Error Code	Symptom	Fault Type	Guide
E0	Rheem tankless water heater displays E0 and will not run a hot water cycle	Control Panel Communication Error	View Details
E1	Rheem tankless water heater shows E1 and shuts down shortly after opening a hot water tap	Low Water Flow / Flow Sensor Fault	View Details
E11	Rheem tankless water heater shows E11 and shuts down immediately after trying to start	No Ignition / Ignition Failure	View Details
E12	Rheem tankless water heater displays E12 and shuts down after ignition	Flame Loss During Operation	View Details
E13	Rheem tankless water heater shows E13 and shuts down with hot exhaust	Exhaust Overheat / Heat Exchanger Overheat	View Details
E14	Rheem tankless water heater displays E14 and will not run	Overheat Cutoff / Safety Thermostat Trip	View Details
E15	Rheem tankless water heater shows E15 and does not start	Booster Pump / Recirculation Pump Fault (models with built-in pump)	View Details
E16	Rheem tankless water heater displays E16 and shuts down intermittently	Abnormal Combustion / Flame Signal Error	View Details
E2	Rheem tankless water heater displays E2 and burner will not ignite	Inlet Thermistor (Cold Water Temperature Sensor) Fault	View Details
E20	Rheem tankless water heater shows E20 and will not operate	Communication Error Between Main PCB and Remote Controller	View Details
E29	Rheem tankless water heater displays E29 and shuts down	Condensate Drain Blockage (Condensing Models)	View Details
E3	Rheem tankless water heater shows E3 and shuts down during operation	Outlet Thermistor (Hot Water Temperature Sensor) Fault	View Details
E30	Rheem tankless water heater shows E30 and will not start	Flame Rod Short / Ground Fault	View Details
E31	Rheem tankless water heater displays E31 and shuts down	Inlet Water Temperature Sensor Range Error	View Details
E32	Rheem tankless water heater shows E32 and will not operate	Outlet Water Temperature Sensor Range Error	View Details
E33	Rheem tankless water heater displays E33 and shuts down	Heat Exchanger Temperature Sensor Fault	View Details
E35	Rheem tankless water heater shows E35 and will not run	Abnormal Gas Valve Signal	View Details
E4	Rheem tankless water heater displays E4 and water temperature fluctuates or unit shuts off	Combustion Air / Exhaust Temperature Sensor Fault	View Details
E40	Rheem tankless water heater displays E40 and shuts down	Fan Motor Speed / Tachometer Error	View Details
E5	Rheem tankless water heater shows E5 and shuts down when trying to heat water	Overheat / High Limit Protection Trip	View Details
E50	Rheem tankless water heater shows E50 and will not operate	Internal Control Board Error	View Details
E7	Rheem tankless water heater displays E7 and will not ignite	Gas Solenoid Valve Circuit Fault	View Details
E76	Rheem tankless water heater displays E76 and will not start	Dip Switch / Configuration Error	View Details
E8	Rheem tankless water heater shows E8 and shuts down during operation	Fan Motor / Combustion Blower Fault	View Details
E9	Rheem tankless water heater displays E9 and will not operate	Ignition Failure / Flame Detection Error	View Details
E99	Rheem tankless water heater shows E99 and locks out	Lockout Due to Repeated Ignition or Safety Failures	View Details
ECO	Rheem electric or gas tank water heater shows ECO trip (Energy Cut Off) and will not heat	High Limit Thermostat Trip	View Details
Element Failure	Rheem electric water heater has power but no hot water; continuity test shows open heating element	Burned-Out Heating Element	View Details
FVS	Rheem FVIR gas tank water heater status light flashes indicating flammable vapor sensor lockout	Flammable Vapor Sensor (FVS) Lockout	View Details
–	Rheem gas water heater pilot will not light or will not stay lit	Pilot Ignition / Flame Holding Failure	View Details
–	Rheem tankless water heater delivers hot water but temperature fluctuates up and down during a shower	Inconsistent Outlet Temperature / Flow Modulation Issue	View Details
–	Rheem tankless water heater does not fire when a single low-flow faucet is opened	Minimum Activation Flow Not Reached	View Details
–	Rheem water heater burner cycles on and off rapidly, causing fluctuating water temperature	Short Cycling / Temperature Overshoot	View Details
–	Rheem water heater causes water hammer or banging noises in pipes when heating or shutting off	Hydraulic Shock / Water Hammer	View Details
–	Rheem water heater drain valve leaks when closed	Leaking Drain Valve	View Details
–	Rheem water heater emits a rotten egg or sulfur smell from hot water taps	Hydrogen Sulfide Odor in Hot Water	View Details
–	Rheem water heater has hot water for a few minutes, then quickly turns lukewarm or cold	Insufficient Hot Water Capacity / Single Element or Burner Operation	View Details
–	Rheem water heater hot water is too hot, risking scalding	Overheating / Thermostat Out of Calibration	View Details
–	Rheem water heater leaks from the temperature and pressure (T&P) relief valve discharge pipe	Excessive Temperature or Pressure / T&P Valve Discharge	View Details
–	Rheem water heater leaks water from the bottom of the tank	Tank Corrosion / Internal Tank Leak	View Details
–	Rheem water heater makes loud popping or rumbling noises during heating	Sediment Buildup / Boiling Under Sediment Layer	View Details
–	Rheem water heater produces no hot water at any faucet	Complete Loss of Heating Function	View Details
–	Rheem water heater shows condensation or water on top of the tank	Condensation or Top-Side Leak	View Details
–	Rheem water heater shows signs of rust-colored water from hot taps	Internal Corrosion / Rust Contamination	View Details
–	Rheem water heater trips the circuit breaker or blows fuses repeatedly	Electrical Short or Overcurrent	View Details

Rheem Water Heaters Error Codes

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