How To Ignite Navien Tankless Water Heater: Your Complete DIY

Stepping into a shower expecting a blast of hot water, only to be met with an icy shock, is one of life’s less pleasant surprises. When you check your Navien tankless unit and see it isn’t running, your first thought is probably, “How do I get this thing fired up again?”

You’ve come to the right place. As an experienced HVACR technician, I can promise you that understanding how to ignite Navien tankless water heater units is often much simpler than you think. Unlike old-school water heaters, there’s no pilot light to fuss with. The process is automatic, but it relies on a few key things being in order.

In this complete guide, we’ll walk through exactly how Navien’s ignition works, what to do after a power outage or gas shut-off, and how to safely troubleshoot the most common ignition failures. Imagine having the confidence to solve the problem yourself and get that glorious, endless hot water flowing again. Let’s get started.

Understanding Navien’s Automatic Ignition System: Why There’s No Pilot Light

First things first, let’s clear up a common misconception. If you’re searching for a pilot light on your Navien unit, you won’t find one. Modern, high-efficiency units like Navien use a direct electronic ignition system for safety and energy savings.

This is one of the key benefits of how to ignite Navien tankless water heater systems—they only use gas when you actually need hot water. There’s no tiny flame constantly burning, wasting fuel day and night.

Here’s how it works in a nutshell:

You Turn On a Hot Water Tap: This is the trigger. A flow sensor inside the unit detects the movement of water.
The Brains Kick In: The flow sensor sends a signal to the main control board (the unit’s computer).
The Safety Sequence Begins: The control board starts the exhaust fan to ensure the venting is clear. It then opens the gas valve.
Sparks Fly: An electronic igniter creates a high-voltage spark to light the gas flowing into the burner. A flame sensor confirms a stable flame has been established.
You Get Hot Water: The burner heats the water passing through the heat exchanger, and you get on-demand hot water at your faucet.

This entire process happens in seconds. When the unit fails to ignite, it means there’s a problem somewhere in this sequence. Our job is to figure out where.

The Step-by-Step Guide: How to Ignite Navien Tankless Water Heater After a Reset

Whether you’ve had a power outage, the gas was turned off for maintenance, or the unit displayed an error code, the “re-ignition” process is essentially a guided reset. Think of it less as lighting a flame and more as ensuring the system has everything it needs to light itself.

Follow this how to ignite navien tankless water heater guide carefully. We’ll walk through it together.

Step 1: A Quick Safety Check

Before touching anything, use your nose. Do you smell gas around the unit? If you detect a faint or strong “rotten egg” smell, stop immediately. Do not touch any electrical switches. Leave the area, and call your gas company’s emergency line from a safe distance.

Step 2: Confirm Electrical Power

Your Navien is smart, but it can’t do anything without electricity. The control board, fan, and igniter all need power.

Check the Plug: Make sure the unit is securely plugged into its power outlet.
Test the Outlet: Is the outlet a GFCI (the kind with “Test” and “Reset” buttons)? If so, press the “Reset” button firmly. To be sure the outlet has power, unplug the water heater and plug in a small lamp or phone charger to test it.
Check the Breaker: Go to your home’s main electrical panel. Find the circuit breaker labeled “Water Heater” or similar. If it’s tripped (in the middle or “Off” position), flip it firmly to “Off” and then back to “On.”

Step 3: Verify the Gas Supply is On

No gas means no flame. It’s a common oversight, especially if other work has been done in the house.

Find the gas shut-off valve on the pipe leading to your Navien unit. The valve handle should be parallel to the gas pipe, indicating it’s open.
If the handle is perpendicular (forming a “T” with the pipe), it’s closed. Turn it so it’s parallel to the pipe.
If you’re unsure, check another gas appliance in your home, like a stove or furnace, to confirm the main gas supply is on.

Step 4: Power Cycle (Reset) the Unit

This is the classic “turn it off and on again” trick, and it works wonders for electronics, including your water heater’s control board.

Simply unplug the Navien unit from the wall outlet. Wait for at least 30-60 seconds. This gives the internal capacitors time to fully discharge and clears any temporary glitches from the control board’s memory. Then, plug it back in securely.

Step 5: Initiate a Call for Hot Water

Now it’s time to tell the unit you want it to work. Go to a faucet—the one closest to the water heater is often best—and turn the hot water on full blast. This strong flow ensures the flow sensor is properly triggered.

Step 6: Listen and Observe

Stand near the unit (safely) and listen. You should hear a sequence of sounds:

The whir of the exhaust fan starting up.
A series of distinct clicks as the electronic igniter sparks.
A soft “whoosh” as the main burner ignites.

If all goes well, the unit’s display will show the temperature rising, and you’ll have hot water at your tap within a minute. Congratulations, you’ve successfully prompted the ignition!

Common Problems with How to Ignite Navien Tankless Water Heater (And How to Fix Them)

If you’ve followed the steps above and still have no hot water, don’t panic. The unit is likely protecting itself and telling you where the problem is. Here are some of the most common issues we see in the field.

Problem: Blocked Air Intake or Exhaust Venting

Your Navien needs to breathe. It pulls in fresh air for combustion and pushes out exhaust fumes. If either of these pathways is blocked, a pressure sensor will prevent the unit from firing for safety.

