Navien Water Heater Not Working Leaking Water - A Pro'S Step-By-Step

There’s nothing more jarring than expecting a hot shower and getting an icy blast instead. But the real alarm bells go off when you discover a puddle forming under your unit. A navien water heater not working leaking water is a two-pronged problem that can feel overwhelming, but don’t worry—you’ve come to the right place.

We understand that feeling of panic. As HVACR technicians, we’ve helped countless homeowners navigate this exact situation. The good news is that you have the power to safely assess the problem and take the right first steps.

This comprehensive guide promises to be your trusted resource. We’ll walk you through immediate safety protocols, help you identify the source of the leak, troubleshoot the “no hot water” issue, and give you the confidence to know when a DIY check is safe and when it’s time to call for professional backup.

Let’s get your hot water back on and that leak stopped, safely and efficiently.

Safety First: Your Immediate Action Plan for a Leaking Water Heater

Before you even think about troubleshooting, your top priority is to contain the situation and ensure your home is safe. Water and electricity (or gas) are a dangerous mix. Follow these steps immediately.

Shut Off the Power: Go to your home’s electrical panel and find the breaker dedicated to your tankless water heater. Flip it to the “OFF” position. If you have a plug-in model, unplug it from the wall, but only if the area is completely dry.
Turn Off the Gas Supply: Locate the gas shut-off valve on the gas line leading to your Navien unit. It usually has a yellow or red handle. Turn the handle a quarter-turn so it is perpendicular (at a 90-degree angle) to the pipe. This stops the flow of gas.
Stop the Water Flow: Find the cold water inlet valve for your water heater. It’s typically a blue-handled lever or a round knob. Turn it clockwise until it stops to shut off the water supply to the unit. This will prevent more water from feeding the leak.

Once you’ve secured the power, gas, and water, you can breathe a little easier. You’ve successfully prevented a minor issue from escalating into a major hazard or catastrophic water damage. Now, we can move on to diagnosis.

Diagnosing the Drip: Pinpointing the Source of the Leak

Not all leaks are created equal. Finding where the water is coming from is the most critical clue in understanding the severity of the problem. Grab a flashlight and carefully inspect your unit. The source of the leak often points directly to the solution.

H3: Leaking from Water Connection Fittings

This is one of the most common and, thankfully, often simplest issues to fix. Check the hot and cold water lines where they connect to the bottom of the Navien unit.

The Cause: Over time, the threaded connections or the rubber gaskets inside them can loosen or degrade, causing a slow drip. This is especially common after the initial installation if the fittings weren’t tightened sufficiently.
What to Do: With the water turned off, you can use two wrenches (one to hold the unit’s fitting, one to turn the connector) to gently tighten the connection. Do not overtighten, as this can crack the fitting. If the leak persists, the gasket inside likely needs to be replaced—a job best left to a plumber or technician.

H3: Dripping from the Pressure Relief Valve (PRV)

The Temperature and Pressure Relief (TPR or PRV) valve is a crucial safety device. It’s designed to release water if the pressure or temperature inside the unit gets too high. A small, occasional drip might be normal, but a steady stream is a red flag.

The Cause: The leak could be caused by excessive pressure in your home’s plumbing system, a failing expansion tank, or a faulty PRV itself. Sometimes, sediment can get caught in the valve, preventing it from sealing properly.
What to Do: This is a symptom of a larger problem. While you could try briefly opening and closing the valve to flush debris, a constantly leaking PRV requires a professional diagnosis. A technician needs to test your home’s water pressure and inspect the system to find the root cause.

H3: Condensate Line Issues

Navien units are high-efficiency condensing heaters. This means they produce acidic condensation as a byproduct of heating. This water is safely drained away through a plastic (PVC or other approved material) pipe.

The Cause: If this line becomes clogged with debris or algae, or if it freezes in the winter, the water will back up and leak out of the unit’s casing or a nearby joint.
What to Do: You can often clear a simple clog yourself. Check where the condensate line terminates (often outside or into a floor drain) and ensure it’s clear. You can also disconnect the line from the unit (consult your manual) and gently blow through it or use a wet/dry vac to pull the clog out. This is a key part of any good navien water heater not working leaking water care guide.

No Hot Water? Common Problems with Navien Water Heater Not Working Leaking Water

Now let’s tackle the second half of the problem: the lack of hot water. Sometimes the leak is directly related to the failure, and other times they are two separate issues. Here’s a breakdown of the common problems with a navien water heater not working leaking water.

H3: Internal Component Leak Causing a Shutdown

This is the most serious scenario. If the leak is coming from inside the main casing of the unit and dripping out from the bottom, it likely means a critical component has failed.

The Cause: The heat exchanger, a primary component, can develop cracks or pinhole leaks due to scale buildup (from hard water) or age. Other internal O-rings, seals, or manifolds could also be the culprit.
The Result: Navien units have internal leak sensors. If water is detected inside the cabinet, the system will shut down as a safety precaution, preventing it from firing up and giving you hot water. This is why a leak and a “no hot water” situation often happen simultaneously.
What to Do: An internal leak is not a DIY repair. It requires disassembly of the unit and specialized parts. This is a firm “call a pro” situation.

