How to Descale a Navien Tankless Water Heater

Descaling a Navien tankless water heater is an essential maintenance task that helps ensure the unit operates efficiently and remains in optimal condition. Over time, mineral deposits like calcium and lime can accumulate inside the heat exchanger, reducing performance and causing potential damage.

By regularly descaling your water heater, you can extend its lifespan, maintain consistent water temperatures, and prevent costly repairs. This guide will walk you through the necessary steps of how to descale a navien tankless water heater.

Why Descaling Is Important

Descaling your Navien tankless water heater is a crucial maintenance step that ensures the unit continues to function efficiently and reliably. Over time, mineral buildup from hard water can clog the heat exchanger and restrict water flow, significantly reducing the heater’s efficiency. This buildup forces the unit to work harder, leading to higher energy consumption and an increased risk of overheating or damage.

Regular descaling not only prevents these issues but also helps to maintain consistent water pressure and temperature, ensuring optimal performance. Additionally, by removing harmful deposits, you can extend the lifespan of your water heater and avoid expensive repairs or replacements down the line. Taking the time to descale the unit protects your investment and ensures uninterrupted access to hot water when you need it.

Tools and Materials Needed for Descaling

To successfully descale your water heater, you will need the following tools and materials:

• Descaling solution – A commercial descaling product or a mixture of white vinegar and water.
• Bucket – For draining and flushing the water heater.
• Hose – A garden hose that can be connected to the drain valve.
• Wrench or pliers – To open and close valves securely.
• Protective gloves – To prevent skin contact with the descaling solution.
• Safety goggles – To protect your eyes from splashes while handling the solution.
• Clean cloths or rags – For cleaning up spills or wiping components after the process.
• Screwdriver – Depending on your water heater model, a screwdriver might be required to access certain parts.

Having these tools and materials prepared in advance will make the descaling process more efficient and help ensure a thorough cleaning.

10 Methods How to Descale a Navien Tankless Water Heater

1. Turn Off the Power and Gas Supply

Before beginning the descaling process, it is vital to shut off all power to the unit to ensure your safety. Navien tankless heaters may be connected to either a standard outlet or hardwired into your electrical system. Unplug the unit or turn off the breaker if necessary. Also, close the gas supply valve to prevent any unintended operation. Turning off these utilities ensures there’s no risk of accidental ignition or electrical short circuits while you work with water and internal components.

2. Shut Off Water Supply and Isolate the Unit

Next, shut off both the cold-water inlet and the hot-water outlet valves to isolate the water heater from the household plumbing. Many Navien units come with a set of isolation valves, often referred to as a flush kit. These valves make it easier to perform maintenance without affecting the rest of the house. If your heater doesn’t have these pre-installed, consider installing a valve kit, as it simplifies descaling and helps avoid future plumbing complications.

3. Relieve Internal Pressure by Opening the Pressure Relief Valve

Before opening the service ports or attaching hoses, it’s important to relieve any pressure that may be trapped within the system. You can do this by slowly opening the pressure relief valve located on or near the water heater. Be cautious, as hot water might be released during this step. Allowing pressure to escape prevents sudden spurts of water and potential injury when connecting or disconnecting hoses later in the process.

4. Attach Hoses to the Isolation Valves

With pressure safely relieved, attach two garden hoses—one to the cold inlet valve and one to the hot outlet valve. These will form the loop that allows descaling solution to circulate through the heater. Ensure that the connections are secure and leak-free. One hose will draw the descaling solution into the water heater, while the other will carry it out to be recirculated or discharged. Use high-quality, kink-resistant hoses to avoid interruptions during the flushing process.

5. Use a Submersible Pump and a Bucket with Descaling Solution

Place a submersible pump in a 5-gallon bucket filled with a descaling solution. You can purchase a commercial descaler specifically formulated for tankless water heaters, or you can use white vinegar as a natural alternative. At least 4 gallons of solution is recommended for proper circulation. Connect the pump to the hose attached to the cold-water inlet. The hose on the hot-water outlet should return to the same bucket, completing the loop.

