Warning: Your Navien boiler has detected a pump failure, which may cause system lockout and no heat.
How to Fix Navien Code E788
Check your boiler's water level and top it off if necessary, but be careful not to overfill
Listen for unusual noises from the pump, which could indicate a mechanical failure
If the boiler is still under warranty, contact Navien's customer support for assistance
How to Reset Navien Code E788
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 E788 mean?
The E788 error on your Navien boiler indicates a failure in the circulation pump. This pump is responsible for circulating hot water through your heating system. When it fails, your boiler won't be able to distribute heat, leading to a system lockout. This is a yellow hazard level because while it's not an immediate safety risk, it does require professional repair to restore heat.