Navien Water Heater Issues – Your Ultimate Troubleshooting Guide

There’s nothing quite like the jolt of an unexpectedly icy shower to ruin your morning. You invested in a high-efficiency Navien tankless water heater for its promise of endless hot water, and for a while, it was perfect. Now, you’re facing lukewarm water, strange noises, or a frustrating error code on that little screen. It’s a moment we see all the time.

I get it. That feeling of “what now?” can be stressful. But here’s the good news: many common navien water heater issues can be diagnosed and sometimes even fixed with a little know-how. You’ve come to the right place for that expert guidance.

We promise this comprehensive guide will walk you through the most frequent problems, from simple resets to critical maintenance steps. You’ll learn how to understand what your heater is telling you, perform safe DIY checks, and recognize exactly when it’s time to call in a certified technician for backup.

Let’s dive in and get that hot water flowing again.

Decoding the Dreaded Navien Error Codes: What Your Unit is Telling You

One of the best features of a Navien unit is its self-diagnostic system. That little error code is your first clue. Instead of panicking, think of it as your water heater trying to talk to you. Here are some of the most common codes we encounter in the field.

Error Code E110 (or 110): Exhaust Overheating / Blockage

This is one of the most frequent codes. It means the exhaust system is getting too hot, which is a safety feature to prevent damage or a fire hazard. Don’t worry—it’s usually a simple fix.

What it means: The venting is likely blocked. This could be from a bird’s nest, snow, leaves, or other debris in the exhaust pipe outside your home.
Your first check: Safely inspect the exterior vent termination. Is it clear of obstructions? Sometimes, strong winds can dislodge the vent pipe connection inside, too.
The pro step: If the vent is clear and the code persists, it could be a sign of an internal blockage or a faulty sensor, which requires a technician.

Error Code E003: Ignition Failure

This code tells you the unit tried to light the burner three times and failed. It’s essentially saying, “I can’t start the fire to heat your water.”

What it means: The problem could be with the gas supply, the igniter itself, or the flame sensor.
Your first check: The simplest thing to check is your gas supply. Is the gas valve to the unit turned on? Is your home’s main gas supply active? Check other gas appliances (like your stove) to confirm.
The pro step: If gas is flowing, the issue is likely internal—a dirty flame sensor, a bad igniter, or a faulty gas valve. These components require a professional to service safely. Never attempt to service gas components yourself.

Error Code E012: Flame Loss

This code means the unit successfully ignited but the flame went out while it was running. It’s a frustrating issue that leads to fluctuating water temperatures.

What it means: This can be caused by irregular gas pressure, a dirty flame sensor that can’t “see” the flame, or a problem with the condensate drain.
Your first check: Ensure the condensate drain line isn’t clogged or frozen. If this line backs up, it can extinguish the flame as a safety measure.
The pro step: This often points to gas pressure issues that need to be measured and adjusted by a licensed technician with a manometer.

The “No Hot Water” Panic: Common Problems with Navien Water Heater Issues

Sometimes, the unit doesn’t give you an error code—it just gives you cold water. This is where we need to play detective. Most common problems with navien water heater issues start with water flow or ignition.

Flow Rate & Water Pressure Problems: The “Low Flow” Culprit

Navien tankless heaters require a minimum flow rate to activate—usually around 0.5 gallons per minute (GPM). If the flow is too low, the heater won’t even try to turn on.

Think of it like a car that won’t start unless the key is turned all the way. A weak flow of water won’t “turn the key” for your heater.

DIY Checks:

Open the Tap Fully: Are you only cracking the hot water handle slightly? Try opening it all the way to see if it triggers the heater.
Check Faucet Aerators: Unscrew the aerators on your faucets and check for mineral buildup or debris. A clogged aerator can restrict flow enough to prevent the heater from activating.
Clean the Inlet Filter: Your Navien has a small filter on the cold water inlet pipe. Turn off the water, unscrew it, and clean out any sediment. This is a huge and often overlooked cause of flow problems.

Ignition Failure Without a Code

If you have good water flow but still hear nothing from the unit—no click, no fan—the problem could be more fundamental.

Your first check: Is the unit plugged in and receiving power? Check your breaker panel. It sounds simple, but you’d be surprised how often a tripped breaker is the culprit. Ensure the power button on the unit itself is on.

Gas Supply Interruptions

As we mentioned with the E003 code, no gas means no flame. If your gas has been shut off for any reason (e.g., utility work in the area) and then turned back on, you may need to purge the air from the gas lines by running another appliance like your stove for a minute before the Navien will successfully ignite.

