Rinnai Water Heater Error Code 13: How to Fix It

Q: What causes Rinnai error code 13?

Rinnai error code 13 is caused by abnormal combustion inside the unit. The most common causes are a dirty or clogged burner, blocked or restricted intake/exhaust venting, insufficient gas pressure, a fouled flame sensor that cannot detect the flame, or a failed igniter. Environmental factors like very cold air or debris near vent terminations can also trigger this error.

Q: Can I reset a Rinnai error code 13 myself?

Yes, you can reset it by pressing and holding the ON/OFF button for 2 seconds to turn the unit off, waiting 30 seconds, and then turning it back on. However, if the code 13 keeps coming back, a reset alone is not a fix — you need to address the underlying cause, such as cleaning the burner or clearing a blocked vent.

Q: How often should I clean my Rinnai tankless water heater burner?

Rinnai recommends a professional annual service inspection, which includes burner and combustion chamber cleaning. In dusty environments or homes with pets, more frequent inspections may be warranted. The air intake filter should be checked and cleaned every 3–6 months depending on how dusty your installation environment is.

Q: Is Rinnai error code 13 dangerous?

Error code 13 is rated medium severity. The unit will lock out and stop producing hot water, which is a built-in safety response to abnormal combustion. You should address it promptly. If at any point you smell gas or suspect carbon monoxide (headaches, dizziness, nausea), evacuate immediately and call emergency services — do not attempt to troubleshoot under those conditions.

Q: How much does it cost to fix Rinnai error code 13?

If the fix is a DIY burner cleaning and vent clearing, your cost is minimal — just time and perhaps a can of compressed air. If a technician is needed for burner cleaning and inspection, expect to pay $100–$250 for a service call depending on your region. If components like the flame sensor, igniter, or gas valve need replacement, costs can range from $150–$500+ including parts and labor.

Abstract

Rinnai error code 13 signals an abnormal combustion event inside your tankless water heater, meaning the burner is not igniting or burning fuel cleanly and efficiently. This is most commonly caused by a dirty or clogged burner, restricted airflow, improper gas pressure, or a venting problem that disrupts the combustion process. Left unresolved, this error will prevent your unit from producing hot water and can cause repeated lockouts.