What to Look For: Check the PVC vent pipes on the outside of your house. Are they blocked by snow, leaves, bird nests, or debris?
The Fix: Carefully clear away any visible obstructions from the vent terminals. Never stick anything deep inside the pipes. If you suspect an internal blockage, it’s time to call a pro.

Problem: Clogged Condensate Drain

High-efficiency condensing units like Navien produce acidic water (condensate) as a byproduct of combustion. This water must drain away freely. If the drain line gets clogged with sediment or freezes, a sensor will shut the unit down to prevent water damage.

What to Look For: You’ll see a small, clear or white plastic tube at the bottom of the unit. Check if it’s kinked, blocked, or, in winter, frozen solid.
The Fix: If you see a clog at the end of the tube, you may be able to clear it. If it’s frozen, you can try warming it gently with a hairdryer. Regular maintenance helps prevent this. This is a key part of any how to ignite navien tankless water heater care guide.

Problem: Low Gas Pressure

Sometimes, the issue isn’t a lack of gas, but not enough gas pressure to sustain a stable flame. This can be caused by an undersized gas line, a problem with the gas meter, or an issue with the utility provider.

What to Look For: The unit might try to light, you’ll hear the “whoosh,” but it immediately shuts off. It may repeat this cycle a few times before showing an error code.
The Fix: This is not a DIY job. Gas pressure must be measured and adjusted by a licensed technician with a manometer.

Problem: Dirty Flame Sensor or Faulty Igniter

Over time, the flame sensor rod can get coated with residue, preventing it from detecting the flame. Likewise, the igniter can weaken or fail. The control board thinks there’s no flame (even if there is one for a second) and shuts off the gas as a safety precaution.

What to Look For: The unit clicks repeatedly but never ignites, or it ignites for only 2-3 seconds before shutting down.
The Fix: While cleaning a flame sensor is a common task for a technician, it requires opening the unit’s combustion chamber. Due to the safety risks involved with gas appliances, we strongly recommend leaving this repair to a qualified professional.

Best Practices for Navien Ignition: A Care Guide for Long-Term Reliability

The best way to deal with ignition problems is to prevent them from happening in the first place. Following these how to ignite navien tankless water heater best practices will keep your unit running efficiently and reliably for years.

Perform Annual Flushing (Descaling)

If you live in an area with hard water, mineral scale (calcium and magnesium) will build up inside the heat exchanger. This buildup restricts water flow, forcing the unit to work harder and potentially damaging internal components like the flow sensor.

Flushing your unit annually with a descaling solution removes this buildup, maintains efficiency, and protects your investment. This is the single most important maintenance task for any tankless water heater.

Keep Vents Clear and Inspected

Make it a habit to visually inspect your exterior vent terminals every season. Trim back bushes, clear away leaves, and ensure nothing is built or stored in front of them. This simple check ensures your unit can always breathe properly.

Check the Condensate Line

A few times a year, just take a look at the condensate drain line. Make sure it’s not clogged or kinked and that water is flowing freely when the unit is running (especially during colder months when it produces more condensate).

The Eco-Friendly Advantage: Why On-Demand Ignition is a Sustainable Choice

Choosing a Navien tankless unit isn’t just about endless hot water; it’s also a smart, eco-friendly how to ignite navien tankless water heater choice. The on-demand electronic ignition system is at the heart of its efficiency.

By eliminating the pilot light, you’re not burning gas 24/7 just to keep a small flame alive. This alone can save a surprising amount on your utility bills and reduce your home’s carbon footprint. Furthermore, by only heating water when you need it, you eliminate the standby heat loss that plagues traditional tank-style heaters, which constantly reheat a large reservoir of water.

This sustainable how to ignite navien tankless water heater technology is better for your wallet and the planet.

Frequently Asked Questions About How to Ignite Navien Tankless Water Heater

Does my Navien have a pilot light I need to light manually?

No. Navien tankless water heaters do not have a standing pilot light. They use a safe and efficient direct electronic ignition system that only activates when you turn on a hot water tap.

What does it mean if my Navien keeps clicking but won’t light?

Repetitive clicking is the sound of the electronic igniter trying to spark. If it clicks but doesn’t ignite, the most common causes are an interrupted gas supply, a dirty or faulty flame sensor/igniter assembly, or low gas pressure. First, double-check that your gas valve is fully open. If that doesn’t solve it, it’s best to call a technician.

How do I reset my Navien water heater after an error code?

The simplest way to reset the unit is to power cycle it. Unplug the unit from the electrical outlet, wait a full minute, and then plug it back in. This will clear most temporary fault codes. If the error code reappears, write it down and consult your owner’s manual or call a qualified service professional for diagnosis.

Can I ignite my Navien during a power outage?

Unfortunately, no. Because the entire ignition process—including the control board, sensors, and igniter—relies on electricity, the unit cannot function during a power outage. For homes where consistent hot water is critical, some homeowners install a small battery backup (UPS) specifically for their tankless water heater.

You’re now equipped with the knowledge to understand and manage your Navien’s ignition system. By following these safe, simple checks, you can often resolve the issue of no hot water yourself. Remember to prioritize safety, and when in doubt, don’t hesitate to call a trusted HVACR professional.

Stay safe, stay warm, and enjoy that endless hot water!

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.