Your Navien Water Heater Issues Care Guide: Proactive Maintenance to Prevent Breakdowns

The absolute best way to handle navien water heater issues is to prevent them from happening in the first place. This is where our navien water heater issues care guide comes in. Proper maintenance not only extends the life of your unit but also keeps it running efficiently, which is key for a sustainable and eco-friendly navien water heater issues solution.

Annual Flushing: Fighting Scale Buildup

If you live in an area with hard water, mineral scale (calcium and magnesium) is your heater’s worst enemy. This scale builds up inside the delicate pipes of the heat exchanger, restricting flow and forcing the unit to work harder.

Flushing your unit annually with a vinegar solution using an isolation valve kit is one of the most important navien water heater issues best practices. This descaling process dissolves the buildup and restores performance.

Cleaning the Inlet Water Filter and Air Filter

We mentioned the inlet water filter for flow issues, but it’s also a key maintenance item. Clean it every 6-12 months. Additionally, the unit has an air intake filter or screen. A clogged air filter starves the burner of oxygen, leading to poor combustion and potential shutdowns.

Checking the Condensate Drain

Navien units are high-efficiency condensing heaters. This means they produce acidic condensation that must be drained away. Ensure the drain line is clear, unobstructed, and not frozen during winter months. A blocked line will shut the unit down to prevent water damage.

How to Navien Water Heater Issues: A Step-by-Step DIY Troubleshooting Checklist

Feeling ready to tackle some basic checks? Here is a simple, safe checklist to run through before calling a pro. This how to navien water heater issues guide can save you time and money.

Check the Display: Is there an error code? Write it down. This is the most valuable piece of information you can have.
Confirm Power: Is the unit plugged in? Is the power button on? Check the circuit breaker in your electrical panel.
Verify Gas Supply: Ensure the gas valve leading to the water heater is in the “On” position (parallel to the pipe). Check other gas appliances in your home.
Inspect Vents: Look at the intake and exhaust vents outside. Are they completely clear of snow, leaves, nests, or other debris?
Check Water Flow: Open multiple hot water taps fully. If the pressure seems low, clean your faucet aerators and the unit’s inlet water filter.
Examine the Condensate Line: Make sure the small plastic tube leaving the bottom of the unit is not kinked, clogged, or frozen.
Perform a Reset: The simplest of all navien water heater issues tips. Unplug the unit from the wall, wait 30 seconds, and plug it back in. This can often clear temporary faults.

When to Put Down the Tools: Knowing When to Call a Certified Navien Technician

While DIY checks are empowering, some situations are non-negotiable and require a licensed professional. Your safety is always the top priority.

Call a pro immediately if you encounter any of the following:

You Smell Gas: If you smell gas near the unit or anywhere in your home, leave the house immediately, then call your gas utility company and an HVAC professional from a safe location. Do not operate any electrical switches or try to unplug the unit.
Error Codes Persist After a Reset: If you’ve reset the unit and cleared any obvious blockages but the error code returns, it points to a faulty internal component.
The Unit is Leaking Water: While a drip from a fitting might be a simple tightening job, any water coming from the casing of the unit itself indicates a serious internal failure.
You Need to Open the Casing: Any troubleshooting that requires removing the front cover to access the burner, gas valve, or electronics should be left to a trained and certified technician.

Frequently Asked Questions About Navien Water Heater Issues

Why does my Navien water heater keep turning off?

This is often caused by “flame loss” (Error E012), which can result from a clogged condensate drain, fluctuating gas pressure, or a dirty flame sensor. It can also happen if the exhaust vent is partially blocked, causing the unit to overheat and shut down as a safety precaution.

How often should I service my Navien tankless water heater?

We strongly recommend professional service once a year. However, the most critical maintenance—descaling or flushing the unit—depends on your water hardness. In areas with very hard water, you may need to do it every 6-9 months. For softer water, every 12-18 months may suffice.

Can I reset my Navien water heater myself?

Absolutely. The easiest way to perform a “soft reset” is to simply unplug the unit from the electrical outlet, wait about 30 seconds, and plug it back in. This will clear any temporary electronic glitches without erasing any fault history, which is useful for a technician if the problem continues.

Tackling navien water heater issues can feel daunting, but by following this guide, you are now equipped with the knowledge to handle the basics with confidence. You understand what your heater is telling you, you know the safe checks to perform, and most importantly, you know the signs that mean it’s time to call for professional help.

Remember, regular maintenance is the key to enjoying years of reliable, on-demand hot water. Taking care of your Navien unit is taking care of your home’s comfort and efficiency.

Stay safe, stay comfortable, and here’s to many more hot showers!

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.