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Takagi Error Code 121: Flame Failure
⚠️ The Takagi tankless water heater has detected a flame failure. This could indicate a gas leak or carbon monoxide risk. Shut down the unit immediately and call a qualified technician.
How to Fix Takagi Code 121
- Step 1: Ensure that the gas supply to the unit is turned on. Check the gas shut-off valve near the unit and at the gas meter.
- Step 2: Check for any obstructions around the vent termination outside the house. Clear any snow, ice, or debris.
- Step 3: Reset the unit by turning it off and then on again. If the error persists, do not continue to reset it. Call a qualified HVAC technician or plumber immediately.
What Does Takagi Error Code 121 Mean?
Error code 121 on your Takagi tankless water heater indicates that the unit attempted to ignite the burner, but the flame was not properly established or was lost during operation. This is a safety feature that shuts down the unit to prevent unburnt gas from accumulating, which could lead to a dangerous situation. The system monitors the flame through a flame rod sensor. If the sensor doesn't detect a flame when it should, or if the flame is lost mid-cycle, it triggers this error. This issue prevents the unit from providing hot water and needs immediate attention.
Common Causes of Takagi Code 121
- Gas supply interruption (e.g., gas valve closed, low gas pressure)
- Faulty flame rod sensor or wiring
- Blocked or partially blocked vent system restricting airflow
- Igniter failure preventing initial flame
- Malfunctioning gas valve not opening fully or at all
Applicable Takagi Models
Need a Pro to Fix Takagi Code 121?
This error requires immediate attention from a licensed HVAC technician. Do not attempt repair yourself.
Find a Licensed Tech Near You →Replacement Parts for Takagi HVAC System Code 121
Flame Rod Sensor
Gas Valve
Igniter