Water Heater Pilot Light Issues

Pilot light issues on atmospheric gas water heaters are among the most common service calls. The diagnostic path is well-established — most issues resolve with thermocouple replacement.

How to relight a water heater pilot

1. Locate the gas valve on the front lower part of the water heater
2. Rotate gas valve dial to "Pilot" position
3. Press and hold the gas button (or pilot button) down
4. Click the igniter repeatedly (red button next to gas valve) — pilot should light
5. Keep gas button held for 60 seconds after pilot lights — heats the thermocouple enough to hold valve open
6. Release gas button — pilot should remain lit
7. Rotate gas valve dial to "On" — main burner cycles as needed

Pilot won\'t light at all

• Verify gas supply: other gas appliances working
• Check gas shutoff valve to the water heater is fully open
• Inspect igniter — eroded electrode or cracked ceramic = replace ($30-50)
• Clean pilot tube with compressed air — spider webs and debris restrict gas flow
• Test with match if igniter fails — verifies gas flow to pilot. If pilot lights with match, igniter is the problem

Pilot lights but won\'t stay lit

This is the most common pilot complaint. Cause is almost always the thermocouple — the temperature-sensing rod that signals the gas valve to stay open.

• Diagnose: hold pilot button 60 seconds → release → pilot dies in 5-10 seconds = thermocouple weak/failed
• Quick test: millivolt meter at thermocouple leads at the gas valve. Healthy: 25-30+ mV with pilot lit. Below 20 mV = replace
• Fix: universal thermocouple $15-25, 45-minute DIY. See thermocouple guide

Pilot stays lit but main burner won\'t fire

• Pilot OK but cold water continues: gas valve thermostat circuit failed
• Check thermostat dial: on "Vacation" or below 120°F?
• If thermostat at 120°F+ and water cold: gas valve replacement needed ($180-280 + labor)

Modern DSI (Direct Spark Ignition) — no pilot

Newer water heaters use DSI — no standing pilot. The unit sparks the burner directly on call for heat.

• No spark on call: igniter or control board fault
• Spark but no flame: gas supply, gas valve, or flame sensor
• Diagnose via fault codes on the LED status indicator

Bottom line

Pilot won\'t stay lit = thermocouple failed (most common). $15-25 DIY fix. Pilot won\'t light at all = gas supply or igniter. Main burner won\'t fire after pilot OK = gas valve. Modern DSI units use LED flash codes for diagnosis.