Brand guide
All Navien water heater guides
Choose the symptom or code that matches your unit. Confirm the exact model and control generation against the rating plate before following model-specific instructions.
Navien Condensate Drain Leaking
A wet Navien condensate fitting is a trap, slope, freeze, or loose union — not always a dead exchanger. Fix the drain path first.
Leaks and floodingNavien Constantly Running: Recirc or Leak
A Navien that never seems to stop is usually the recirculation pump. If the burner itself keeps firing, suspect a stuck flow sensor or a leak.
Error codes and flashing lightsNavien Dead After a Power Outage
A Navien that won't heat after a power outage may have a tripped GFCI, a display set to Off, a lockout code, or freeze damage. What to check.
TanklessNavien DHW Wait: Why Hot Water Is Late
A long wait for Navien hot water is usually pipe length, recirculation turned off, or a combi unit prioritizing heat. How to time and diagnose it.
Pilot and ignition problemsNavien E003: Ignition Failure Lockout
Navien E003 means ignition failure: the unit tried to light and never proved flame. Common causes, a safe reset, and when to call a pro.
Error codes and flashing lightsNavien Error 598-00: RTC / Display Fault
Navien error 598-00 is a real-time clock fault on the front display board, not a heating failure. What to try and when the display needs replacing.
Gas, burning, and sulfur smellsNavien Exhaust Smells Like Gas? Leave
Gas odor at a Navien termination is an emergency. Leave and call the gas utility from outside; do not restart the unit.
No hot waterNavien Goes Cold After a Few Minutes
A Navien that goes cold after a few minutes usually has low flow, a recirculation cold slug, flame loss (E012), or scale overheating (E016).
Pilot and ignition problemsNavien Knocking Noise: What It Means
Distinguish when a Navien knocks: during ignition, water flow, or heating. Record the pattern and recognize when the unit needs service.
Leaks and floodingNavien Leaking From the Bottom
Bottom drip on a Navien is condensate, a fitting, the PRV, or a heat exchanger. Identify the fluid, then shut it down.
TanklessNavien Low Pressure? Find the Restriction
Navien low hot-water flow is a clogged inlet filter, scale, valves, or undersize — not a booster setting. Diagnose it.
TanklessNavien Tankless Vibration Under Fire
A Navien that vibrates while firing is usually the recirculation pump, combustion fan, scale, or loose mounting. How to identify the source.
Gas, burning, and sulfur smellsNavien Tankless Water Heater Exhaust Blockage
A blocked Navien exhaust can cause a lockout, gas odor, or no heat. Check the termination from outside.
TanklessNavien Tankless With No Water Flow
No water through a Navien usually means closed isolation valves, a clogged inlet filter, scale, a failed mixing valve, or frozen pipes.
Error codes and flashing lightsNavien Water Heater Error 773-00
Navien 773-00 points to a model-specific control or communication fault. Photograph the display, power-cycle once.
No hot waterNavien Water Heater Not Getting Hot
A Navien that never reaches its set temperature may be undersized, scaled, limited by a mixing valve, crossed over, or short on gas supply.
TanklessNavien Water Heater Not Turning On
A Navien that won't turn on usually has no 120 V, a display set to Off, no flow signal, or a lockout. Safe checks before calling a technician.