Navien Error Code E311: Abnormal water level

The E311 error code on your Navien tankless water heater indicates that the unit's internal sensors have detected an abnormal water level. This usually means either the water level is too high or too low within the tankless unit itself. This is a safety mechanism to prevent the unit from running dry (overheating the heat exchanger) or from overflowing and damaging internal components. When this happens, the unit will lock out and stop producing hot water until the issue is resolved. This error can be triggered by a variety of factors, most commonly related to water flow, sensor issues, or problems with the unit's drain system. Because tankless units rely on precise water flow and level detection, it's important to address this issue promptly. Ignoring it could lead to further damage to the heat exchanger, pump, or other components. While some causes are simple to address, others require a qualified technician to diagnose and repair.