Navien Tankless Water Heater Error Code - Your DIY Troubleshooting

There’s nothing quite like the jolt of a cold shower when you were expecting a hot one. You head to your Navien tankless unit and see it—a small, blinking number on the digital display. That sinking feeling is a familiar one for many homeowners, but don’t worry. That little display is your water heater’s way of talking to you, and we’re here to help you translate.

We know how frustrating it is to be faced with a cryptic navien tankless water heater error code when all you want is reliable hot water. That’s why we’ve created this guide.

We promise to walk you through what these codes mean, which ones you can safely troubleshoot yourself, and when it’s time to call in a professional. You’ll learn how to identify the problem, perform basic checks, and get your hot water flowing again.

In this guide, we’ll cover the most common error codes, provide a step-by-step navien tankless water heater error code guide for diagnostics, and share best practices to keep your unit running smoothly for years to come. Let’s get started.

First Things First: Understanding Your Navien’s Display and Basic Safety

Before you touch anything, let’s get familiar with your unit and cover some critical safety rules. Think of this as your pre-flight check. Your safety is always the number one priority.

Most Navien units have a simple front panel with an LCD screen and a few buttons. The screen will display the current water temperature and, when there’s a problem, the error code. The buttons typically allow you to adjust the temperature and reset the unit.

Safety Precautions to Take Before Troubleshooting:

Smell Gas? Stop Immediately. If you ever smell natural gas or propane (a rotten egg smell), leave the area immediately. Do not use your phone, turn lights on or off, or unplug anything. From a safe distance, call your gas utility’s emergency line and a qualified HVACR professional.
Turn Off the Power. For many checks, you’ll want to kill the power to the unit. You can do this at your home’s circuit breaker panel. This prevents any electrical risk while you’re inspecting components.
Know Your Shut-Offs. Be familiar with the location of the main water and gas shut-off valves for your water heater. If you ever have a major leak, you’ll need to turn the water off quickly.

Decoding Your Navien Tankless Water Heater Error Code: A Comprehensive Guide

Alright, with safety covered, let’s dive into the codes themselves. We’ve grouped the most common problems with Navien tankless water heater error codes into categories to make them easier to understand. We’ll explain what they mean and what you can do about them.

Common Ignition & Flame Error Codes (e.g., E003, E012)

These codes mean the unit is trying to light the burner but is failing to do so. It’s like a car that cranks but won’t start. This is often one of the most frequent issues homeowners face.

What it means: The system is not detecting a stable flame after trying to ignite.

DIY Checks You Can Perform Safely:

Check Your Gas Supply: This might sound obvious, but it’s the first place to look. Is your gas valve to the unit open? Is your home’s main gas meter on? If you have other gas appliances (like a stove), check if they are working. If they aren’t, you have a larger gas supply issue.
Inspect the Condensate Drain: High-efficiency units like Navien produce condensation. If the condensate drain line gets clogged or frozen, a safety switch will prevent the unit from firing. Ensure the small plastic tube leaving the bottom of the unit is clear and draining properly.
Power Cycle the Unit: Sometimes, a simple reset is all it takes. Turn the power off to the unit at the breaker, wait a full minute, and turn it back on. This can clear a temporary fault.

When to Call a Pro: If you’ve checked these items and the code persists, or if you suspect a gas supply issue, it’s time to call a technician. The problem could be a faulty igniter, a flame sensor, or a gas valve, which all require professional service.

Exhaust & Venting Error Codes (e.g., E009, E010)

Your tankless water heater needs to breathe. It pulls in fresh air for combustion and pushes out exhaust fumes. These codes indicate a problem with that airflow, often related to the vent pipes or the internal fan.

What it means: There’s an issue with the air pressure switch, indicating improper venting or a blocked exhaust/intake.

DIY Checks You Can Perform Safely:

Inspect Exterior Vents: Go outside and look at where your PVC vent pipes terminate. Are they blocked by leaves, snow, bird nests, or debris? Clear away any obstructions carefully.
Check for Water in the Vents: Ensure the horizontal vent pipes are sloped slightly back towards the unit. This allows condensation to drain properly. Improper sloping can cause water to pool and trigger a pressure switch error. This is a key part of an eco-friendly navien tankless water heater error code strategy, as proper venting ensures maximum efficiency.

When to Call a Pro: If the vents are clear and the error continues, the issue is likely internal. It could be a failing vent fan motor or a bad pressure switch, both of which need a certified technician to diagnose and replace.

Water Flow & Pressure Error Codes (e.g., E001, E110)

These codes are all about water—either not enough of it is flowing through the unit, or the pressure is too low for it to operate safely. This is one of the most common and often easiest issues for a DIYer to fix.

What it means: Low water pressure or a flow sensor issue is preventing the unit from activating.

