USA Expert Plumbing

Navien tankless water heater maintenance: a yearly checklist

By USA Expert Plumbing Editorial Team. Updated . 2 min read.

Short answer

Navien condensing tankless heaters need a yearly checkup: flush the heat exchanger to remove scale, clean the cold water inlet filter, clean the intake air filter, and check the condensate drain, neutralizer and venting. Several Navien codes, including E016, E109 and E110, point straight back to skipped maintenance.

In this guide
  1. How often
  2. Codes that point to maintenance
  3. How to flush a Navien
  4. The intake air filter
  5. Condensate and neutralizer
  6. Recirculation models
  7. Winter

Most Navien heaters sold in the U.S. are condensing units, which squeeze extra heat out of the exhaust. That design is efficient but adds maintenance items a basic tank does not have: an air filter, a condensate drain and a neutralizer.

How often

TaskHow often
Flush (descale) the heat exchangerAbout once a year; more often with hard water
Clean the cold water inlet filterAt every flush, or when flow drops
Clean the intake air filterSeveral times a year in dusty spaces
Check the condensate drain and neutralizerAt every service
Check the vent terminals outsideEvery season, and after storms or snow

Codes that point to maintenance

  • E016 (heat exchanger overheating) and E030 (exhaust overheating): Navien's manual tells owners to clean the inlet filter and flush the heat exchanger.
  • E109 (fan motor): the first step is cleaning the intake air filter.
  • E110 (air or exhaust blocked): check the vent and clean the intake air filter.

How to flush a Navien

Navien heaters are typically installed with isolation valves that have service ports. The general sequence is:

  1. Turn off the heater at its controller, disconnect power and close the gas supply valve.
  2. Close the hot and cold isolation valves under the unit.
  3. Connect a small submersible pump and hoses to the service ports, with the pump sitting in a bucket of white vinegar or a descaling solution approved by the manufacturer.
  4. Open the service ports and circulate the solution through the heat exchanger for the time your manual specifies, usually about an hour.
  5. Drain the solution, then flush with clean water.
  6. Close the service ports, clean the inlet filter, open the isolation valves and purge air from a hot tap before restoring gas and power.

Always follow your Navien manual for your model. Our guide to descale a tankless water heater covers the job in more detail.

The intake air filter

Condensing Navien units draw combustion air through a filter. In a garage, laundry room or workshop it can clog with lint and dust surprisingly fast, which leads to fan and combustion codes. Turn off and unplug the unit, remove the filter as the manual shows, rinse or clean it, let it dry and reinstall it.

Condensate and neutralizer

  • Make sure the condensate line runs downhill and drains freely, and protect it from freezing.
  • Replace the neutralizer media when it is used up; spent media can restrict flow.

Recirculation models

If your Navien has a built-in recirculation pump, keep all supply and return valves fully open. A closed valve or air in the loop is a common cause of E438.

Winter

Navien's freeze protection needs power. See our guide to tankless water heater freeze protection for what to do in an outage.

See all codes on our Navien error codes page.

Common questions

How often should a Navien tankless be flushed?

About once a year for most homes, and more often with hard water.

Where is the air filter on a Navien?

On condensing NPE models it sits at the air intake on or in the unit. The manual shows the exact location for your model.

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