If your water heater is displaying a code, that code is actually good news. It means your unit has self-diagnosed a problem and is telling you exactly what’s wrong. The trick is knowing how to read it.
This guide covers the most common error codes for every major brand we service — Rheem, Navien, Rinnai, Bradford White, Noritz, GE, and Whirlpool — and tells you whether each one is a simple reset or a call-a-pro situation.
Jump to Your Brand
Before doing anything on any brand: Try a power cycle first. Turn the unit off at the breaker (or unplug it), wait 30 seconds, and restore power. Many temporary faults clear on their own after the underlying condition resolves.
Rheem Error Codes
Numeric codes on front panel · EcoNet app alerts on Wi-Fi models
Continuous Combustion / Imperfect Combustion Alarm
Try Reset FirstWhat it means: The unit has been running for over an hour continuously, or combustion quality is poor.
What to do: Close all hot water taps. If you have a recirculation pump, turn it off temporarily. Check the exhaust vent and air inlet filter for blockages. If the code keeps returning — call a pro.
What it means: The unit can’t get enough air for combustion, or exhaust gases aren’t venting properly. Most likely cause: blocked vent pipe, debris near the exterior vent, or a bird/rodent nest in the flue.
What to do: Check the exterior vent for visible obstructions. If clear — call a pro. Vent blockages can create carbon monoxide risks.
No Ignition / Ignition Failure
Try Reset FirstWhat it means: The unit tried to ignite but couldn’t detect a flame. Most likely causes: gas valve not fully open, air in the gas line, blocked air inlet, or low water flow.
What to do: Confirm the gas valve is open and try a power cycle. If the code returns — call a pro.
Flame Failure
Try Reset FirstWhat it means: The unit ignited but the flame went out during operation. Most likely causes: low gas pressure, dirty or faulty flame rod, or partially closed gas valve.
What to do: Check the gas valve is fully open and try a reset. If it keeps appearing — call a pro.
What it means: The unit overheated and shut down as a safety measure. Most likely cause: blocked venting, scale buildup in the heat exchanger, or set temperature too high.
What to do: Let the unit cool, check vent paths. If it overheats again — call a pro for heat exchanger inspection and possible descaling.
Flow Sensor / Clogged Inlet Filter
Try Reset FirstWhat it means: The unit isn’t detecting proper water flow and won’t fire. Most likely cause: dirty or clogged water inlet filter screen (very common), or a faulty flow sensor.
What to do: Turn off the unit. Locate and rinse the cold water inlet filter screen. Try again. If the code persists — call a pro.
What it means: The condensate neutralizer needs to be replaced. Specific to condensing Rheem models.
What to do: Call a pro.
What it means: Mineral scale has built up in the heat exchanger.
What to do: Call a pro for a professional descaling flush. Annual maintenance prevents recurrence.
Remote Control Communication Fault
Try Reset FirstWhat it means: The control board and remote panel have lost communication.
What to do: Check wiring connections and try a power cycle. If it persists — call a pro.
Rinnai Error Codes
Numeric codes on front panel · Control-R app alerts
Reset tip: Press the On/Off button, wait, and press again. For harder lockouts, unplug the unit for 30 seconds.
What it means: The unit is in freeze protection mode but cannot fire the burner.
What to do: Call a pro.
Power Interruption During Bath Fill
Try Reset FirstWhat it means: Power was interrupted while the bath fill function was active.
What to do: Turn off all hot water taps. Press the On/Off button twice. Turn the hot water back on and test. If it doesn’t clear — call a pro.
What it means: Blocked intake or exhaust venting. Most likely cause: debris, nest, or obstruction at the exterior vent. Also check that venting materials are Rinnai-approved.
What to do: Inspect the exterior vent for visible obstructions. If clear — call a pro.
What it means: Combustion is irregular. Most likely cause: blockage or scale buildup on the burner; debris in the combustion chamber.
What to do: Call a pro for a burner inspection and cleaning.
No Ignition
Try Reset FirstWhat it means: The unit attempted ignition but could not establish a flame. Most likely causes: no gas supply or low gas pressure, air in the gas line, blocked air intake, grounding issue.
What to do: Verify the gas valve is fully open and other gas appliances work. Try a 30-second power reset. If still showing — call a pro.
Flame Failure
Try Reset FirstWhat it means: The unit ignited but lost its flame during operation. Most likely causes: low gas pressure, dirty flame rod or spark igniter, loose wiring harness, blocked vent.
