Takagi Water Heater Error Code 11: How to Fix It

Q: What does error code 11 mean on a Takagi tankless water heater?

Error code 11 on a Takagi tankless water heater means the unit experienced an ignition failure — it tried to light the burner but could not detect a flame. This can be caused by a gas supply issue, a dirty igniter or flame sensor, low gas pressure, or a blocked venting system.

Q: Can I fix Takagi error code 11 myself?

Yes, many common causes of error code 11 can be addressed by a handy homeowner. Checking and opening the gas valve, cleaning the igniter electrode, and clearing vent blockages are all DIY-friendly repairs. However, if the issue involves internal gas valve failure, gas pressure adjustment, or control board problems, you should call a licensed technician.

Q: Why does my Takagi keep showing error code 11 after I reset it?

If error code 11 keeps coming back after resetting, it means the root cause has not been fixed. The most common persistent causes are insufficient gas pressure, a coated or faulty flame sensor that cannot confirm ignition, a failing igniter that cannot generate a spark, or a venting obstruction preventing proper combustion air flow.

Q: How do I reset my Takagi water heater after error code 11?

To reset your Takagi after error code 11, close any open hot water taps, then press and hold the reset button on the unit for 3–5 seconds, or turn the power off, wait 30 seconds, and turn it back on. Then open a hot water tap to trigger a heating cycle and see if the unit ignites successfully.

Q: How much does it cost to repair a Takagi error code 11?

If the fix is a simple cleaning of the igniter or flame sensor, the cost may be minimal or zero if you do it yourself. If a technician visit is required, expect to pay $100–$200 for a service call. Replacing an igniter or flame sensor typically costs $50–$150 in parts plus labor. A full gas valve replacement can range from $200–$500 including parts and labor, depending on your location and technician rates.

Abstract

Takagi error code 11 indicates an ignition failure — the unit attempted to light the burner but could not establish a flame. This is a high-severity error that means your tankless water heater will not produce hot water until the underlying cause is resolved. Common culprits include gas supply issues, a faulty igniter, a dirty or failed flame sensor, or venting problems that prevent safe combustion.