How to Light an AO Smith Water Heater Pilot — Step by Step

Modern AO Smith gas water heaters (post-2003, FVIR-compliant) have a built-in piezo igniter — no matches required. Older units have a lighting port for a long match. The procedure differs slightly.

Modern AO Smith — piezo igniter procedure

1. Turn gas control knob to OFF, wait 5 minutes
2. Turn knob to PILOT
3. Press and hold pilot button (large button, often red)
4. While holding pilot button, press igniter button (smaller red button) repeatedly every 2 seconds
5. Watch sight glass for pilot flame
6. Continue holding pilot button 30–60 seconds AFTER pilot is established
7. Release pilot button — pilot stays lit. If not, see troubleshooting.
8. Turn gas knob to ON. Main burner fires when thermostat calls for heat.

Older AO Smith — manual match procedure

1. Turn knob to OFF, wait 5 minutes
2. Turn to PILOT
3. Open burner access door, locate lighting port
4. Light long match or BBQ lighter at pilot tip inside burner chamber
5. Press and hold pilot button
6. Once pilot ignites, remove match. Hold pilot button 30–60 seconds.
7. Release pilot button, close access door, turn knob to ON

If pilot won't light at all

1. Verify gas supply — is gas valve open? Other gas appliances working?
2. Check igniter spark — press igniter button while watching pilot. No spark = igniter assembly failed (see our pilot assembly page)
3. Verify pilot orifice isn't blocked — debris stops gas flow. Clear with compressed air.

If pilot lights but goes out when you release the button

Thermocouple failure in ~80% of cases. Replacement is a $25–$40 part and 30-minute DIY. See our thermocouple replacement page.

If pilot lights but flame is weak/yellow

Pilot orifice has debris. Use compressed air to blow back through pilot tube. Clean the orifice mechanically with a thin wire if needed.

Safety reminders

• Smell gas? Don't light. Close supply, ventilate, call gas utility from outside
• Don't use lighter near burner chamber — only built-in igniter or long match
• If multiple attempts produce unburned gas, stop and ventilate before retrying

Bottom line

Modern AO Smith pilot lighting: OFF → wait 5 min → PILOT → hold pilot + press igniter → hold 30-60s → release → ON. If it won't stay lit, replace thermocouple. For broader troubleshooting see our troubleshooting hub.