Navien Tankless Water Heater 44E Error Code - Decoding And Fixing Low

That sinking feeling when you turn on the shower and get a blast of cold water is bad enough. But when you check your unit and see a cryptic “navien tankless water heater 44e error code” flashing on the display, it can feel downright intimidating. You just want hot water, not a puzzle to solve.

But don’t worry. As an HVACR technician with years of field experience, I can tell you this is one of the most common issues we see, and it’s often something you can troubleshoot and fix yourself in under an hour. This isn’t a catastrophic failure; it’s your water heater’s way of telling you something is restricting its flow.

I promise to walk you through exactly what this code means, the safe steps you can take to diagnose the problem, and how to get your hot water flowing again. Imagine having steady, reliable hot water without the stress of an unexpected service call.

In this complete navien tankless water heater 44e error code guide, we’ll break down the causes, provide a step-by-step checklist, and share the best practices to keep this error from coming back. Let’s get started.

What Does the Navien 44E Error Code Actually Mean?

First things first, let’s demystify that code. The Navien 44E error code means one thing: Low Water Flow Detected.

Inside your tankless water heater is a sophisticated flow sensor. Its job is to measure how much water is moving through the unit. If the flow rate drops below a certain minimum (usually around 0.5 gallons per minute), the sensor tells the main control board to shut down the burner.

This is a crucial safety feature. Firing up the powerful heat exchanger without enough water moving through it could cause it to overheat, flash-boil the water inside, and potentially damage the unit permanently. So, while it’s an annoyance, the 44E error is your Navien protecting itself from serious harm.

Uncovering the Root Causes: Common Problems with the Navien 44E Error

Now that you know the “what,” let’s explore the “why.” The low water flow condition is almost always caused by a blockage somewhere in your system. Think of it like a clogged artery in your home’s plumbing. Here are the most common culprits, starting with the easiest to check.

Clogged Inlet Water Filter

This is the number one cause of the 44E error, bar none. Your Navien has a small screen filter on the cold water inlet pipe to catch sediment, debris, and mineral scale before it enters the unit. Over time, this filter does its job so well that it gets clogged, severely restricting water flow.

Blocked Fixture Aerators or Showerheads

Sometimes the problem isn’t at the water heater at all! The tiny screens on your faucet aerators and showerheads can get clogged with the same mineral deposits. If the blockage is bad enough, not enough water can flow through to trigger the Navien’s flow sensor, resulting in the error.

A Malfunctioning Flow Sensor

While less common, the flow sensor itself can fail. It might get stuck due to scale buildup or simply wear out over time. If the sensor can’t properly detect the water flow, it will mistakenly report a low-flow condition and trigger the 44E error, even if the water pressure is fine.

Partially Closed Water Valves

It sounds simple, but it happens more than you’d think. The main shut-off valve to the water heater or even your home’s main water valve might have been partially closed during other work and never fully reopened. This will directly limit the flow available to the unit.

Internal Limescale Buildup (Scaling)

If you live in an area with hard water, this is a major long-term concern. Over years, limescale can build up inside the narrow pipes and channels of the heat exchanger, slowly choking off water flow. This is a more serious issue that requires a specific cleaning procedure called descaling.

Your Step-by-Step Guide: How to Fix the Navien Tankless Water Heater 44E Error Code

Alright, let’s roll up our sleeves. We’re going to walk through a few safe checks together. Follow these steps in order, as they go from the simplest fix to the more involved.

Safety First: Before you begin, unplug your Navien water heater or turn off the circuit breaker that powers it. You should also turn off the cold water supply valve leading to the unit.

