Clean And Descale Navien Tankless Water Heater - The Pro'S Method For

Is your morning shower starting to feel a little… lukewarm? Or maybe you’re hearing a faint rumbling or popping sound from your Navien unit that wasn’t there before. These are the classic signs that your high-efficiency water heater is crying out for help, and I’m here to tell you that it’s completely normal and, more importantly, something you can likely fix yourself.

I promise that by following this guide, you can safely and effectively clean and descale navien tankless water heater units, restoring that powerful, on-demand hot water you love. We’ll walk through this together, just like I would with a new apprentice on a service call.

In this comprehensive guide, we’ll cover exactly why this maintenance is so critical, the tools you’ll need for the job, a detailed step-by-step process, and some pro tips that will keep your system running at peak efficiency for years to come. Let’s get that water heater back in top shape.

Why You Absolutely Must Clean and Descale Your Navien Tankless Water Heater

Before we grab any tools, it’s crucial to understand why we’re doing this. Think of it like changing the oil in your car. It’s preventative maintenance that pays huge dividends in performance and longevity, and it’s one of the most important parts of any good clean and descale navien tankless water heater care guide.

The Hidden Enemy: Limescale Buildup Explained

The water coming into your home contains dissolved minerals like calcium and magnesium. While harmless to you, these minerals come out of solution when heated inside your Navien’s intricate heat exchanger. Over time, they form a hard, crusty layer called limescale.

This scale acts like an insulator, forcing your water heater to work much harder to heat the water. This not only wastes energy but also puts immense stress on the unit’s components, leading to premature failure. It’s the number one enemy of any tankless system.

The Tangible Benefits of Regular Descaling

Staying on top of this simple task delivers real, noticeable results. The benefits of clean and descale navien tankless water heater maintenance are immediate and long-lasting.

Restored Efficiency and Lower Bills: By removing the insulating scale, you allow the heat exchanger to transfer heat directly to the water, just as it was designed to. This means it uses less gas, saving you money on your utility bills.
Consistent, Powerful Hot Water: Scale buildup can restrict water flow, leading to pressure drops and temperature fluctuations. A clean unit delivers the steady, powerful hot water you expect.
Longer Equipment Lifespan: Reducing the strain on the heat exchanger and other components is the single best thing you can do to extend the life of your investment and avoid costly replacement.
Quieter Operation: That rumbling or “kettling” sound is often caused by water boiling and popping in pockets trapped by scale. Descaling smooths things out for silent operation.

Gathering Your Tools: The Descaling Toolkit

Alright, let’s get our gear together. Having everything ready before you start makes the process smooth and stress-free. You can buy a pre-made descaling kit, or you can assemble these parts yourself.

Submersible Utility Pump: A small 1/6 HP pump is perfect for this. You don’t need a massive sump pump.
A 5-Gallon Bucket: This will hold your cleaning solution. Make sure it’s clean before you start.
Two Washing Machine Hoses: Standard 3-4 foot hoses with female garden hose connectors on both ends work perfectly.
Descaling Solution: You have a couple of options here, which we’ll discuss below.
Channel-Lock Pliers or an Adjustable Wrench: For loosening and tightening hose connections.
An Old Towel: To catch any minor drips and spills.

Choosing the Right Descaling Solution

Your choice of solution is important. For a more eco-friendly clean and descale navien tankless water heater approach, plain white vinegar is a great choice. It’s non-toxic and readily available.

You’ll need about 2-3 gallons of undiluted white vinegar. It works well but may take slightly longer to dissolve heavy scale. For a faster, more powerful clean, you can use a food-grade, non-toxic descaling solution specifically designed for potable water systems. Always follow the manufacturer’s dilution instructions for commercial products.

Pro Tip: Avoid harsh chemicals like CLR or other acidic cleaners not rated for potable water systems. They can be too aggressive and may damage the sensitive components inside your Navien.

How to Clean and Descale Navien Tankless Water Heater: A Step-by-Step Guide

Here we go—the main event. Follow these steps carefully, and don’t rush. This entire process should take about 60-90 minutes. This is your ultimate clean and descale navien tankless water heater guide.

Safety First! Before you touch anything, ensure you cut power to the water heater. You can do this by unplugging it or shutting off the corresponding breaker at your electrical panel.

