How To Fix Navien Water Heater: Your Step-By-Step Troubleshooting

There’s nothing quite like the shock of a cold shower when you’re expecting a warm, relaxing stream of water. Your high-efficiency Navien tankless water heater, usually a silent hero, is suddenly the source of frustration. You might see a confusing error code flashing on its digital display, or maybe you’re just getting lukewarm water—or none at all.

I hear this from homeowners all the time. But before you reach for the phone to schedule an expensive service call, I want to promise you something: you can solve many of these issues yourself. As an HVACR technician, I can tell you that understanding the basics of how to fix Navien water heater problems is well within your reach.

In this guide, we’ll walk through everything together. We’ll start with essential safety checks, decode those cryptic error codes, tackle the most common problems step-by-step, and cover the preventative maintenance that keeps your unit running smoothly. Think of me as your virtual tech, here to help you get that hot water flowing again.

Before You Begin: Safety First and Essential Tools

Alright, before we roll up our sleeves, let’s talk about the most important step: safety. We’re dealing with gas, water, and electricity. Taking a moment to prepare properly isn’t just a good idea—it’s non-negotiable.

Your Safety Checklist

Always perform these steps before touching your unit:

Turn Off the Power: Locate the circuit breaker for your water heater in your home’s electrical panel and switch it to the OFF position. Some units may also have a power switch directly on or near the heater.
Shut Off the Gas: Find the gas shutoff valve on the line leading to your Navien unit. The handle should be perpendicular (forming a “T”) to the pipe to be in the OFF position. If you ever smell gas, stop immediately, leave the house, and call your gas company from a safe distance.
Close the Water Valves: Your unit will have three valves on the pipes connected to it: a cold water inlet (blue), a hot water outlet (red), and the main gas line (yellow). Turn the handles on the hot and cold water lines so they are perpendicular to the pipes to stop water flow.

Tools You’ll Need

You won’t need a full workshop, but having a few basic tools on hand will make these checks much easier. This is part of the how to fix navien water heater best practices.

A bucket and some old towels (water is bound to spill)
A Phillips head and a flathead screwdriver
A pair of channel-lock pliers
An old toothbrush for cleaning small parts
Your Navien water heater user manual (if you can’t find it, you can usually download a PDF from Navien’s website)

Decoding Navien Error Codes: What Your Heater is Telling You

One of the best things about Navien units is their built-in diagnostics. That little error code is your first clue. It’s the heater’s way of telling you exactly where to start looking. Let’s cover some of the most common problems with how to fix Navien water heater diagnostics.

Common Error Code E001 (Overheating)

This code means the unit’s internal temperature has exceeded a safe limit. It’s often caused by restricted water flow, usually from mineral buildup (scaling) or a clogged filter.

What to do: Turn the power off, wait 30 minutes for it to cool, and then check and clean the inlet water filter (we’ll cover how to do that below). If the error persists after cleaning, you likely need to descale the unit.

Common Error Code E010 (Air Pressure/Exhaust Blockage)

Your Navien needs to breathe. This code indicates a problem with the air intake or the exhaust vent. It’s a safety feature to prevent dangerous flue gases from entering your home.

What to do: Safely go outside and visually inspect the intake and exhaust vent pipes. Look for obstructions like bird nests, leaves, snow, or insect hives. Carefully clear away any debris you find.

Common Error Code E110 (Ignition Failure)

This means the unit tried to light the burner but failed. The most common cause is a simple lack of gas.

What to do: First, ensure your main gas valve and the valve leading to the unit are fully open. Check if other gas appliances in your home (like a stove) are working. If they are, and the error continues, this points to an internal component like the igniter or gas valve, and it’s time to call a professional.

Your Step-by-Step Guide on How to Fix Navien Water Heater Problems

Error codes are a great starting point, but sometimes the unit just isn’t behaving correctly without giving you a code. Let’s get into the specifics of how to how to fix navien water heater symptoms with this practical guide.

Problem: No Hot Water at All

This is the most alarming issue, but often the easiest to fix. Don’t panic; just work through this checklist.

Check the Display: Is the unit powered on? If the screen is blank, move to the next step. If it shows an error code, refer to the section above.
Verify Power: Go to your circuit breaker panel. Find the breaker for the water heater and see if it has tripped. If it has, flip it firmly to the OFF position, then back to ON.
Confirm Gas Supply: Make sure the gas valve handle is parallel to the pipe (in the ON position).
Check Water Valves: Ensure both the cold inlet and hot outlet valves are open (handles parallel to the pipes). Someone may have closed them and forgotten to reopen them.

