Navien Tankless Water Heater External Exhaust Blockage Error 110 01

There’s nothing quite like the jolt of a suddenly cold shower to ruin your morning. You check your Navien tankless unit, and there it is: a flashing error code. You’ll agree that seeing a technical warning when you just want hot water is incredibly frustrating.

We promise this guide will demystify one of the most common alerts—the navien tankless water heater external exhaust blockage error 110 01. This isn’t just a random number; it’s your water heater’s way of telling you it can’t breathe properly, and it has shut down to keep you safe.

In this comprehensive guide, we’ll walk you through what this error means, its most common causes, and a safe, step-by-step inspection you can perform yourself. We’ll also cover when it’s absolutely time to put down the tools and call a certified technician. Let’s get your hot water back on track.

What Exactly is Navien Error Code 110 01?

Think of Error Code 110 01 as a critical safety alert. Your Navien tankless water heater is a high-efficiency gas appliance, and like any furnace or boiler, it needs to vent combustion byproducts—like carbon monoxide—safely out of your home.

To do this, it uses a sophisticated system of sensors, including a pressure switch, to monitor airflow through the exhaust pipe. When the unit displays error 110 01, it means these sensors have detected abnormally high backpressure in the exhaust system.

In simpler terms, something is blocking the exhaust gases from escaping. The unit’s brain (the control board) immediately shuts down operation. This isn’t a malfunction; it’s a feature designed to prevent dangerous flue gases from backing up into your living space. It’s a vital part of what makes your system safe.

Common Causes of an External Exhaust Blockage Error

Before you panic, know that the cause behind a navien tankless water heater external exhaust blockage error 110 01 is often surprisingly simple and located right outside your home. Here are the most common culprits we see in the field. This section serves as a great starting point for understanding common problems with navien tankless water heater external exhaust blockage error 110 01.

Natural Debris and Nests

Your warm exhaust vent can seem like a five-star hotel for critters. Birds, wasps, squirrels, and other small animals often find the vent termination a perfect spot to build a nest.

In the fall, windblown leaves, twigs, and even plastic bags can get lodged inside the vent cap, creating a significant blockage.

Snow, Ice, and Weather-Related Blockages

Winter is a prime time for this error code. Heavy snowfall can completely bury a low-to-the-ground vent termination. Drifting snow can pack against it, and melting-and-refreezing cycles can create a solid cap of ice over the opening.

Even in warmer weather, fast-growing bushes, vines, or tall grass can obstruct the vent if not trimmed back regularly.

Improper Vent Installation or Termination

Sometimes, the problem dates back to the initial installation. High-efficiency venting has strict requirements. If the exhaust pipe doesn’t have the correct upward slope, condensation can pool and create a blockage or freeze in winter.

Other installation issues include a termination cap that is too close to a wall, soffit, or deck, which can cause exhaust gases to recirculate and trigger the pressure sensor.

Your Step-by-Step Guide to Safely Inspecting the Exhaust Vent

Ready to do a little detective work? This simple inspection can often solve the problem in minutes. But first, a critical safety warning.

SAFETY FIRST: Before you touch any part of your water heater or venting, you must turn off all electrical power to the unit. Locate the circuit breaker labeled “Water Heater” or a nearby emergency shut-off switch and turn it off. This prevents the unit from trying to fire up while you are inspecting it.

Power Down the Unit: We can’t stress this enough. Go to your home’s electrical panel and flip the breaker for your Navien unit to the “OFF” position. Confirm the display on the unit is blank.
Locate Your Vents: Go outside and find where your water heater vents. You will typically see two plastic (PVC) pipes coming out of the side of your house, often near the unit’s indoor location. One is the intake (for fresh air), and the other is the exhaust.
Perform a Visual Inspection: From a safe and stable position on the ground, look closely at the termination caps on the ends of the pipes. Do you see a bird’s nest, a clump of leaves, or a hornet’s nest inside? Is there a plastic bag caught on it?
Carefully Clear Obvious Debris: If you can safely reach the vent, put on a pair of gloves and carefully remove any visible blockages. Use a small brush or a shop vac (on blow or suction) to gently clear out any remaining debris.
Check for Snow and Ice: If it’s winter, check for snowdrifts or ice buildup. Gently clear away any snow and carefully chip away any ice that might be covering the opening. Never pour hot water on a frozen pipe, as it can crack the PVC.
Inspect the Intake Vent, Too: While you’re there, check the second pipe—the air intake. A blockage here can also cause pressure problems, so make sure it’s just as clear as the exhaust.
Power Up and Reset: Once you are confident the vents are clear, go back inside and turn the circuit breaker back on. The Navien unit should power up. You may need to press the reset button on the front panel to clear the error code from its memory.

