Quick Answer: Your water heater pilot won’t light most often due to a dirty thermocouple, clogged pilot tube, low gas pressure, airflow drafts, or a failing gas control valve. These symptoms can help a qualified professional identify the fault.
Gas Water Heater Basics: How the Pilot System Works
A gas water heater relies on a pilot light, a small, steady pilot flame, to ignite the burner assembly. The pilot light assembly includes the pilot tube, pilot orifice, and an igniter button (or automatic igniter/spark igniter on newer models). When lit, heat from the flame is sensed by the thermocouple (or thermopile), which sends a millivolt signal to keep the gas control valve open. If the flame goes out, the safety shutoff closes the gas valve to prevent gas leaks.
When this chain breaks, the water heater pilot won’t light and the unit won’t heat.
What to Check First (Safe, Step-by-Step)
Before deeper troubleshooting, confirm basics that frequently stop ignition:
Gas supply is on and the flex gas tube isn’t kinked.
There are no strong drafts or airflow problems near the unit.
You followed the manufacturer’s relighting steps (hold pilot per label).
The area is ventilated and free of residual gas.
Safety: If you smell gas, do not operate switches or attempt to relight the unit. Leave the area and call your gas utility or emergency services from a safe location.
Common Reasons a Water Heater Pilot Won’t Light
1) Dirty or Faulty Thermocouple
A dirty thermocouple can’t sense flame; a faulty thermocouple can’t send enough signal. Soot, corrosion, or age causes false shutdowns.
Professional service: A plumber can safely inspect, clean, and test the thermocouple.
Professional check: Multimeter testing—healthy output is typically 25–30 mV.
This is the most common cause when a water heater pilot light won’t light or won’t stay lit.
2) Clogged Pilot Tube or Orifice
Dust and debris block gas flow through the pilot tube or pilot orifice, weakening ignition.
Professional service: A plumber can safely inspect and clear the pilot tube or orifice.
If gas still won’t reach the flame, the pilot tube or orifice may be blocked.
3) Igniter Failure
No spark from the igniter button means no flame.
Safety: Follow the manufacturer’s instructions for replaceable igniter batteries. Do not bypass a failed igniter with an open flame.
If the automatic igniter/spark igniter never sparks, replace it.
4) Low Gas Pressure or Supply Issues
Low gas pressure, a partially closed gas regulator, or a blocked gas line can prevent ignition.
Check other gas appliances. If they struggle, pressure may be low.
Safety: Suspected blockage or pressure issues require a licensed plumber.
5) Drafts, Venting, or Combustion Problems
Excess airflow blows out the pilot; poor venting causes backdrafts.
Check ventilation issues, exhaust vent, flue vent, and the combustion chamber.
Risk: Improper venting can cause carbon monoxide buildup.
6) Worn Gas Control Valve
A failing gas control valve won’t feed the pilot consistently.
Symptoms include repeated outages and inconsistent heating.
Replacement is professional-only.
7) Age, Corrosion, or Sediment
An old water heater with worn-out components, corrosion, or sediment buildup can misfire repeatedly.
If failures are frequent and the unit is 10–12+ years old, replacement may be wiser than repeated fixes.
What the Symptoms Tell You (Noise, Flame, Timing)
Key Clues
Yellow, weak, or flickering pilot flame
Pilot lights briefly, then shuts off
Clicks without ignition (igniter issue)
Pilot goes out when door closes (draft)
These patterns help pinpoint why the water heater pilot won’t light or why the flame will not stay lit.
Diagnostic Flow (Fast Decision Guide)
Check in This Order
If you smell gas, leave the area and call for help
Follow only the manufacturer’s posted instructions
Have a plumber inspect the thermocouple and pilot tube
Have venting and airflow checked
Have gas pressure and controls professionally tested
If it still fails, stop DIY and call a pro, especially if water heater not turning on becomes consistent.
Gas Safety You Shouldn’t Skip
Never bypass a safety shutoff.
Stop if you smell gas—don’t relight.
Ensure venting prevents carbon monoxide buildup.
When to Call a Professional
If cleaning doesn’t help, or you suspect pressure/valve issues, contact a Local Plumber in your area. This avoids risks and repeat failures. Ongoing problems are classic Signs your water heater needs repair, especially during No hot water in winter when demand is high.
Preventing Pilot Problems Long-Term
Regular hot water heater maintenance reduces repeat outages:
Annual inspection of pilot components
Cleaning soot from sensors
Checking venting and gas connections
Older units may need traditional water heater repair or a cost-effective replacement plan.
Gas vs. Electric Water Heater No-Heat Problems
Gas water heaters use a pilot or electronic ignition system, while electric models rely on heating elements and breakers. If a gas unit will not light or stay lit, stop if you smell gas and call a qualified professional. Electric no-heat problems require separate electrical testing.
Causes vs. Fixes
| Symptom | Likely Cause | First Action |
|---|---|---|
| Pilot won’t stay lit | Dirty thermocouple | Professional test |
| No spark | Igniter failure | Professional diagnosis |
| Weak flame | Clogged pilot tube | Professional cleaning |
| Goes out with door closed | Drafts | Venting inspection |
| Repeated shutdowns | Control valve | Pro replacement |
Relighting the Pilot (Safe Method)
If you smell gas, leave the area and call for help
Read the manufacturer’s posted relighting label
Follow only the manufacturer’s listed steps
Do not bypass a failed igniter with an open flame
Stop and call a professional if the pilot will not stay lit
If the pilot does not stay lit, stop and call for traditional water heater repair.
Repair vs. Replace Decision
Factor Repair Replace Unit age <10 years 10–12+ years Failure frequency Occasional Frequent Parts cost Low High Efficiency Acceptable Poor Safety concerns None Present
Internal System Components (What Pros Check)
Technicians inspect the pilot light assembly, pilot tube, pilot orifice, thermocouple/thermopile, gas valve, gas control valve, flex gas tube, combustion chamber, exhaust vent, and flue vent, plus verify gas supply and gas regulator settings.
Get Reliable Hot Water - Fast
Stop fighting a pilot that won’t stay lit.
Pulliam Plumbing Services provides safe diagnostics, fast repairs, and honest replacement guidance.
📞 Call (210) 857-8583 today to restore hot water with confidence.
FAQs About Water Heater Pilot Won’t Light
A dirty or misaligned thermocouple usually can’t sense heat and shuts gas off.
Yes. Low gas pressure can prevent a stable flame and should be evaluated by a qualified professional.
Follow the manufacturer’s instructions once. If you smell gas or the pilot will not stay lit, stop and call for help.
Components wear; frequent outages after 10–12 years suggest replacement.
Absolutely, drafts and venting issues commonly blow out pilots.
