Tankless water heaters are fantastic pieces of equipment, providing endless hot water and saving your customers money on their utility bills. But as any experienced plumber knows, these units require consistent care to keep them running smoothly. Navien models are incredibly popular in the field, known for their high efficiency and innovative condensing technology. Yet, just like any other water heater, they are vulnerable to the hard water found in places like Arizona, Nevada, and Texas.
When mineral deposits build up inside the heat exchanger, performance drops, energy bills rise, and frustrating error codes start flashing. That means you get an emergency call from a customer with no hot water. Knowing exactly how to flush navien tankless water heater units efficiently is a vital skill for your plumbing business. It saves you time, prevents costly replacement parts, and keeps your clients happy.
This guide breaks down the entire process. We will cover why regular flushing is so important, the essential tools you need to get the job done, and a detailed step-by-step walkthrough. You will also learn how to troubleshoot common issues and pick up a few pro tips to maximize the lifespan of every Navien unit you service.
Why Flushing Your Navien Tankless Water Heater is Crucial
Every time water passes through a tankless system, trace amounts of minerals are left behind. Over time, these minerals form a hard layer of scale. Removing this scale is not just a recommendation; it is an absolute requirement for proper system function.
Preventing Mineral Buildup and Scale
Calcium and magnesium are the primary culprits behind scale buildup. When hard water is heated rapidly, these minerals precipitate out of the water and stick to the narrow passages of the stainless steel heat exchanger. If you do not flush the system, this scale restricts water flow and acts as an insulator, forcing the burner to work significantly harder to heat the water to the desired temperature.
Maintaining Efficiency and Performance
Navien units boast incredible efficiency ratings, often up to 0.96 UEF. However, scale buildup destroys that efficiency. By pumping a descaling solution through the system, you dissolve the mineral deposits. This restores the unit’s ability to transfer heat effectively, ensuring your customers get the fast, reliable hot water they expect while keeping their energy bills low.
Extending the Lifespan of Your Unit
A water heater that constantly overheats or struggles to push water through clogged pipes will burn out much faster than a well-maintained one. Routine flushing prevents the internal components from working under extreme stress. Taking the time to perform this service can easily add years to the operational life of the unit, protecting your customer’s investment.
Identifying Signs That Your Unit Needs Flushing
How do you know when it is time to flush a unit? Your customers might complain that the water takes too long to get hot, or they might notice a drop in water pressure. You might also hear strange rumbling or popping noises coming from the heater. Navien units are smart, and they will often tell you when there is a problem. Keep an eye out for error codes like E016, E110, or E003, which frequently point to flow restrictions or exhaust issues caused by lack of maintenance.
Essential Tools and Materials for Flushing
Showing up to the job site with the right supplies saves you a trip back to the warehouse. Before you start, make sure you have everything you need to perform a seamless flush.
Flushing Kit
You will need a reliable submersible pump to circulate the cleaning solution. Pair this with a clean 5-gallon bucket. You will also need two washing machine hoses to connect the pump and bucket to the water heater’s isolation valves.
White Vinegar or Specialized Descaling Solution
White vinegar is a safe, effective, and inexpensive option for breaking down scale. Many professionals prefer to use about four gallons of food-grade white vinegar. Alternatively, you can use a manufacturer-approved commercial descaling solution, which often works a bit faster.
Adjustable Wrench, Screwdriver, Towels
Keep an adjustable wrench handy for tightening and loosening the hose connections. You will need a screwdriver (preferably magnetized) to remove the front panel and access the internal filters. Finally, always keep a few dry towels nearby to catch any stray drips and keep the work area spotless.
Step-by-Step Guide: How to Flush Navien Tankless Water Heater
Ready to get to work? Follow these exact steps to clean the heat exchanger and get the system back in peak condition.
Preparation
Safety always comes first. Before you introduce any cleaning solutions, you need to isolate the water heater from the rest of the home’s plumbing.
1. Turn off power and gas supply
Locate the power button on the front display and turn the unit off. Next, unplug the unit from the wall outlet or flip the dedicated circuit breaker. Finally, locate the gas line connected to the bottom of the heater and turn the gas valve to the closed position.
2. Close water isolation valves
Look beneath the unit for the hot and cold water service valves. Turn the handles on both the main cold water inlet and the main hot water outlet so they are perpendicular to the pipes. This stops water from entering the heater and prevents your cleaning solution from flowing into the home’s water supply.
3. Connect hoses to purge ports
Remove the caps from the hot and cold service ports. Connect one washing machine hose to the cold water service port, and attach the other end to your submersible pump. Place the pump inside your 5-gallon bucket. Next, connect your second hose to the hot water service port, and leave the other end hanging freely inside the bucket. If you are working on an “A” series model with a recirculation pump, you may need a third hose for the recirculation outlet.
Flushing Process
Now that the unit is isolated, you can begin the actual descaling process.
