Heater Pilot Won’t Ignite: Quick Wins
1) Confirm Gas Supply And Valve Positions
There are usually two shutoffs: a house side valve and the little knob on the control. Both must be open. The handle should be parallel to the pipe. If your unit was just installed or recently off, air may be in the line. Hold the pilot button as directed by the label and give the gas a moment to reach the burner before each spark attempt.
2) Follow The Exact Lighting Steps On The Tank Label
Every tank prints step-by-step lighting instructions near the viewing window. The order matters: set control to OFF, wait the stated time to clear any gas, press and hold the pilot button, spark, then keep holding as the sensor heats. For a clear walkthrough, see the manufacturer’s guide here: pilot lighting instructions.
3) Clean The Pilot Orifice And Flame Path
Dust and lint narrow the tiny pilot opening. With gas off and the area cool, remove the burner assembly as your label or manual shows. Blow out the pilot orifice with compressed air, or use a soft brush. Reinstall, making sure the pilot tube is seated and the flame will strike the sensor tip directly.
4) Reseat Or Replace The Thermocouple Or Thermopile
The sensor tip should sit in the blue cone of the pilot flame. If the flame looks weak or yellow, clean the pilot first. If the flame is strong but the pilot dies when you release the button, the sensor may be failing. Many assemblies come as a single replacement kit (pilot, sensor, and spark lead). Match your model and part number.
5) Restore Airflow At The Base
Most modern tanks use a flame arrestor and intake screen at the base. They load up with lint in laundry rooms and closets. Pull the lower cover, vacuum the screen all the way around, and brush the arrestor plate gently. Refit the door and grommets so the chamber seals correctly, then try lighting again.
6) Read The Status Light And Act On The Code
If your control has an LED, it will blink a pattern with a short pause. One blink every few seconds means normal standby with a lit pilot. Multiple blinks map to clear steps on the label. Typical hits include low sensor voltage, limit trip, or sensor failure. Match the code to the label chart and follow the listed action.
Step-By-Step: A Clean Lighting Attempt
Prep The Area
Remove clutter, solvents, and cardboard around the heater. Open the room door to improve makeup air. If the tank sits on a platform, clear the underside too.
Set Controls
Turn the control to OFF and wait the full time stated on the label. This clears unburned gas. While you wait, confirm the house gas valve is open and the flex connector isn’t kinked.
Ignite The Pilot
Turn the control to PILOT, press and hold the pilot button, and press the igniter until you see a steady blue flame at the viewport. Keep holding the pilot button for the hold-time on the label so the sensor heats fully. Release slowly. If the flame drops, repeat once more after a short pause.
If It Still Won’t Stay Lit
- Re-aim the sensor so the tip sits deeper in the blue cone.
- Clean the pilot orifice again; a speck can block flow.
- Check the igniter wire for cracks and the push-on connector for a snug fit.
- Replace the combined pilot/sensor/igniter assembly if the flame is strong but the pilot drops each time.
Vent And Draft Checks
A sharp downgrade in draft will snuff a small flame. Look for a minimum rise in the vent before the first elbow and secure joints. Keep nearby exhaust fans and open doors from pulling air across the flame. If you see backdraft signs (warm air spilling at the draft hood), stop and call a licensed tech.
Common Fault Codes In Plain Language
Many gas controls flash patterns for low sensor voltage, over-temperature trip, sensor fault, or general lockout. Here’s a simple map you can copy next to the tank. Always confirm the exact chart on your label.
| Blink Pattern | Meaning | Action You Can Take |
|---|---|---|
| No flash | Pilot not lit / no power | Relight per label; check connectors; clean pilot |
| 1 flash | Normal standby | Burner fires on call for heat |
| 2 flashes | Low sensor millivolts | Clean flame path; reseat or replace sensor |
| 4 flashes | Limit/over-temp trip | Let unit cool; check sediment and airflow; reset if allowed |
| 5 flashes | Sensor failure | Replace pilot/sensor assembly or gas control as directed |
| 7 flashes | Lockout (often vapor sensor) | Clear fumes, fix cause, follow manual reset steps or call a tech |
Fixes That Solve Most Cases
Clean Or Replace The Pilot Assembly
Grime in the orifice makes a lazy flame that won’t heat the sensor. A new assembly restores stable ignition in one shot. Match the exact kit for your model so the bracket and tubing lengths land correctly.
Swap A Tired Thermocouple Or Thermopile
If the pilot lights and drops every time, the sensor is a prime suspect. A fresh part costs little and often comes bundled with the pilot tube and spark lead. Tighten compression fittings snugly and check for leaks with soapy water.
Repair Loose Or Damaged Igniter Leads
That faint click with no spark usually traces to a cracked wire or a loose push-on terminal. Route the new lead away from sharp edges and hot surfaces.
Clear The Intake Screen And Flame Arrestor
Lint around the base chokes the chamber. A quick vacuum and brush restore airflow. Refit the inner door, nuts, and grommets so the chamber seals tight again.
When A Lockout Stops Lighting
Some controls enter a lockout if they sense flammable vapors or repeated failed lights. First, remove any fume sources (paint, cleaners, gasoline), air out the room, and let the unit sit. Then follow the label’s reset steps. If the code returns, the sensor or control may need replacement. Don’t bypass safety devices.
Smart Safety Reminders
- If you smell gas: leave the area and call the gas supplier from outside. Don’t strike matches or flip switches.
- Keep a carbon monoxide alarm near sleeping areas. Poor draft or partial combustion can raise CO inside a home. Read the basics here: CO safety guidance.
- Water hotter than 125°F can scald fast. If you raised the setpoint during testing, turn it back down when you’re done.
Parts And When To Call A Pro
Ignition parts are common wear items. If the tank is within warranty, check coverage before you buy anything. Call a licensed tech if you see scorched wiring, repeated lockouts after a clean reset, backdraft at the draft hood, or a gas smell at any fitting. For lighting steps and warnings printed by a major brand, see the use & care manual section labeled “What To Do If You Smell Gas.”
Simple Maintenance To Prevent The Next No-Light
- Vacuum the intake screen every few months in laundry rooms and dusty spaces.
- Keep solvents and fuels far from the heater; fumes can trip sensors.
- Flush sediment yearly so the burner doesn’t overheat the base and trip limits.
- Check the vent rise and secure joints so draft stays steady on windy days.
- Snap a phone photo of your status-light chart and model number for quick reference later.
Quick Checklist You Can Tape To The Tank
Before Lighting
- Clear the area; open the room door for fresh air.
- Turn control to OFF and wait the full label time.
- Confirm both gas valves are open.
Lighting Steps
- Set control to PILOT.
- Press and hold the pilot button, spark until a steady blue flame shows, hold for the full warm-up time, release slowly.
If It Fails
- Clean pilot orifice; re-aim sensor in the flame.
- Check igniter lead and connections.
- Replace pilot/sensor assembly if the flame is strong but won’t hold.
- Read status flashes and act on the chart.
Wrap-Up: Get That Flame Back Safely
Most no-light cases boil down to closed gas, a dirty pilot, a tired sensor, or a starved air intake. Work through the checks above, follow the label steps exactly, and use the linked manuals when you need model-specific detail. If something feels unsafe or the code returns after a clean reset, call a licensed pro.