How to Troubleshoot the Navien Tankless Water Heater External Exhaust Blockage Error 110 01

If you’ve cleared an obvious blockage and the unit is working, congratulations! But what if the error code comes right back? Here’s how to approach the next steps in this troubleshooting guide.

What If the Error Code Returns?

A persistent error code after you’ve cleared the external vent is a strong signal that the problem lies elsewhere. The blockage may be further down the pipe, or the issue may not be a blockage at all.

Potential internal culprits include:

A Sagging Vent Pipe: Over time, internal vent pipes can sag, creating a low spot where condensation pools and forms a water blockage.
A Faulty Pressure Switch: The very sensor that detects the blockage could be malfunctioning, sending a false signal to the control board.
A Failing Fan Motor: The induction draft motor that pushes exhaust gases out might be failing, unable to generate enough force to overcome the normal resistance of the vent pipe.

These issues are internal to the unit or the venting system and require professional tools and expertise to diagnose and repair safely.

The Benefits of Proper Venting: More Than Just Avoiding Errors

Maintaining clear venting isn’t just about fixing an error code; it’s about ensuring the health, safety, and efficiency of your water heater. Understanding the benefits of a clear exhaust path is key to long-term performance and is one of the most important navien tankless water heater external exhaust blockage error 110 01 best practices.

Enhanced Safety

This is the most critical benefit. Clear venting ensures that all combustion byproducts, including lethal carbon monoxide, are safely expelled from your home. An unobstructed vent is your family’s first line of defense.

Improved Efficiency and Longevity

Your Navien unit is engineered for high efficiency. When it can “breathe” easily, it operates exactly as designed, using the minimum amount of fuel to heat your water. This not only saves you money on utility bills but also reduces wear and tear on critical components like the fan motor and gas valve, extending the life of your investment.

Sustainable and Eco-Friendly Performance

An efficient water heater is an eco-friendly water heater. By ensuring the venting is clear, you promote complete combustion and optimal fuel use. This sustainable approach means your unit consumes less natural gas and produces fewer emissions, reducing your home’s carbon footprint. This is a core part of any good eco-friendly navien tankless water heater external exhaust blockage error 110 01 care plan.

When to Call a Professional HVAC Technician

While a DIY inspection is a great first step, knowing your limits is crucial for safety. It’s time to call a licensed and insured HVAC professional if you encounter any of the following situations:

The error code 110 01 returns after you’ve thoroughly cleared the external vent terminations.
The vents are located on a high roof or are otherwise inaccessible or unsafe for you to reach.
You hear rattling, grinding, or other unusual noises coming from the unit, which could indicate a failing fan.
You are not comfortable performing any of the inspection steps. Your safety is always the top priority.
You smell gas. If you ever smell a “rotten egg” odor near your unit, leave the house immediately, do not use any electronics or light switches, and call your gas company’s emergency line from a safe distance.

A qualified technician has specialized tools, like a manometer to test gas and vent pressures, and the expertise to safely disassemble venting, inspect internal components, and ensure your system is operating according to manufacturer specifications.

Frequently Asked Questions About Navien Error 110 01

Can I just keep resetting my Navien water heater if I get error 110 01?

Absolutely not. The error code is a safety lockout for a reason. Continuously resetting the unit without addressing the underlying blockage can put you at risk of carbon monoxide exposure and can cause damage to the water heater’s internal components.

How can I prevent exhaust blockages in the future?

Prevention is the best medicine! Make it a habit to visually inspect your vent terminations a few times a year, especially in the fall when leaves are flying and after major snowstorms. Trim back any encroaching bushes or plants. For extra protection, you can ask a technician to install an approved vent screen or guard, which can help keep critters out. This is a key part of our navien tankless water heater external exhaust blockage error 110 01 care guide.

Is error 110 01 the same as other Navien error codes?

No. Navien uses a wide range of error codes to pinpoint specific issues. For example, an error code 10E points to an air pressure sensor issue, while a 27E indicates a problem with the heat exchanger. Error 110 01 is specifically related to the detection of high backpressure in the exhaust system.

How much does it cost to fix an exhaust blockage?

The cost can vary dramatically. If the fix is simply clearing a bird’s nest from the termination cap, you may only pay for a basic service call fee. However, if the problem requires disassembling the vent pipe to clear an internal blockage or replacing a faulty fan motor, the cost will be higher, involving both labor and parts.

Tackling a navien tankless water heater external exhaust blockage error 110 01 can feel intimidating, but in many cases, the solution is within reach for a safety-conscious homeowner. By understanding what the error means and following a safe inspection process, you can often restore your hot water yourself.

Remember to always prioritize safety by shutting off the power first, and never hesitate to call a trusted professional when the problem is beyond a simple external blockage. A well-maintained Navien unit is a safe, efficient, and reliable source of endless hot water.

Stay safe and stay comfortable!

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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.