What to do: Try a power reset. If it recurs — call a pro.
What it means: The thermal fuse has tripped due to overheating. Most likely causes: scale buildup restricting water flow, blocked vent, short-cycling from low water flow.
What to do: Call a pro. The thermal fuse may need replacement and the heat exchanger likely needs descaling.
What it means: Water temperature exceeded the safety limit. Most likely cause: scale buildup, blocked vent, or faulty temperature sensor.
What to do: Call a pro. Do not continue operating the unit.
What it means: Mineral scale has accumulated in the heat exchanger. This is the only Rinnai code that allows the unit to keep running — the display alternates between “LC” and the temperature setting.
What to do: Do not ignore this code even though the unit still works. Schedule a professional heat exchanger flush. Repeated LC codes will eventually lock out the unit permanently. Call a pro.
Service Reminder
Schedule ServiceWhat it means: The unit has reached a set number of operational hours and is due for professional service. This is not an error — it’s a maintenance reminder.
What to do: Press the On/Off button 5 times within 5 seconds to temporarily reset it, then schedule a service call.
What it means: The main control board (PCB) has encountered a critical fault.
What to do: Try unplugging for at least one minute. If the code returns after the reset — call a pro. The control board likely needs replacement.
What it means: The cold water inlet temperature sensor has failed or has a wiring issue.
What to do: Call a pro to inspect and replace the thermistor.
What it means: The hot water outlet temperature sensor has failed.
What to do: Call a pro to test and replace the sensor.
What it means: There is a problem with the solenoid gas valve — wiring issue or component failure.
What to do: Call a pro. Involves the gas valve — do not attempt DIY.
What it means: The combustion fan has failed or its wiring is damaged.
What to do: Call a pro to inspect and replace the fan motor.
Water Flow Sensor Fault
Try Reset FirstWhat it means: The flow sensor is faulty or has a wiring issue.
What to do: Try cleaning the inlet filter first. If the code persists — call a pro.
What it means: The gas valve or its wiring has a fault.
What to do: Call a pro. Do not attempt to service gas valve components.
What it means: The flame rod isn’t detecting the flame correctly, or there’s a wiring issue.
What to do: Call a pro to clean or replace the flame rod.
Bradford White Error Codes
Tank models use LED blink codes · Tankless models use LCD display codes
Normal operation indicators: Slow green flash (once every 4 seconds) = standby, all fine. Alternating bright/dim “heartbeat” = thermostat calling for heat — normal.
Tank Models — LED Blink Codes
Ignition Lockout
Try Reset FirstWhat it means: The unit attempted to ignite and failed, then went into safety lockout. Most likely cause: pilot assembly issue, dirty thermocouple, gas supply interruption.
What to do: Attempt a manual relight per the instructions on the unit label. If lockout persists — call a pro.
Damper Circuit Fault
Try Reset FirstWhat it means: The damper test circuit isn’t working correctly, or the damper is stuck open or closed.
What to do: Verify the damper switch is set to “Automatic” and that the vent/damper is not obstructed. If it blinks again after reset — call a pro.
What it means: A variation of the damper fault, often indicating the damper failed to close properly.
What to do: Call a pro. The damper may be worn or jammed.
High Temperature Limit / Flammable Vapor Sensor Fault
Try Reset FirstWhat it means: On some models: water temperature is too high. On FVIR models: the flammable vapor sensor has detected fumes and shut down the burner as a safety measure.
What to do: If you suspect flammable vapors nearby (gasoline, solvents, paint), move those materials away and ventilate the area. Then attempt a reset. Call a pro if the code returns.
Pilot Outage or Thermopile Fault
Try Reset FirstWhat it means: The pilot light failed to stay lit, or the thermopile is weak or failed.
What to do: Attempt to relight the pilot per the label instructions. If it won’t stay lit — call a pro. A technician can test thermopile voltage.
What it means: The motorized flue damper failed to open or close as commanded.
What to do: Call a pro.
What it means: A fault has been detected in the gas control valve itself.
What to do: Call a pro. Gas control valve replacement is a job for a licensed technician.
Tankless Models — LCD Error Codes
What it means: Intake or exhaust venting is blocked or restricted.
What to do: Check the exterior vent termination for debris, nests, or obstructions. If clean — call a pro.
Ignition Failure
Try Reset FirstWhat it means: The unit attempted to fire but could not establish a flame.
What to do: Confirm the gas valve is fully open and try a power cycle reset. If the code persists — call a pro.
