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, checking these in order can restore hot water safely and fast.
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 wont 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’s 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.
Tip: If you smell gas, stop immediately and ventilate. Persistent odor = call a pro.
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.
Quick fix: Gently clean with fine steel wool; ensure the tip sits in the flame.
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.
Quick fix: Turn gas off, clear with compressed air or a pipe cleaner.
If gas still won’t reach the flame, the water heater pilot not lighting points here.
3) Igniter Failure
No spark from the igniter button means no flame.
Quick fix: Replace batteries (if applicable) or try a long lighter once.
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 a hot water heater won’t light or why a pilot light not lighting water heater persists.
Diagnostic Flow (Fast Decision Guide)
Check in This Order
Gas on, no leaks; ventilate
Relight correctly (hold per label)
Clean thermocouple and pilot tube
Check drafts/venting
Test gas pressure and valve
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 tradditional water heater repair or a cost-effective replacement plan.
Gas vs. Electric - Why This Article Focuses on Gas
Electric models don’t use a pilot. If you’re diagnosing a gas water heater not lighting, this guide applies. For electric no-heat issues, element and breaker checks are required instead.
Causes vs. Fixes
| Symptom | Likely Cause | First Action |
|---|---|---|
| Pilot won’t stay lit | Dirty thermocouple | Clean/test mV |
| No spark | Igniter failure | Replace igniter |
| Weak flame | Clogged pilot tube | Clear debris |
| Goes out with door closed | Drafts | Seal/redirect airflow |
| Repeated shutdowns | Control valve | Pro replacement |
Relighting the Pilot (Safe Method)
Turn gas to OFF; wait 5–10 minutes
Set to PILOT; hold knob
Press igniter; watch for steady blue flame
Hold 30–60 seconds; release
Turn to ON; confirm burner lights
If it fails after 2–3 tries, stop and call for tradditional 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 210-263-3005 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 prevents a stable flame; check other appliances.
Only a couple attempts. Smell gas or repeated failure = stop.
Components wear; frequent outages after 10–12 years suggest replacement.
Absolutely, drafts and venting issues commonly blow out pilots.