6. Circulate the Descaling Solution for 45–60 Minutes

Turn on the submersible pump and allow the descaling solution to circulate through the system. This flushing process typically takes 45 to 60 minutes. During this time, the acidic solution dissolves mineral deposits built up within the heat exchanger. Letting the solution recirculate continuously ensures all internal surfaces are treated and descaled evenly. You may notice bubbles or discoloration in the solution, which is a normal sign that scaling is being broken down and removed.

7. Drain and Dispose of the Used Descaling Solution Safely

Once the circulation cycle is complete, turn off the pump and disconnect the hoses from the heater. Carefully pour out the used descaling solution from the bucket, following local regulations for disposal. While white vinegar is biodegradable and can often be safely poured down a drain, commercial descalers may contain stronger acids and should be handled accordingly. Rinse the bucket and pump thoroughly to prevent corrosion and ensure they’re clean for future use.

8. Flush the Water Heater with Clean Water

To remove any residual descaling solution from the heater’s internal components, perform a fresh-water flush. Reconnect the cold-water hose to a fresh water source or simply reopen the cold-water inlet valve (with the hot-water outlet still connected to a drain or the bucket). Allow clean water to run through the system for 5–10 minutes. This rinses out any acidic residue, preventing potential damage or taste issues in your water supply.

9. Reconnect Plumbing, Restore Power, and Relight the Heater

Once the system is clean and flushed, disconnect all hoses and securely close the service valves. Open the cold- and hot-water supply valves to resume normal water flow to the heater. Plug the unit back in or switch on the breaker. If your unit uses gas, reopen the gas valve and follow your Navien model’s instructions to relight the pilot (if applicable) or allow the unit to self-ignite. Run hot water from a faucet briefly to confirm the system is functioning correctly.

10. Schedule Regular Maintenance to Prevent Future Scaling

The final—and arguably most important—method is to implement a maintenance schedule. Descaling should be done at least once a year, or every six months in areas with very hard water. Some Navien models will display an error code (like “002”) or a maintenance reminder when flushing is required. To reduce scale buildup in the long term, consider installing a whole-house water softener. This device reduces calcium and magnesium in the water before it enters the water heater, extending the intervals between descalings and improving the unit’s efficiency and lifespan.

Maintenance and Upkeep

Proper maintenance and upkeep of your Navien tankless water heater are essential to ensure optimal performance and longevity. Regularly inspect the exterior of the unit for any visible signs of damage or leaks. Clean the intake air filter every three to six months, as debris buildup can hinder airflow and reduce efficiency. Additionally, it’s important to check the venting system for obstructions or damage to maintain safe and effective operation.

Flush the heater annually to remove sediment and mineral buildup, as detailed in the descaling process. If your unit uses a condensate trap, empty and clean it periodically to prevent blockages. For units with freeze protection heaters, inspect these components before the onset of cold weather to ensure they are functioning properly. Always refer to the user manual for detailed instructions and consult a professional technician for any maintenance tasks beyond your expertise. Consistent care will help prevent costly repairs and maximize your water heater’s lifespan.

Safety Considerations

When performing maintenance on your water heater, it is crucial to prioritize safety to avoid injury or damage. Always disconnect the power supply and turn off the water source before beginning any maintenance tasks. If your water heater operates using gas, ensure the gas supply is also shut off to prevent leaks or accidents.

Use proper protective gear, such as gloves and safety goggles, especially when handling chemicals like descaling agents. Additionally, ensure that the area around the water heater is clear of flammable materials and well-ventilated if working with gas-powered units. If you’re uncertain about any procedures, consult a licensed professional to avoid risk. Taking these precautions will help ensure a safe and successful maintenance process.

Conclusion

Descaling a Navien tankless water heater is a vital maintenance procedure that ensures consistent performance and longevity. By methodically isolating the unit, circulating a cleaning solution, and flushing with fresh water, homeowners can successfully maintain their system with minimal risk. With attention to detail and regular care, a Navien heater can provide years of reliable hot water while remaining energy-efficient. Thanks for reading, and we hope this has given you some inspiration on how to descale a navien tankless water heater!