Flame Loss
Try Reset FirstWhat it means: The unit ignited but lost the flame.
What to do: Try a reset. If it recurs — call a pro to inspect the flame rod and gas pressure.
What it means: The heat exchanger outlet temperature exceeded safe limits.
What to do: Call a pro — the heat exchanger likely has scale buildup restricting flow.
What it means: The heat exchanger needs to be professionally flushed. Same as Rinnai LC code — unit may still run but scale is building up.
What to do: Schedule service before the unit locks out permanently. Call a pro.
Noritz Error Codes
Numeric codes on front panel · Many models emit audible beep on fault
Reset tip: Unplug the unit for 30 seconds and plug it back in. If the code returns, the underlying fault has not been resolved.
Scheduled Service Reminder
Schedule ServiceWhat it means: Not an error. The unit is due for professional maintenance.
What to do: Do not ignore or repeatedly reset this code — skipping service shortens the unit’s lifespan. Schedule a service call.
Combustion Abnormality
Try Reset FirstWhat it means: Combustion continued after the unit shut down, or combustion quality was abnormal. Most likely cause: oil, grease, or debris on the burner.
What to do: Power the unit off and back on. If the issue persists — call a pro for a burner inspection.
Ignition Failure
Try Reset FirstWhat it means: The unit cannot fire up to heat water. Most likely causes: insufficient gas supply or wrong gas type, insufficient airflow, debris on the ignition plug, wiring issue.
What to do: Verify the gas type matches the unit’s rating plate. Check the gas valve is fully open. Attempt a reset. If it doesn’t clear — call a pro.
Flame Loss
Try Reset FirstWhat it means: The unit ignited but the flame wasn’t strong enough to maintain heating. Most likely causes: low gas pressure, scale buildup on the igniter plug, poor grounding.
What to do: Check gas pressure is adequate (other gas appliances working?). Try a reset. If it recurs — call a pro.
What it means: The thermal fuse has tripped, usually due to overheating from poor water quality or restricted airflow.
What to do: Call a pro. The thermal fuse needs replacement. The heat exchanger may also need inspection.
Overheat Protection
Try Reset FirstWhat it means: The heat exchanger outlet temperature exceeded its safety limit. Most likely cause: low water flow, clogged inlet filter, or a failing heat exchanger.
What to do: Check and clean the cold water inlet filter. If the code persists — call a pro.
What it means: Similar to Code 16 but specific to the heat exchanger temperature sensor.
What to do: Call a pro. Involves heat exchanger inspection and likely descaling.
What it means: The combustion fan motor has failed or its wiring is damaged.
What to do: Call a pro to inspect and replace the fan motor.
What it means: The exhaust vent path is blocked or restricted.
What to do: Check the exterior vent for visible obstructions. If clear — call a pro to inspect the internal exhaust path.
Circuit Board Setting Error
Try Reset FirstWhat it means: The control board has an improper setting — often caused by a dip switch being changed while power was supplied.
What to do: Unplug the unit for 30 seconds and plug it back in. If the code returns — call a pro to inspect the control board.
What it means: The unit made three attempts to reach the desired temperature and failed each time — one of the most common serious Noritz codes. Most likely causes: insufficient external gas pressure, or blocked air intake, dirty combustion fan, lint or debris inside the unit.
What to do: Verify gas supply pressure. Call a pro — the internal combustion air route needs inspection and likely cleaning.
What it means: The cold water inlet temperature sensor has failed.
What to do: Call a pro to replace the thermistor.
What it means: The hot water outlet temperature sensor has failed.
What to do: Call a pro to replace the thermistor.
What it means: The temperature sensor within the heat exchanger has failed.
What to do: Call a pro.
What it means: An overheating condition was detected that didn’t resolve normally.
What to do: Call a pro. Check inlet filter first, but this usually requires professional diagnosis.
What it means: On condensing models (NRCR series): a problem with the recirculation or condensate drainage system.
What to do: Check the return line filter and crossover valve filter if accessible. Then call a pro.
GE & Whirlpool Error Codes
Tank models — pilot indicator light or LED flash codes
Normal operation: Status light blinks once every 3 seconds — no fault detected. GE and Whirlpool residential tanks are manufactured by A.O. Smith and use very similar control systems.
No Power to the Unit
Try Reset FirstWhat it means: The unit isn’t receiving power, or the gas control valve has no voltage.