H3: Flow Sensor Malfunction

The flow sensor is the part that tells your Navien unit, “Hey, someone turned on a hot water tap! Time to fire up!” If this sensor is faulty or clogged with mineral scale, it won’t send the signal.

The Cause: Hard water is the number one enemy of flow sensors. Tiny mineral deposits can impede its function. While less common, the sensor can also fail electronically.
What to Do: Regular descaling (flushing the unit with a vinegar or approved solution) is the best preventative measure. A technician can clean or replace a faulty flow sensor relatively easily. This is a core part of the navien water heater not working leaking water best practices for maintenance.

H3: Ignition Failure

You might hear the unit click or the fan start, but it never actually ignites to heat the water. This can be frustrating and points to a problem in the ignition sequence.

The Cause: Common culprits include a dirty flame sensor, a blocked igniter, a faulty gas valve, or issues with the air intake or exhaust vents being blocked by debris, nests, or snow.
What to Do: You can perform a quick visual inspection of the exterior vent pipes to ensure they are clear. However, troubleshooting the internal ignition system involves working with gas and high-voltage components and should only be handled by a qualified technician.

DIY Checks vs. Calling a Pro: Knowing Your Limits

As an empowered homeowner, it’s great to understand your system. But knowing where to draw the line between a simple check and a dangerous repair is crucial. Here is a clear guide.

H3: Safe DIY Checks You Can Perform

Check the Display Panel: Look for any error codes. Your Navien manual will have a list of codes and what they mean. This gives you (and your technician) a huge head start.
Inspect External Pipes: Check the condensate drain line for clogs and the water connections for drips.
Verify Venting is Clear: Make sure the intake and exhaust pipes on the exterior of your home are not blocked by leaves, snow, or animal nests.
Reset the Unit: After you’ve resolved a simple issue (like a blocked vent), you can try restoring power and resetting the unit. If the problem persists, shut it down again.

H3: When to Immediately Call a Certified Navien Technician

If You Smell Gas: Shut off the gas immediately, evacuate the area, and call your gas company and an HVAC professional from a safe location.
For Any Internal Leaks: If water is coming from inside the main cabinet, it’s a sign of a major component failure.
Persistent Error Codes: If a reset doesn’t clear an error code, it points to a hardware or sensor failure that needs professional service.
Disassembling the Unit: Never open the main casing of your tankless water heater. This exposes you to gas lines and electrical components and will void your warranty.

Preventative Maintenance: Your Navien Water Heater Care Guide

The absolute best way to handle a navien water heater not working leaking water is to prevent it from ever happening. Consistent maintenance is key to a long, efficient life for your unit.

Adopting these sustainable navien water heater not working leaking water practices not only saves you money on repairs but is also an eco-friendly approach, as it extends the lifespan of your appliance and keeps it running at peak efficiency.

Annual Descaling/Flushing: This is the single most important maintenance task. If you have hard water, mineral scale builds up inside the heat exchanger, reducing efficiency and eventually causing leaks and failures. Flushing the unit with a descaling solution removes this buildup.
Clean the Inlet Water Filter: Your Navien has a small filter on the cold water inlet to catch sediment. Cleaning this every 6-12 months prevents debris from entering the unit and damaging sensitive components like the flow sensor.
Inspect Vents and Condensate Line: Seasonally, make sure your intake/exhaust vents are clear and that the condensate line is draining freely.

Frequently Asked Questions About Navien Water Heater Problems

Why is my Navien water heater leaking from the bottom?

A leak from the bottom of the main cabinet is often a serious issue. It could be a cracked heat exchanger (due to scale buildup), a failed internal seal, or a backed-up condensate drain. The first two require professional repair, while the last one might be a simple clog you can check yourself.

What does a Navien error code E012 mean?

Error code E012 typically indicates a flame loss, meaning the unit ignited but the flame went out. This can be caused by improper gas pressure, a dirty flame sensor, or an issue with the venting. It’s a common problem that requires a technician to diagnose accurately.

How long should a Navien tankless water heater last?

With proper and consistent maintenance, including annual descaling, a Navien tankless water heater can last 15 to 20 years or even longer. Neglecting maintenance, especially in areas with hard water, can significantly shorten its lifespan.

Can I fix a leaking Navien water heater myself?

You can safely fix leaks from external water connection fittings by gently tightening them. You can also clear a clogged condensate drain line. However, any leaks from the pressure relief valve or from inside the unit’s main body should be handled by a licensed and insured professional.

Dealing with a broken and leaking water heater is stressful, but by following this guide, you’ve taken the most important steps toward a safe and effective solution. You’ve secured the area, performed a basic diagnosis, and now understand the path forward.

Remember, your Navien unit is a sophisticated piece of equipment. Investing in professional maintenance and timely repairs is the best way to ensure you have reliable, efficient hot water for years to come. Stay safe, and don’t hesitate to call for help when you need it!

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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.