Rheem water heater error 12

What causes 12

The flame went out during operation.

What to do

Check the gas supply and vent. If it repeats, the flame rod needs cleaning.

Can I fix it myself?

No. This is a fault a technician should handle; keep using the appliance and it can get worse or become unsafe.

If the code comes back

Book a visit and add the code to the booking. A technician arrives knowing which parts to bring, diagnoses the water heater for a flat $89 and gives you an exact quote before doing any work.