Turn Off the Gas Supply. Locate the gas valve on the line leading to your Navien unit. The handle should be perpendicular to the pipe when it’s off. It’s a simple quarter-turn valve.
Isolate the Water Heater. Your Navien should have isolation valves installed. These have a hot (red) valve, a cold (blue) valve, and a service (or purge) port on each. Turn the main red and blue valve handles perpendicular to the pipes to stop water from entering or leaving the unit.
Relieve the Pressure. Carefully twist the small T-shaped handles on the purge ports to open them. A little water will spurt out—this is normal. This step ensures you don’t get sprayed when connecting your hoses.
Connect Your Hoses. Attach one hose to the cold water purge port (the outlet) and place the other end into your 5-gallon bucket. Attach the second hose to the hot water purge port (the inlet) and connect the other end to your submersible pump. Place the pump inside the bucket.
Prepare and Add the Solution. Pour your descaling solution (either the vinegar or the prepared commercial solution) into the bucket. Make sure there’s enough liquid to completely submerge the pump.
Circulate the Solution. Plug in your submersible pump. You should see the solution being pumped from the bucket, through the hot water port, into the Navien’s heat exchanger, out the cold water port, and back into the bucket. Let this circulate for at least 60 minutes. If your water is very hard, you can go up to 90 minutes.
Flush the System. After circulating, unplug the pump. Dump the used solution (vinegar can go down the drain; follow disposal instructions for commercial products). Keep the hoses connected as they are, but close the hot water purge port (red side). Keep the cold water purge port (blue side) open, with the hose still draining into the bucket.
Open the Main Cold Water Valve. Slowly turn the main blue valve handle back to the parallel (on) position. Fresh water will now flow through the unit, pushing out any remaining solution and debris into the bucket. Let this run for a solid 5-10 minutes until the water runs completely clear and you no longer smell vinegar.
Return to Normal Operation. Close the main cold water valve again. Then, close the cold water purge port. Disconnect both hoses (have your towel ready for drips!). Return the main hot and cold valve handles to their parallel (on) positions. Finally, turn your gas supply back on and plug the unit back in or flip the breaker on.
Check Your Work. Go to the nearest hot water tap and turn it on. You’ll hear some air sputter out at first—this is normal. Let it run until you have a smooth, steady stream of hot water. Congratulations, you’re done!

Pro Tips and Best Practices for Navien Care

Doing the job is one thing, but doing it like a pro involves a few extra considerations. Here are some clean and descale navien tankless water heater tips that will make a difference.

How Often Should You Descale?

This is the most common question I get. The answer depends entirely on your water hardness.

Soft Water: Every 2-3 years is likely sufficient.
Moderately Hard Water: Annually is the best practice. This is the most common scenario.
Very Hard Water: You may need to descale every 6-9 months to prevent issues.

A simple water test kit can tell you your water hardness in “grains per gallon” (GPG). Anything over 7 GPG is considered hard, and annual maintenance is highly recommended.

Don’t Forget the Inlet Water Filter!

Your Navien has a small screen filter on the cold water inlet. While the system is drained and isolated, it’s the perfect time to check and clean it. Simply unscrew the inlet connection, carefully pull out the filter, rinse it under a tap to remove any sediment, and pop it back in. This is a common source of flow problems.

Recognizing When It’s Time to Call a Professional

This DIY guide covers routine maintenance. However, if you’ve descaled your unit and are still experiencing problems like error codes, no hot water at all, or water leaks, it’s time to put the tools down. These issues point to problems beyond simple scale buildup, and a qualified technician should diagnose them.

Common Problems with Clean and Descale Navien Tankless Water Heater Procedures

Even a straightforward job can have a hiccup. Here are a few common problems with clean and descale navien tankless water heater flushing and how to handle them.

My Pump Isn’t Circulating

If you plug in the pump and nothing happens, first check that it’s fully submerged. If it is, you might have an airlock. Try briefly lifting the pump out of the water and submerging it again to “burp” it. Also, double-check that both purge port valves are fully open.

I Still Have Low Hot Water Pressure

If descaling didn’t fix your pressure issues, the culprit is almost certainly a clogged filter. Check the main inlet water filter on the Navien unit itself, but also check the small aerator screens on your individual faucets and showerheads, as they can get clogged with dislodged scale.

Sustainable and Eco-Friendly Descaling Practices

Maintaining your equipment is inherently sustainable, as it prevents waste and reduces energy consumption. For a truly sustainable clean and descale navien tankless water heater process, focus on your materials.

Using plain white vinegar is the most eco-friendly option. It’s biodegradable and non-toxic. When you’re done, the used vinegar can be safely poured down the drain. This avoids introducing harsh chemicals into the water system, making it a responsible choice for your home and the environment.

Frequently Asked Questions About Navien Descaling

Can I use CLR to descale my Navien?

It’s strongly recommended that you do not use CLR or similar harsh chemical cleaners. They can be too corrosive for the copper and other sensitive metals in the heat exchanger, potentially causing permanent damage. Stick with food-grade vinegar or a descaler specifically formulated for potable water heaters.

How long does it take to clean and descale a Navien tankless water heater?

The entire process typically takes between 60 and 90 minutes. The longest part is simply letting the solution circulate for an hour. The actual hands-on time for setup and flushing is only about 20-30 minutes.

What happens if I never descale my tankless water heater?

If left unchecked, limescale will continue to build up until it severely restricts water flow and chokes the heat exchanger. This will lead to skyrocketing energy bills, frustratingly low hot water pressure, and ultimately, a complete failure of the unit, requiring a very expensive replacement.

By taking an hour or so each year for this simple maintenance, you’re not just getting better hot water—you’re protecting your investment and ensuring your Navien serves you well for its full lifespan. You’ve got this!

Stay safe, 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.