Navien Error Code E799: Leak detected (sensor)
Warning: Your Navien tankless water heater has detected a leak and shut down. This requires diagnosis and repair to restore hot water.
How to Fix Navien Code E799
- Step 1: Check around the outside of the unit for any obvious signs of water leakage. Look at the pipe connections and the floor around the unit.
- Step 2: Ensure the unit's condensate drain line is properly connected and not blocked. A clogged drain can cause water to back up.
- Step 3: If you see any significant amount of water or can't identify the source, contact a qualified HVAC technician to diagnose and repair the leak.
How to Reset Navien Code E799
- Turn off the unit using the power button on the front panel.
- Turn off the gas supply valve.
- Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
- Restore power at the breaker, then open the gas valve.
- Turn the unit back on. If the error returns, the underlying issue needs repair.
What does E799 mean?
The Navien E799 error code indicates that the unit's leak detection sensor has been triggered. Navien tankless water heaters have sensors designed to detect moisture in areas where it shouldn't be, like inside the sealed burner compartment or around sensitive electronics. When the sensor detects water, the unit shuts down as a safety precaution to prevent further damage. This isn't necessarily a catastrophic failure, but it does mean that water is present where it shouldn't be, and the source of the leak needs to be identified and fixed. Ignoring this error could lead to corrosion, electrical damage, or even more serious component failures down the road.
Affected Models
- NCB-H
- NFB-H
- NFC-H
- NHB-H
- NHW-A
- NPE-A2
- NCB
- NCB
- NCB
- NPE
- NPE
- NPE
- NHB
- NHB
- NCB
- NCB
- NPE
- NPE
- NCB
- NCB
- NPE
- NCB
- NPE
- NHB
- NCB
- NPE
- NPE
- NCB
- NCB
- NPE
- NPE
- NPE
- NPE
- NHB
- NHB
- NCB
- NCB
- NPE
- NPE
- NBP
- NPE
- NPE
- NPE
- NFC
- NFC
- NCB
- NPE
- NPE
- NPE
- NCB
- NPE
- NCB
- NPE
- NPE
- NCB
- NPE
- NHB
- NPE-S
- NPN
- NPN
- NCB
- NPE
- NCB
- NPE
- NHB
- NPB
- NFC
- NFC
- NHB
- NPF
- NPF
- NPE
- NHB
Source Documentation
| Manual | Page | Reason | Action |
|---|---|---|---|
| Navien NPF Installation & Operation Manual | 128 | Leak detected (sensor) | This error occurs when a leak occurs in the furnace. ● Open the lower-front cover and check for leaks in the furnace. ● If you find any leaks in the furnace, contact Technical Support at 1-800-519-8794. |
Replacement Parts
| Part | OEM Number | Est. Cost |
|---|---|---|
| Leak Detection Sensor | 30014522A | — |
| Heat Exchanger Assembly | — | — |
| Condensate Drain Assembly | — | — |
Related Codes on Same Models
| Code | Description | Severity |
|---|---|---|
| E001 | Ignition Failure | Warning |
| E003 | Abnormal Ignition | Warning |
| E004 | False Flame Detection | Warning |
| E012 | Flame Loss | Warning |
| E016 | Overheating | Warning |
| E030 | Exhaust Overheat Sensor | Warning |
| E031 | Inlet Thermistor Open/Short | Warning |
| E046 | Outlet Thermistor Open/Short | Warning |
| E047 | DHW Thermistor Open/Short | Warning |
| E060 | Fan Motor Abnormality | Warning |