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Navien tankless water heater code E762: Vent pipe not fully inserted

Tankless water heater, Canada and United States

The heater's vent installation detector sensed that the exhaust pipe is not fully seated in the vent collar, so the heater will not run. Navien notes that this detector does not catch joints that separate elsewhere and is no substitute for a carbon monoxide alarm.

This needs a licensed gas technician. There is nothing safe to check yourself. Leave the covers on and book a professional.

This involves the flue or exhaust. A blocked or leaking flue can let carbon monoxide into the home.

What causes it

Canadian and US models

  1. The vent pipe is not pushed at least 2 3/4 in. (70 mm) into the vent collar, so it does not press the detector switch.

    Book a licensed gas technician

  2. The vent pipe is the wrong size (the collar takes 2 in. pipe), deformed or misaligned, or it has moved since installation.

    Book a licensed gas technician

US models

  1. The vent pipe is not fully seated in the heater's vent connection, or it has moved since installation.

    Book a licensed gas technician

How to read this code on your unit

Booking a licensed gas technician

Contact Navien before booking a repairYou can do this

  1. Have the model number, serial number, purchase date, where the heater is installed and the error code ready.
  2. Call Navien Technical Support on 1-800-519-8794, or contact the company that installed the heater.
  3. For a repair under warranty, the installer or service provider must contact Navien before starting the work.

Book a licensed gas technicianlicensed gas technician

  1. Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
  2. Note the code, how often it appears, and the model and serial numbers from the rating label.
  3. Book a licensed gas technician and give them those details.

Models that show this code

14 models in 4 ranges
RangeModels
NPE-A2NPE-180A2, NPE-210A2, NPE-240A2
NPE-S2NPE-180S2, NPE-210S2, NPE-240S2, NPE-150S2
NPN-ENPN-120E, NPN-160E, NPN-180E, NPN-199E
NPN-UNPN-160U, NPN-180U, NPN-199U

Where this comes from

Checked against the manufacturer's manual on 9 October 2026.

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Other Navien tankless water heater codes

Code Meaning What you can do
E110 Abnormal air pressure (blocked vent or intake filter) Safe checks first, then a pro
E127 Air volume sensor fault Call a pro
E157 Air volume control fault Call a pro
E594 Memory chip (EEPROM) fault Call a pro
E615 Input and memory fault Call a pro
E736 Cascade communication fault Call a pro
E740 Outdoor temperature sensor fault Call a pro
E760 Flushing or service reminder Call a pro
E773 Wrong gas type detected or gas connection fault (depends on model) Call a pro
E782 Main panel communication fault Call a pro
E785 Flow switch or sensor fault Call a pro
E786 Panel connection fault Call a pro

See all flue or venting fault codes on tankless water heaters across brands.