1. Introduce descaling solution
Pour your white vinegar or commercial descaling fluid into the 5-gallon bucket. Make sure there is enough liquid to completely submerge the pump. Open the service port valves on both the hot and cold sides.
2. Circulate solution through the system
Plug in your submersible pump. The pump will push the vinegar into the cold side of the water heater, force it through the heat exchanger, and push it out the hot side back into the bucket. Let this solution circulate continuously for at least 45 minutes to dissolve stubborn mineral deposits.
3. Drain and rinse thoroughly
Once the 45 minutes are up, turn off the pump. Close the cold water service port valve, but leave the hot side open. Remove the pump from the bucket and properly dispose of the used vinegar. Now, open the main cold water isolation valve. Fresh water will rush into the unit and push any remaining vinegar out through the hot service port hose into your empty bucket or a nearby drain. Let this run for about five minutes to thoroughly rinse the system.
Post-Flushing
The system is clean, but your job is not quite done. You need to check the filters and safely restore power.
1. Disconnect hoses
Close the main cold water valve again. Close the hot service port valve. Carefully disconnect your hoses from both service ports and replace the caps securely.
2. Clean the filters
While the unit is drained, unscrew the cold water inlet filter screen located at the bottom of the unit. Rinse it under cold water and use a soft brush to remove any trapped debris. If it is an NPE-A model, do the same for the recirculation filter. Next, remove the front cover of the unit and locate the air intake filter near the top. Remove the securing screw, pull the filter out, wash it, dry it completely, and reinstall it.
3. Open water valves and restore power/gas
Open both the main cold water inlet and the main hot water outlet valves. Check your service port caps to ensure nothing is dripping. Turn the gas valve back on, plug the unit back in, and press the power button. Go to a nearby sink and turn on the hot water to purge any trapped air from the lines and verify the system is firing up correctly.
Troubleshooting Common Flushing Issues
Sometimes, things do not go perfectly according to plan. Here is how to handle a few common hiccups.
Low Flow or Pressure After Flushing
If the water pressure seems weak after you finish the job, check the inlet filter screens again. It is highly possible that a large chunk of scale broke loose during the rinse cycle and became lodged in the screen. Simply turn the water off, pull the filter, and clean it one more time.
Persistent Error Codes
If the unit is still throwing an E110 or E016 error code, double-check the air intake and exhaust pipes. Flushing cleans the water side of the system, but an obstructed vent pipe will still cause the unit to shut down for safety. Ensure the air filter is completely dry and properly seated.
Leaks From Connections
If you spot water dripping from the bottom of the unit, grab your adjustable wrench. Ensure the service port caps are screwed on tight and that the rubber O-rings inside the caps are not damaged or missing.
Frequency of Flushing
How often should you schedule this service for your customers? It depends heavily on the local water conditions.
General Recommendations Based on Water Hardness
For the average home, Navien recommends flushing the heat exchanger once a year. This annual maintenance is usually enough to keep the unit running efficiently and protect the manufacturer’s warranty.
Regional Considerations
If you operate in areas with notoriously hard water, such as parts of Arizona, Nevada, or Texas, once a year might not cut it. In these regions, you should advise your customers to have their units flushed every six to eight months to prevent severe calcification.
Professional vs. DIY Flushing
Some homeowners try to tackle this job themselves. However, as a professional, you know that without the right tools, isolation valves, and knowledge of the unit’s electronics, DIY flushing can lead to disaster. Remind your customers that hiring a pro guarantees the job is done safely, ensures all internal filters are cleaned correctly, and keeps their warranty intact.
Tips for Optimal Navien Tankless Water Heater Performance
Flushing is the most important part of tankless maintenance, but you can offer your customers a few extra solutions to optimize their plumbing systems.
Water Softener Installation
The best way to deal with scale is to prevent it from entering the heater in the first place. Recommending a whole-home water softener or a dedicated anti-scale system, like the Navien PeakFlow, is a great upsell. These systems treat the water before it hits the heat exchanger, drastically reducing the frequency of required flushes.
Regular Visual Inspections
Encourage your customers to occasionally look at their unit. They should check for any obvious signs of leaks around the pipes, listen for unusual noises, and keep the area around the air intake completely clear of dust, lint, or stored boxes.
Professional Servicing
Set up your customers on a recurring maintenance plan. By keeping track of when their unit is due for a flush, you guarantee recurring revenue for your business while providing a seamless, stress-free experience for the homeowner.
Keep the Hot Water Flowing
Learning how to flush navien tankless water heater units is an essential part of being a successful plumbing professional. By removing destructive mineral scale, you restore the unit’s high efficiency, prevent annoying error codes, and ensure the system lasts for years to come.
Equip your service trucks with the right pumps, hoses, and high-quality descaling solutions. By offering flat-rate tankless maintenance, you build deep trust with your customers and position your plumbing business as their go-to partner for all their hot water needs.