🔍
Navien Water Heater ⛔ Do Not Use

Navien Water Heater Error Code E109

Navien Water Heater error code E109: Exhaust blockage / restricted flue.

Last reviewed: Last updated:

Methodology: We combine OEM HVAC documentation with field repair patterns, then review for safety-first troubleshooting.

Sources: HVAC manufacturer documentation, installation/service manuals, and technician-reported repair patterns.

Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.

Is it safe?
⛔ No — stop using
Do NOT operate — potential gas or CO hazard. Ventilate the area and call a technician immediately.
Can I fix it?
Technician Required
Repair cost
Pro: $150–$600
⏱ 1–3 hours (pro)

What Does Error Code E109 Mean?

Navien Water Heater error code E109: Exhaust blockage / restricted flue.

Part that typically fails: Gas valve / igniter / heat exchanger

Do NOT operate — potential gas or CO hazard. Ventilate the area and call a technician immediately.

Symptoms You May Notice

What the Technician Will Do

🔧 Professional repair required. Do not attempt DIY — this repair requires specialized tools or certification.
  1. 1 Check your owner's manual for model-specific guidance on error code reset procedures
  2. 2 If the error persists after reset and basic checks, contact a qualified technician
⚡ Quick tip: Always try a full power reset first — turn the unit off at the breaker, wait 30 seconds, restore power.

Frequently Asked Questions

What does Navien Water Heater error code E109 mean? ▼
Error code E109 on a Navien tankless water heater indicates: Exhaust blockage / restricted flue. The unit has detected this condition and has limited or stopped operation to prevent further damage.
How do I fix Navien Water Heater error code E109? ▼
Start by powering the unit off for 30 seconds and restarting. If error E109 returns, the underlying cause (exhaust blockage / restricted flue) needs to be addressed. Check wiring connections and filters first before replacing components.
Is Navien error code E109 serious? ▼
It depends on the root cause. Some E109 errors resolve with a reset. Others indicate a failed component that requires professional repair. Don't continue operating with this error — it can lead to further damage.

More Navien Water Heater Error Codes

All Navien water heater codes → All Navien HVAC codes →

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