Step 1: Check Your Faucet Aerators
Start with the easiest possible fix. Go to the faucet where you first noticed the lack of hot water. Unscrew the very tip of the faucet (the aerator). You may need pliers with a rag to avoid scratching the finish. Check the small screen inside for grit or buildup. Clean it out, reassemble, and test again. Do the same for your showerhead if that’s where the issue occurs.
Step 2: Inspect and Clean the Inlet Water Filter
This is the most likely solution. With the power and water off, locate the cold water inlet pipe on the bottom of your Navien (it’s usually the right-most pipe). You’ll see a small, round cap or plug—this is the filter housing. Place a small bucket underneath to catch any residual water.
Unscrew the cap (you may need channel-lock pliers). The small, thimble-shaped screen filter will come out with it. Gently clean this screen with an old toothbrush under running water until it’s completely clear of debris. Do not use a wire brush, as it can damage the screen. Once clean, carefully re-insert the filter and tighten the cap snugly.
Step 3: Verify All Water Valves Are Fully Open
Trace the water lines back from your unit. Ensure the handle on the cold water inlet valve is parallel to the pipe, indicating it’s fully open. If you have one, also check the main water shut-off for your house to be sure it’s completely open.
Step 4: Reset the Unit
Once you’ve cleaned the filters and checked the valves, it’s time to restore power. Turn the water supply valve back on slowly. Then, plug the unit back in or flip the circuit breaker on. The unit will go through its startup cycle. The error code should be gone.
Step 5: Test the System
Go to a faucet and turn on the hot water. It may take 30-60 seconds for the hot water to arrive, but you should hear the Navien fire up and see the temperature begin to rise on its display. If the hot water flows steadily and the error code doesn’t return, you’ve successfully solved the problem!

When to Put Down the Tools and Call a Professional

While the DIY approach works for most 44E errors, there are times when you absolutely need a licensed and insured technician. Your safety and the health of your equipment are the top priorities.

The Error Immediately Returns: If you’ve cleaned the inlet filter and aerators and the 44E code comes right back, the issue is likely internal, such as a failed flow sensor.
You Suspect Heavy Scale Buildup: If your water is very hard and the unit hasn’t been serviced in over a year, the problem may be internal scaling. Descaling involves pumping a special chemical solution through the unit and is best left to a pro.
You See Any Leaks: If you notice any dripping or water pooling around the unit after your work, shut off the water and power immediately and call for service.
You’re Not Comfortable: If at any point you feel unsure or uncomfortable with the steps, there is no shame in calling a professional. It’s always better to be safe.

Best Practices for Preventing the 44E Error Code

Fixing a problem is great, but preventing it is even better. Adopting a simple navien tankless water heater 44e error code care guide will ensure reliability and efficiency for years to come. These are the best practices we recommend to all our clients.

Regularly Clean Your Filters

Mark your calendar! Make a habit of cleaning the main inlet water filter and your most-used faucet aerators every 4-6 months. This simple, 15-minute task is the single best thing you can do to prevent the 44E error.

Schedule Annual Professional Maintenance

Have a qualified technician service your Navien unit once a year. This service should include a full inspection, cleaning, and, most importantly, descaling the heat exchanger. This not only prevents flow errors but also maintains the unit’s energy efficiency, making it a more sustainable and eco-friendly choice in the long run.

Consider a Whole-Home Water Softener

If you live in an area with hard water, the ultimate long-term solution is a water softener. By removing the minerals that cause scale *before* they ever reach your water heater, you protect your investment, improve performance, and drastically reduce the need for frequent descaling.

Frequently Asked Questions About the Navien 44E Error Code

How much does it cost to fix a Navien 44e error?

The cost can vary greatly. If it’s a clogged filter you clean yourself, the cost is $0. If you need a professional to come out, you can expect a service call fee of around $150-$250, which usually covers cleaning the filter. If parts like the flow sensor need to be replaced, the total cost could be closer to $300-$500.

Can I just ignore the 44e error code?

No. The 44e error code is a functional lockout. Your Navien unit will not produce any hot water while this error is active. It’s a safety mechanism that must be addressed by restoring proper water flow before the unit will operate again.

Is cleaning the Navien inlet filter difficult?

For most DIY-capable homeowners, it is not a difficult task. As long as you remember to turn off the power and water first and have a pair of pliers and a small brush, it’s a very straightforward process. Our step-by-step guide above covers everything you need to know.

Does hard water cause the 44e error code?

Yes, absolutely. Hard water is a primary contributor to the common problems with navien tankless water heater 44e error code. The minerals in hard water create limescale, which is the “gunk” that clogs the inlet filter, fixture aerators, and can eventually choke the heat exchanger itself, leading directly to this low-flow error.

Tackling an error code on a sophisticated piece of equipment like a Navien tankless water heater can feel daunting, but you are now equipped with the expert knowledge to diagnose and handle the most common cause.

By following this guide, you’ve learned not just how to fix the immediate problem but also how to implement the navien tankless water heater 44e error code best practices to keep your system running smoothly. Regular maintenance is key to enjoying the efficiency and endless hot water your Navien was designed to provide.

Stay safe, stay comfortable, and enjoy that reliable hot water!

Author
Recent Posts

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.