Rheem · Water heater
Code 12 Flame loss (tankless)
What this code means
The unit ignited successfully but lost the flame during operation.
Most likely causes
- Dirty or degraded flame rod sensor
- Fluctuating or low gas pressure
- Debris in the burner assembly
What to try first
This typically requires opening the burner compartment to inspect the flame rod, which is best left to a licensed tech given the gas and combustion components involved.
Safety note: if this code returns after one clean reset, stop resetting it — repeated lockouts usually mean a real fault that needs a licensed technician. Never bypass a safety switch.
FAQ
What does Rheem error code Code 12 mean?
Flame loss (tankless). The unit ignited successfully but lost the flame during operation.
Can I fix Rheem code Code 12 myself?
Usually not. This typically requires opening the burner compartment to inspect the flame rod, which is best left to a licensed tech given the gas and combustion components involved. If the code returns after one reset, it needs a licensed technician.
What causes Rheem code Code 12?
The most common causes are: dirty or degraded flame rod sensor; fluctuating or low gas pressure; debris in the burner assembly.
Other Rheem water heater codes
All Rheem water heater error codes →
Other water heater brands: Ruud · Rinnai · Navien · Noritz · Takagi · A.O. Smith · Bradford White · State / American · Generic electric · Generic tankless
This information may contain errors or not apply to your exact model — always double-check it against your appliance's own manual before acting. If there's any chance of a gas, fire, electrical, carbon monoxide, or other safety hazard, stop and call a licensed professional or the appropriate agency (e.g. your gas utility) instead of relying on this page alone.