Navien Water Heater E351 – Your Complete Troubleshooting & Fix Guide
That sinking feeling when you step into the shower expecting a rush of hot water, only to be met with a lukewarm trickle… it’s a frustrating start to any day. You check your Navien tankless water heater, and a cryptic error code is staring back at you: E351. We get it. Seeing an error code can feel intimidating, and your mind immediately jumps to expensive repairs.
But here’s the good news. We promise to walk you through exactly what this error means and how to handle it. Many of the common causes are surprisingly simple to identify and even fix yourself, safely.
In this complete navien water heater e351 guide, we’ll break down the common culprits, provide a step-by-step troubleshooting checklist you can follow, and help you understand when it’s time to call in a trusted professional. Let’s get that hot water flowing again!
What Exactly is the Navien Water Heater E351 Error Code?
Think of error codes as your water heater’s way of communicating. They aren’t just random numbers; they point to a specific problem. The navien water heater e351 error code specifically signals an issue with the air pressure sensor.
So, what does that sensor do? In your high-efficiency Navien unit, proper airflow is critical for safe and efficient operation. The air pressure sensor is a safety device that constantly monitors the pressure within the vent system.
If it detects that the pressure is too high or too low, it tells the main control board to shut the unit down to prevent unsafe combustion. It’s a crucial feature that ensures exhaust gases are being vented properly and your system is breathing correctly.
Common Problems with Navien Water Heater E351 You Can Investigate
Before you panic, let’s explore the most frequent reasons this error appears. More often than not, the problem isn’t a catastrophic failure but a simple obstruction. This is where you can start your investigation.
Blocked Venting or Intake Pipes
This is, by far, the most common culprit. Your Navien unit has two pipes leading outside: one for drawing in fresh air for combustion (intake) and one for pushing out exhaust gases (exhaust). If either of these gets blocked, the air pressure sensor will do its job and shut the system down.
Common blockages include:
- Leaves, twigs, and other yard debris
- Snow and ice buildup during winter
- Bird or rodent nests built inside the pipe opening
- Insect nests or webs
Condensate Drain Issues
High-efficiency water heaters like Navien produce condensation as a byproduct of their process. This water is drained away through a small plastic tube, usually at the bottom of the unit. If this condensate line becomes clogged or freezes, water can back up into the unit, affecting the internal pressure and tripping the E351 sensor.
A Faulty Air Pressure Sensor or Tubing
Sometimes, the component itself is the problem. The small rubber or silicone tube connecting the sensor to the vent system can become cracked, brittle, or disconnected. In other cases, the electronic sensor itself may have simply failed after years of service.
Loose Wiring or Connections
It might sound too simple, but a loose wire connecting the air pressure sensor to the main control board can easily cause an intermittent or persistent E351 error. Vibrations from the unit’s normal operation can sometimes be enough to wiggle a connection loose over time.
Your Step-by-Step DIY Troubleshooting Guide for Navien Water Heater E351
Ready to do some detective work? Don’t worry—we’ll walk through a few safe checks together. These steps can help you solve the problem without even picking up a tool.
Important Safety Warning: Before you touch or open any part of your water heater, you MUST turn off the electrical power to the unit at your breaker panel. For gas units, it’s also wise to shut off the gas supply valve leading to the heater.
Inspect the Exterior Vents: Go outside to where your water heater’s intake and exhaust pipes terminate. Carefully check the openings for any of the blockages we mentioned—leaves, snow, nests, etc. Clear away any debris you find. This simple step resolves a huge percentage of E351 errors.
Check the Condensate Line: Locate the clear or white plastic tube at the bottom of your Navien unit. Follow it to where it drains. Ensure it’s not kinked, clogged, or, if it’s cold outside, frozen solid. If it’s clogged, you may be able to gently clear it. If it’s frozen, a hairdryer on a low setting can help thaw it safely.
Power Cycle the Unit (The “Reboot”): This is the classic “turn it off and on again” trick. Go to your electrical panel and flip the breaker for your water heater to the OFF position. Wait a full five minutes. This allows the internal electronics to fully reset. Then, flip the breaker back ON. Sometimes, this is all it takes to clear a temporary sensor fault.
