Navien Nr 180A Tankless Water Heater Flushing Instructions - A Pro'S

Is your morning shower starting to feel a little less powerful? Do you hear a faint rumbling or “kettling” sound coming from your Navien tankless water heater? These aren’t just minor annoyances; they’re your water heater’s way of crying out for help.

That noise and pressure drop are classic signs of mineral scale buildup—the number one enemy of any tankless water heater. This limescale silently chokes your unit’s delicate internal pathways, forcing it to work harder, driving up your energy bills, and paving the way for costly breakdowns.

But here’s the good news. You can fight back. Imagine restoring that strong, steady flow of endless hot water, silencing those disruptive noises, and extending the life of your investment for years to come. It’s all possible with one simple, yet crucial, maintenance task.

This guide provides the complete, easy-to-follow navien nr 180a tankless water heater flushing instructions you need to safely and effectively descale your unit. We’ll walk through it together, just like a technician would. Let’s restore your Navien to peak performance.

Why Flushing Your Navien NR-180A Isn’t Just a Suggestion—It’s Essential

Think of the heat exchanger inside your Navien as the heart of the system. Water rushes through its narrow passages, absorbing heat instantly. But if you live in an area with hard water, invisible minerals like calcium and magnesium are hitching a ride.

Over time, these minerals cling to the walls of the heat exchanger, forming a rock-hard layer of scale. This is more than just a little buildup; it’s like cholesterol clogging an artery, creating serious problems.

Here are the benefits of navien nr 180a tankless water heater flushing instructions and why tackling this task is so important:

Restores Energy Efficiency: Scale acts as an insulator, forcing your heater’s burner to fire longer and hotter to heat the water. Flushing removes this barrier, allowing for maximum heat transfer and lowering your gas bill.
Boosts Water Pressure: As scale builds, it physically narrows the pipes inside the unit, restricting water flow. A good flush clears these blockages, bringing back the strong pressure you expect.
Extends Unit Lifespan: The single biggest cause of premature tankless water heater failure is a scale-damaged heat exchanger. Regular flushing is the best preventative medicine and a core part of any good navien nr 180a tankless water heater flushing instructions care guide.
Maintains Your Warranty: Many manufacturer warranties, including Navien’s, can be voided if the unit fails due to a lack of basic maintenance like descaling.
Quiets Operation: That rumbling or popping sound (called kettling) is caused by water getting trapped and boiling in pockets under the scale. Flushing eliminates the scale and the noise along with it.

Gathering Your Tools & Supplies: The Pro’s Checklist

Before we begin, let’s get everything you need in one place. Having the right tools makes the job smooth, safe, and effective. You can buy a pre-made “tankless flush kit” or assemble the parts yourself.

Here’s your shopping list:

A Submersible Utility Pump: Don’t skimp here. You need a pump with a flow rate of at least 350-400 gallons per hour (GPH) to create enough turbulence to scrub the scale away.
Two Washing Machine Hoses: Standard 3-5 foot hoses with female connections on both ends work perfectly.
A 5-Gallon Bucket: This will hold your descaling solution and catch the discharge.
Descaling Solution: You have two excellent choices.
- Food-Grade White Vinegar: You’ll need 2-3 gallons. This is a great eco-friendly navien nr 180a tankless water heater flushing instructions option. It’s non-toxic and readily available.
- Commercial Descaler: Products like Flow-Aide or Nu-Calgon are specifically designed for potable water systems. They work faster and are more potent if you have very hard water or haven’t flushed in a while.
Channel-Lock Pliers or an Adjustable Wrench: For snugging up hose connections.
Old Towels: To catch any drips when disconnecting hoses.
Safety Gear: Safety glasses and gloves are a must, especially if using a commercial descaler.

The Complete Navien NR-180A Tankless Water Heater Flushing Instructions: A Step-by-Step Guide

Alright, you’ve got your gear. Now it’s time for the main event. Follow these steps carefully, and don’t rush. This entire process should take about 90 minutes, with most of that time just letting the pump do its work.

This is the definitive how to navien nr 180a tankless water heater flushing instructions guide.

