Rheem · Water heater
Code 33 Combustion air supply problem
What this code means
The unit isn't getting the combustion air it needs for safe, stable burning.
Most likely causes
- Blocked or restricted air intake
- Debris around the intake terminal
What to try first
Check the outside air intake terminal for blockage.
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 33 mean?
Combustion air supply problem. The unit isn't getting the combustion air it needs for safe, stable burning.
Can I fix Rheem code Code 33 myself?
Usually not. Check the outside air intake terminal for blockage. If the code returns after one reset, it needs a licensed technician.
What causes Rheem code Code 33?
The most common causes are: blocked or restricted air intake; debris around the intake terminal.
Other Rheem water heater codes
All Rheem water heater error codes →
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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.