A Quick Internal Check (For the Confident DIYer): If you are comfortable and have turned off the power, you can remove the front cover of your Navien unit (usually held by a few screws). Look for a small, squarish component with a thin tube and a few wires attached—this is the air pressure sensor. Gently check that the tube is securely attached at both ends and isn’t cracked or filled with water. Ensure the electrical connector is pushed firmly into place. Do not force anything. If it looks loose, secure it and see if the error clears after restoring power.
When to Put Down the Tools and Call a Professional
While DIY checks are great for simple issues, your safety is the top priority. Tankless water heaters are complex appliances that combine gas, water, and high-voltage electricity. Here’s when it’s absolutely time to call a licensed and certified Navien technician.
- If the E351 error code returns immediately after you’ve cleared the vents and reset the unit.
- If you are not 100% comfortable opening the unit’s access panel.
- If you suspect the sensor itself, the main control board, or the combustion fan motor is faulty.
- If you see any signs of water leakage, soot, or melting plastic inside the unit.
A professional has the diagnostic tools and replacement parts to accurately test the sensor and other components, ensuring the repair is done correctly and safely.
Navien Water Heater E351 Best Practices: How to Prevent This Error
The best way to deal with an error code is to prevent it from happening in the first place. Following a good navien water heater e351 care guide can save you headaches and money. These are the best practices we recommend to all homeowners.
Perform Regular Vent Inspections
Make it a habit to visually inspect your exterior vent pipes every season. Clear away growing shrubs, pull out any visible debris, and make sure they are unobstructed, especially after a storm or heavy snowfall.
Schedule Annual Professional Maintenance
This is the single most important tip. An annual service call from a qualified technician is invaluable. They will thoroughly clean the unit, inspect all sensors and safety devices, flush the condensate line, and ensure your system is running at peak efficiency. This proactive care is the key to longevity and reliability.
Keep the Surrounding Area Clear
Ensure the area immediately around your water heater is free of clutter, laundry, and stored items. This allows for proper airflow to the unit and gives technicians easy and safe access when service is needed.
The Sustainable Side: Eco-Friendly Benefits of a Healthy Navien Unit
Fixing an error like E351 isn’t just about getting your hot water back; it’s also about efficiency. A core benefit of a sustainable navien water heater e351-free system is its eco-friendly performance.
When your unit can “breathe” properly with clear vents, it achieves complete and efficient combustion. This means it uses the minimum amount of fuel necessary to heat your water, lowering your energy bills and reducing your carbon footprint.
Promptly addressing errors and sticking to a maintenance schedule ensures your eco-friendly navien water heater e351 system operates as designed, saving energy and protecting the environment one hot shower at a time.
Frequently Asked Questions About Navien Water Heater E351
Can I just reset my Navien water heater to clear the E351 code?
You can, and it’s a good first step! However, if the underlying problem (like a blocked vent) isn’t fixed, the error code will almost certainly reappear. Resetting is a temporary fix, not a permanent solution. The code is a symptom; you need to find the cause.
How much does it cost to fix a Navien E351 error?
The cost can vary dramatically. If the fix is simply clearing a blocked vent pipe that you do yourself, it costs nothing. A professional service call to clear a clog or flush a condensate line might cost between $100-$250. If a component like the air pressure sensor or fan motor needs replacement, the cost could range from $300-$600+, including parts and labor.
Is the E351 error dangerous?
The error code itself is a sign that a safety feature is working correctly by shutting the unit down. The potential danger comes from the cause of the error. For example, a blocked exhaust vent could lead to a buildup of carbon monoxide if the unit were to continue running. Therefore, you should never ignore this error and always address the root cause promptly.
Where is the air pressure sensor located on my Navien water heater?
Typically, the air pressure sensor is located in the upper portion of the unit, near the exhaust fan and venting connections. It will have a small-diameter tube running from it to the vent assembly and a wire harness connecting it to the main control board. For the exact location on your model, it’s always best to consult your owner’s manual.
Tackling an error code on your water heater can feel daunting, but you’ve already taken the most important step by seeking out information. Remember to start with the simple, safe checks, and never hesitate to call a professional if you’re unsure. A little knowledge and proactive care go a long way in keeping your home’s systems running smoothly.
You’ve got this! Stay safe, and enjoy that reliable hot water.
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