Flushing A Navien Tankless Water Heater

Tankless water heaters, especially those from Navien, offer a compelling alternative to traditional tank-style units. Their on-demand heating provides endless hot water and can potentially save space and energy. However, like any mechanical system, they require regular maintenance to ensure optimal performance and longevity. A critical aspect of this maintenance is flushing the system to remove mineral buildup.

Understanding Scale and Its Impact

The water flowing through your Navien tankless water heater isn't pure H₂O. It contains dissolved minerals like calcium and magnesium. When heated, these minerals can precipitate out of the water and form a hard, chalky deposit called scale. Think of it like the buildup you see in your tea kettle or on showerheads. This scale primarily accumulates on the heat exchanger, the component responsible for heating the water.

Scale buildup acts as an insulator, reducing the efficiency of the heat exchanger. Your Navien unit will have to work harder to heat the water, leading to:

Increased energy consumption and higher utility bills.
Reduced hot water flow rate. You might notice a weaker shower or longer wait times.
Overheating and potential damage to the heat exchanger. This can lead to costly repairs or premature failure of the unit.
Error codes displayed on the unit indicating a problem. Navien units are equipped with sensors to detect scale buildup and trigger warnings.

The severity of the scaling problem depends on the water hardness in your area. If you live in a region with hard water, you'll need to flush your Navien tankless water heater more frequently. A water softener can significantly reduce scale buildup, but regular flushing is still necessary.

Frequency of Flushing

Navien recommends flushing their tankless water heaters at least once a year, or more frequently if you have hard water. Consult your Navien unit's manual for specific recommendations. The manual often suggests flushing every 6 months if your water hardness exceeds a certain threshold, usually measured in grains per gallon (GPG) or parts per million (PPM).

Consider these factors when determining your flushing schedule:

Water Hardness: Test your water regularly. You can purchase a water hardness testing kit at most hardware stores or have a professional test it.
Water Usage: Higher water usage means more minerals passing through the unit and potentially more scale buildup.
Unit Age: Older units may be more susceptible to scale buildup due to years of mineral deposition.

Materials Required for Flushing

To flush your Navien tankless water heater, you'll need the following:

Submersible Pump: A small utility pump capable of circulating cleaning solution. A pump with a flow rate of around 3-5 gallons per minute is usually sufficient.
Hoses: Two lengths of washing machine hose or similar hoses with threaded connections that fit your service valves and pump.
Bucket: A 5-gallon bucket to hold the cleaning solution.
Descaling Solution: Use a descaling solution specifically designed for tankless water heaters. Navien recommends using their own descaling solution, but other commercially available solutions like vinegar can also be used (with caution and according to the manufacturer's instructions for your unit). Never use harsh chemicals like muriatic acid, as they can damage the heat exchanger and other components.
Adjustable Wrench: To tighten hose connections.
Screwdriver: Depending on your unit, you may need a screwdriver to access the service valves.
Gloves and Eye Protection: To protect yourself from the cleaning solution.

Step-by-Step Flushing Procedure

Safety First: Before starting, turn off the power to your Navien tankless water heater at the circuit breaker. This prevents accidental activation of the unit during the flushing process.

Isolate the Unit: Locate the service valves on your Navien unit. These are typically located on the bottom of the unit, labeled "Hot" and "Cold." Close both valves to isolate the unit from your home's plumbing system.
Connect the Hoses: Connect one hose to the cold-water service valve and the other hose to the hot-water service valve. Place the open ends of both hoses into the bucket.
Prepare the Cleaning Solution: Mix the descaling solution with water in the bucket according to the manufacturer's instructions. Typically, this involves diluting the descaling solution with an equal amount of water.
Submerge the Pump: Place the submersible pump into the bucket, ensuring it is fully submerged in the cleaning solution.
Connect the Pump: Connect the pump's outlet to the hose attached to the cold-water service valve. This will pump the cleaning solution into the unit.
Circulate the Solution: Plug in the pump and allow the cleaning solution to circulate through the Navien unit for the recommended time, typically 30-60 minutes. Monitor the bucket for any leaks.
Flush with Clean Water: After circulating the cleaning solution, unplug the pump and remove it from the bucket. Empty the bucket and fill it with clean water. Repeat the process, circulating clean water through the unit for about 15-20 minutes to remove any remaining descaling solution.
Disconnect the Hoses: Turn off the service valves to prevent backflow. Disconnect the hoses from the service valves and the pump.
Open the Service Valves: Slowly open both the hot and cold-water service valves to restore water flow to the unit.
Restore Power: Turn the power back on to your Navien tankless water heater at the circuit breaker.
Test the Unit: Run hot water from a faucet to ensure the unit is functioning properly and that the water is heating correctly. Check for any leaks around the service valves and hose connections.

Troubleshooting

No Hot Water After Flushing: Double-check that the service valves are fully open and that the power is restored to the unit. If the problem persists, consult the Navien unit's manual or contact a qualified HVAC technician.

Error Codes: If you see an error code after flushing, consult the Navien unit's manual for troubleshooting steps. Some error codes may require professional assistance.

Leaks: Check all hose connections and service valves for leaks. Tighten connections as needed. If leaks persist, replace the hoses or contact a plumber.

Professional Flushing vs. DIY

While flushing a Navien tankless water heater is a manageable DIY project for many homeowners, there are situations where professional assistance is recommended:

Lack of Experience: If you're uncomfortable working with plumbing or electrical systems, it's best to hire a professional.
Complex Systems: Some Navien units are more complex than others, and require specialized knowledge to flush properly.
Severe Scale Buildup: If you suspect severe scale buildup, a professional may have access to stronger descaling solutions and specialized equipment to remove the deposits effectively.
Warranty Concerns: In some cases, DIY maintenance may void the warranty on your Navien unit. Check your warranty terms for details.

The cost of professional flushing typically ranges from $150 to $300, depending on the location and the complexity of the system. While this may seem like an expense, it can be a worthwhile investment to protect your Navien tankless water heater and ensure its longevity.

Preventative Measures

While flushing is essential, taking preventative measures can reduce the frequency and severity of scale buildup:

Water Softener: Installing a water softener can significantly reduce the amount of calcium and magnesium in your water, minimizing scale formation.
Water Filter: A whole-house water filter can remove sediment and other impurities from your water, further protecting your Navien unit.
Regular Inspections: Periodically inspect your Navien unit for signs of scale buildup, such as reduced flow rate or unusual noises.

Conclusion

Flushing your Navien tankless water heater is a critical maintenance task that can significantly extend its lifespan and maintain its efficiency. By understanding the importance of flushing, following the proper procedure, and taking preventative measures, you can ensure that your Navien unit provides you with years of reliable hot water.

By understanding the principles behind scale formation and the proper flushing techniques, you can make informed decisions about maintaining your Navien tankless water heater. Whether you choose to handle the flushing yourself or hire a professional, regular maintenance is key to ensuring the longevity and efficiency of your system.