DIY Checks You Can Perform Safely:

Check Your Water Valves: Make sure the main water valve to your house and the shut-off valve on the cold water inlet pipe to the Navien are fully open.
Clean the Inlet Water Filter: This is a big one! There is a small screen filter on the cold water inlet of your Navien. Over time, it can get clogged with sediment. Turn off the water supply, unscrew the connection, carefully remove and clean the filter with a small brush, and reinstall it.
Clean Faucet Aerators: If you only experience the issue at one sink, the problem is likely a clogged aerator on that faucet. Unscrew it and clean out any debris.

When to Call a Pro: If you have good water pressure throughout your house and have cleaned the filters, the problem might be an internal flow sensor that needs professional attention.

How to Reset Your Navien Water Heater After an Error Code

Once you’ve addressed the potential cause of an error, you’ll often need to reset the unit to clear the code. Knowing how to navien tankless water heater error code reset works is a simple but powerful step.

For most Navien models, the process is straightforward:

Resolve the Underlying Issue: A reset won’t help if the problem (like a blocked vent) still exists. The code will just come right back.
Use the Reset Button: Press the “Reset” button on the front control panel. On some remote controllers, you may need to press the power button off and then on again.
Perform a Power Cycle: If the button doesn’t work, use the breaker method. Turn the power off at your circuit breaker, wait 60 seconds, and then turn it back on. This performs a “hard reset” of the unit’s electronics.

Preventative Maintenance: Best Practices to Avoid Future Error Codes

The best way to deal with an error code is to prevent it from ever happening. A little routine care goes a long way. This is your ultimate navien tankless water heater error code care guide.

Following these navien tankless water heater error code best practices will extend the life of your unit and improve its efficiency.

Annual Descaling (Flushing): If you live in an area with hard water, mineral scale (lime and calcium) will build up inside your unit, restricting flow and damaging components. Flushing the unit annually with a descaling solution is the single most important maintenance task you can perform.
Clean the Inlet Filter Regularly: As mentioned above, make it a habit to check and clean the cold water inlet filter every 6-12 months.
Keep Vents Clear: Periodically check your exterior vents to ensure they remain free of blockages. This promotes both safety and efficiency, contributing to a more sustainable navien tankless water heater error code-free operation.

When to Put Down the Tools and Call a Certified Navien Technician

While many codes can be resolved with simple checks, some situations absolutely require a professional. Your safety and the health of your expensive equipment depend on knowing your limits.

Call a licensed and certified Navien technician immediately if you encounter any of the following:

You smell gas at any point.
The same error code returns immediately after you reset it.
You see signs of water leaking from inside the unit’s casing.
The error code points to an internal component like a gas valve, circuit board, or heat exchanger.
You are not 100% confident in performing any of the DIY checks. There is no shame in calling for help!

Frequently Asked Questions About Navien Tankless Water Heater Error Codes

Why does my Navien keep showing an error code?

A recurring error code means the underlying problem has not been fixed. For example, if you keep getting a vent blockage code (E010) and reset it without clearing the actual nest from the pipe, the code will just keep coming back. It’s a sign to investigate the root cause, not just the symptom.

Can I clear an error code myself?

Yes, you can clear a code by resetting the unit using the front panel button or by power cycling it at the breaker. However, this should only be done after you have identified and corrected the cause of the fault. Simply clearing the code without fixing the problem is only a temporary fix.

How much does it cost to fix a Navien error code?

The cost varies dramatically. A fix you can do yourself, like cleaning a filter or unblocking a vent, costs nothing but your time. A service call from a technician might cost $100-$300 just for the diagnosis. If a major part like a control board or fan motor needs replacing, the total cost could range from $400 to over $1,000.

Is error code E010 on a Navien serious?

Error code E010 indicates an abnormal exhaust or air supply issue. It can be serious because it means your unit isn’t venting properly, which could be a safety hazard. While the cause can be as simple as a blocked vent pipe, it should be addressed immediately. The unit’s safety features will typically shut it down until the issue is resolved.

Dealing with a navien tankless water heater error code can feel daunting, but it doesn’t have to be a crisis. By understanding what your unit is telling you and following these safe, simple steps, you can solve many common problems yourself. Remember to prioritize safety, perform regular maintenance, and don’t hesitate to call a trusted professional when you’re in over your head.

You’ve got this! Stay safe, stay informed, and enjoy that endless hot water.

Author
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David Clark

Founder & Lead HVAC Specialist at HVACRLY

David Clark is the founder of HVACrly and a certified HVAC specialist with 10+ years working on residential and light-commercial systems. He turns complex heating, cooling, ventilation, and refrigeration topics into clear, actionable guides focused on safety and energy efficiency. When he’s not on a service call, he’s testing tools and writing step-by-step tutorials.