What to do: Check the circuit breaker (electric models) or verify the gas supply and pilot light (gas models). If the pilot won’t light or stay lit — follow the relight instructions on the label. If unsuccessful — call a pro.
Normal Standby
Schedule ServiceWhat it means: Unit is in standby. No issue.
What to do: No action needed.
Thermopile Voltage Low
Try Reset FirstWhat it means: The thermopile (which powers the gas valve from the pilot flame) is generating insufficient voltage. Often means the pilot flame is weak or the thermopile is failing.
What to do: Verify the pilot flame is fully covering the thermopile tip. If the flame looks small or weak — call a pro to clean or replace the thermopile and pilot assembly.
High Temperature Limit / Flammable Vapor Sensor
Try Reset FirstWhat it means: Either the water temperature exceeded the safety limit, or the flammable vapor sensor detected fumes and shut the unit down.
What to do: Check for flammable materials stored near the unit (gasoline, solvents, cleaning products) and remove them. Ventilate the area. Attempt a reset. If the code returns — call a pro.
Thermal Switch Fault
Try Reset FirstWhat it means: The thermal switch (a safety device that cuts off the gas valve if the unit overheats) has tripped.
What to do: Let the unit cool completely. Attempt a reset. If it trips again — call a pro. Repeated tripping usually means an airflow or combustion problem.
What it means: The electronic gas control valve has detected an internal fault.
What to do: Call a pro. The gas control valve typically needs replacement.
Electric GE/Whirlpool Models — Common Issues
Electric tank models don’t typically use LED blink codes. Problems usually manifest as no hot water, lukewarm water, or a tripped circuit breaker.
No Hot Water / Breaker Tripping
A shorted heating element is the most common cause. Call a pro to test and replace the element.
Lukewarm Water
The upper thermostat or element has failed. Call a pro.
Water Temperature Too Hot
Try lowering the thermostat setting first. If water remains scalding — call a pro.
Quick Reference Table — All Brands
| Code | Brand | Issue | Action |
|---|---|---|---|
| 00 | Rheem | Continuous combustion | Reset; call pro if recurring |
| 05 | Rheem | Vent/air blockage | Call pro |
| 11 | Rheem | Ignition failure | Check gas + reset; call pro |
| 12 | Rheem | Flame failure | Reset; call pro |
| 14 | Rheem | Overheating | Let cool; call pro if recurring |
| 24 | Rheem | Flow sensor / clogged filter | Clean filter; call pro if persists |
| 65 | Rheem | Scale buildup | Call pro for descaling |
| E001 | Navien | Ignition failure | Reset; call pro |
| E003 | Navien | Ignition lockout | Check EQ valve; call pro |
| E012 | Navien | Flame loss | Call pro |
| E030 | Navien | Exhaust overheat | Call pro immediately |
| E110 | Navien | Low water flow | Clean filter; call pro if persists |
| 11 | Rinnai | No ignition | Check gas + reset; call pro |
| 14 | Rinnai | Thermal fuse / overheat | Call pro |
| LC | Rinnai | Scale buildup | Call pro for descaling |
| SS | Rinnai | Service reminder | Schedule maintenance |
| FF | Rinnai | Control board fault | Reset; call pro |
| 1 blink | Bradford White | Ignition lockout | Relight pilot; call pro |
| 4 blinks | Bradford White | High temp / vapor sensor | Remove flammables; call pro |
| 7 blinks | Bradford White | Gas control valve | Call pro |
| 11 | Noritz | Ignition failure | Check gas + reset; call pro |
| 90 | Noritz | Combustion abnormality | Call pro |
| LC | Noritz | Scale buildup | Call pro for descaling |
| 2 flashes | GE/Whirlpool | Low thermopile voltage | Check pilot; call pro |
| 4 flashes | GE/Whirlpool | High temp / vapor sensor | Remove flammables; call pro |
| 7 flashes | GE/Whirlpool | Gas control valve | Call pro |
Still Seeing an Error Code?
If a simple reset hasn’t resolved it, we’re here to help. We service all of the brands listed above throughout Washington, Oregon, and California (Bay Area & Southern California).
A water heater error code doesn’t always mean a costly repair or a full replacement. In many cases, a quick service call is all it takes. Don’t wait — a unit running in a fault state can cause further damage over time.
Call before noon for same-day service in most of our service areas.
Fast Water Heater Company has been serving homeowners on the West Coast since 1986. We install, repair, and replace all major water heater brands — including Rheem, Navien, Rinnai, Bradford White, Noritz, GE, and Whirlpool.