Step 1: Safety First – Isolate the Unit
Your safety is the top priority. Before you touch anything, you need to completely isolate the water heater.
- Turn OFF the power to the unit. You can either unplug it or switch off the corresponding circuit breaker.
- Turn OFF the gas supply. Find the gas valve on the line leading to your Navien (it usually has a yellow or red handle) and turn it so the handle is perpendicular to the pipe.
Step 2: Locate and Close the Main Water Valves
Your Navien should have been installed with a set of isolation valves. You’ll see three T-shaped handles: a blue one on the cold water line, a red one on the hot water line, and one on the main gas line. Turn the blue and red handles so they are perpendicular to the pipes they are on. This stops water from entering or leaving the unit from your home’s plumbing.
Step 3: Connect Your Flush Hoses
On those same isolation valves, you’ll see small, spigot-like service ports with little handles.
- Unscrew the caps from the cold water service port (blue side) and the hot water service port (red side).
- Connect one of your hoses to the cold water port. Place the other end of this hose into your empty 5-gallon bucket.
- Connect your second hose to the hot water port. Attach the other end of this hose to the outlet of your submersible pump.
Step 4: Prepare and Circulate the Descaling Solution
Pour your chosen descaling solution (2-3 gallons of white vinegar or a prepared commercial solution) into the bucket. Place your submersible pump at the bottom of the bucket, making sure it’s fully submerged. Now, open the little T-handles on the hot and cold service ports by turning them parallel to the port outlets.
Plug in your pump. You should see the solution get sucked out of the bucket, through the pump, into the hot port, through the heat exchanger, and out the cold port back into the bucket. This reverse flow is crucial for breaking scale loose. Let the pump run continuously for at least 60 minutes.
Step 5: Flush the System with Clean Water
After 60 minutes, unplug the pump. Carefully dump the used descaling solution (it will likely be discolored with sediment). Rinse the bucket thoroughly and refill it with 3-4 gallons of clean water. Place the pump back in the bucket and run it for another 5-10 minutes to flush every trace of the descaler from the unit.
Step 6: The Pro-Tip: Clean the Inlet Filter!
This is one of the most overlooked but critical navien nr 180a tankless water heater flushing instructions tips. Before restoring water, you must clean the small filter on the cold water inlet.
- Unplug the pump and close the service port valves. Disconnect your hoses (have towels ready!).
- On the bottom of the unit, find the cold water connection. Right there, you’ll find a small screen filter. Carefully unscrew the housing, remove the filter, and rinse it under a faucet until it’s perfectly clean.
- Re-install the filter and screw the housing back on snugly. This step prevents any dislodged debris from immediately clogging your system.
Step 7: Restore Your System and Test
You’re in the home stretch! Follow these steps in order:
- Make sure your service port caps are screwed back on tightly.
- Slowly open the main cold water valve (blue handle).
- Slowly open the main hot water valve (red handle).
- Go to the faucet closest to the unit (like a utility sink) and turn on the hot water. It will sputter as air purges from the lines. Let it run until you have a smooth, steady stream.
- Once the water is running smoothly, restore power and turn the gas supply back on.
- Your Navien should fire up, and you’ll have clean, powerful, and efficient hot water once again!

Best Practices for a Flawless Flush

Following a good navien nr 180a tankless water heater flushing instructions guide is key, but a few extra tips can make the process even better. These are the best practices we follow in the field.

How Often Should I Flush My Navien?

This depends entirely on your local water hardness.

Very Hard Water (10+ GPG): Plan on flushing every 9-12 months.
Moderately Hard Water (5-9 GPG): Every 12-18 months is a good schedule.
Soft Water (0-4 GPG): You can likely go 2-3 years between flushes.

If you’re unsure, you can buy a simple water hardness test kit online or from a home improvement store.

Common Problems with Navien NR-180A Tankless Water Heater Flushing Instructions

Even with the best instructions, hiccups can happen. Here’s how to troubleshoot them:

Pump Won’t Prime or Circulate: Ensure the pump is fully submerged in the solution and that there are no kinks in your hoses.
Leaky Hose Connections: Use your pliers to gently snug the connections. Don’t overtighten. Check that the rubber gaskets inside the hose ends are present and in good shape.
Low Pressure After Flushing: You likely forgot to clean the inlet water filter. Go back to Step 6 and clean that screen!

When to Call a Professional HVAC Technician

While this is a very manageable DIY task, there are times when it’s best to call for backup. Your safety and the health of your equipment are what matter most.

Pick up the phone and call a licensed technician if:

You are uncomfortable with any part of the process.
The unit continues to show an error code after a successful flush.
You notice any water leaking from the body of the unit itself, not just the temporary hose connections.
Your water pressure or temperature issues persist after flushing.
You don’t have the proper isolation valves installed, making the flush impossible to perform safely.

Frequently Asked Questions About Navien NR-180A Flushing

Can I use CLR to flush my Navien tankless water heater?

We strongly advise against it. Products like CLR can be overly corrosive and may damage the sensitive rubber seals, gaskets, and electronic sensors inside your Navien. Always stick with food-grade white vinegar or a descaler specifically formulated for potable (drinkable) water systems.

What happens if I never flush my tankless water heater?

The consequences are predictable and expensive. First, your energy bills will slowly creep up. Then, your water pressure will drop. Finally, the heat exchanger will become so clogged that it either cracks from the stress or triggers persistent shutdown errors, requiring a replacement that can cost nearly as much as a new unit.

How long does it take to flush a Navien NR-180A?

Set aside about 90 minutes to two hours from start to finish. The hands-on time for setup and takedown is only about 20-30 minutes. The majority of the time—60 minutes or more—is simply letting the pump circulate the solution and do the hard work for you.

Congratulations! By following these navien nr 180a tankless water heater flushing instructions, you’ve performed one of the most important pieces of preventative maintenance for your home. You’ve not only improved your Navien’s performance today but also helped ensure it provides reliable, efficient hot water for many years.

Taking care of your home’s systems is empowering, and we’re here to help every step of the way. 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.