Problem: Water Isn’t Hot Enough (Lukewarm Water)

Getting lukewarm water is frustrating. It usually points to a flow issue or a simple setting adjustment.

Check the Temperature Setting: Someone may have lowered the temperature on the unit’s front panel or the remote control. Navien recommends a setting between 120°F and 125°F for most homes.
Inspect the Inlet Water Filter: This is a huge culprit. A clogged filter restricts the amount of water entering the unit, and it can’t heat what it doesn’t receive. We’ll detail how to clean this in the maintenance section.
Consider Mineral Buildup: If it’s been over a year since your unit was flushed (descaled), mineral buildup inside the heat exchanger could be insulating it, preventing it from transferring heat effectively to the water.

Problem: Fluctuating Water Temperatures

If your shower goes from hot to cold and back again, it’s often caused by something disrupting the unit’s ability to maintain steady flow and firing.

Clean Your Fixture Aerators: Unscrew the tips of your faucets and showerheads. If the small screens are clogged with sediment, it can cause the flow rate to drop too low, making the heater shut off. A quick cleaning with an old toothbrush often solves this.
Check Minimum Flow Rate: Tankless heaters need a minimum amount of water flowing through them to activate. If you’re just barely turning on a single faucet, you might be below that threshold. Try opening the faucet a little more to see if the temperature stabilizes.

The Secret Weapon: A Proactive Maintenance Care Guide

The absolute best way to fix your Navien water heater is to prevent it from breaking in the first place. Following this simple how to fix navien water heater care guide will dramatically extend its life and efficiency. These are the sustainable and eco-friendly how to fix navien water heater practices that also save you money.

Annual Flushing (Descaling): The Most Important Task

Think of this like an oil change for your water heater. Mineral deposits (scale) from your water build up inside the delicate passages of the heat exchanger. This forces the unit to work harder, reduces efficiency, and can lead to overheating failures.

Flushing involves circulating a vinegar or a descaling solution through the unit using a small pump and hoses. While it’s a DIY-friendly task, it requires some specific equipment. If you’re not comfortable, a technician can perform this service for you. Doing this annually is one of the most important how to fix navien water heater tips I can give.

Cleaning the Inlet Water Filter

This simple task can solve a surprising number of problems and should be done every 6 months.

Follow the safety steps to turn off power, gas, and water.
Place a bucket under the cold water inlet connection.
Unscrew the plug on the bottom of the cold water line connection. Water will drain out.
Behind the plug, you’ll find a small screen filter. Gently pull it out with pliers.
Rinse the filter under a faucet and use a toothbrush to remove any sediment.
Reinsert the filter and tighten the plug. Turn your water back on slowly and check for leaks before restoring power.

When to Put Down the Tools and Call a Professional

Empowerment is great, but wisdom is knowing your limits. Your safety is paramount. Please call a licensed and certified Navien technician if you encounter any of the following situations:

You smell gas at any time. Do not hesitate. This is an emergency.
You are getting persistent error codes that the manual’s troubleshooting steps don’t resolve.
The problem requires opening the main cover of the unit to access internal components like the motherboard, gas valve, or fan.
You see water leaking from the body of the unit itself, not just from the pipe connections.
You are simply not comfortable performing any of the steps outlined here. There is no shame in calling for expert help!

Frequently Asked Questions About Fixing a Navien Water Heater

How often should I flush my Navien tankless water heater?

For most homes with average water hardness, flushing your unit once a year is perfect. If you live in an area with very hard water, you may benefit from doing it every 6 to 9 months to prevent heavy scale buildup.

Why is my Navien water heater making a loud noise?

A rumbling or “kettling” noise is almost always caused by scale buildup on the heat exchanger. The sound is water boiling and popping against the super-heated mineral deposits. Flushing the unit will usually solve this. If it’s a high-pitched whining, it could be related to the fan and may require a technician.

Can I reset my Navien water heater?

Yes. The simplest way to reset the unit is to power it off using the button on the front panel, wait 30 seconds, and turn it back on. For a “hard reset,” you can turn off its circuit breaker for about a minute. This can clear temporary electronic glitches but won’t fix a mechanical problem.

What are the benefits of how to fix navien water heater issues myself?

The biggest benefit is cost savings on service calls for simple issues. It also empowers you to understand your home’s systems better, allowing you to spot small problems before they become big ones and perform the preventative maintenance that keeps your heater running efficiently for years to come.

Tackling these fixes can be incredibly rewarding. By following these steps safely and methodically, you’ve taken control of your home’s comfort. You’ve learned how to listen to what your heater is telling you and how to respond. You’ve got this!

Stay safe, stay warm, and enjoy that reliable 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.