How to Flush a Navien Tankless Water Heater?

Flushing your Navien tankless water heater might not be the most glamorous task, but it’s a crucial part of ensuring its efficiency and longevity. In this guide, we’ll walk you through the steps to effectively flush your Navien tankless water heater, and why it matters. Tankless water heaters, such as Navien units, are known for their energy efficiency and endless hot water supply. 

To maintain their optimal performance, in addition, regular maintenance is crucial. Moreover, flushing your Navien tankless water heater helps remove sediment and scale buildup, ensuring it continues to provide hot water efficiently. Consequently, this step-by-step guide will walk you through the process of flushing your Navien tankless water heater.

The Benefits of Flushing Your Navien Tankless Water Heater

Flushing your Navien tankless water heater provides several benefits, which make it an essential part of routine maintenance.

Enhanced Energy Efficiency

Over time, mineral deposits and sediment can accumulate in your tankless water heater. Consequently, these deposits act as insulators, making it harder for the unit to heat water effectively. However, flushing removes these obstructions, allowing the heater to operate more efficiently. As a result, this increased efficiency translates to energy savings and lower utility bills.

Extended Lifespan

Regular flushing helps prolong the life of your Navien tankless water heater. When the unit operates efficiently and without the hindrance of mineral buildup, it experiences less wear and tear, reducing the need for premature replacements.

Consistent Hot Water Supply

Flushing ensures that the water flows freely through the unit without obstructions. This results in a consistent and reliable supply of hot water, especially during peak demand times. You won’t have to worry about sudden drops in water temperature during your showers or other activities.

Reduced Risk of Repairs

Neglecting maintenance can lead to costly repairs down the road. Moreover, flushing your Navien tankless water heater is a preventive measure that can save you money by preventing issues caused by scale and sediment buildup. Consequently, a well-maintained unit is less likely to suffer from breakdowns or component failure.

Cleaner Water

As you flush your tankless water heater, you not only clean the unit but also the water it provides. Sediment buildup can affect the quality of your hot water, potentially causing discoloration or an unpleasant odor. Flushing helps maintain clean and clear hot water, ensuring it’s safe and pleasant to use.


An efficiently operating tankless water heater is not only good for your wallet but also for the environment. When the unit functions optimally, it uses less energy and produces fewer greenhouse gas emissions. Regular flushing contributes to a greener and more sustainable home.

Equipment and Materials You’ll Need

  • A screwdriver
  • A pump kit (including a submersible pump)
  • Two 5-gallon buckets
  • Two hoses
  • Distilled white vinegar
  • A bucket of clean, fresh water
  • An adjustable wrench
  • Safety goggles and gloves

The Step-by-Step Guide

Step 1:

To inspect the gas line on your Navien water heater, begin by examining it closely. Subsequently, follow the line to the back of the heater, where you’ll find the gas shutoff valve. In most cases, the gas line starts at the front and extends to the rear of the unit. It is essential to ensure that the handle is perpendicular to the pipe, effectively turning it off to cut the gas supply to the heater.

Step 2:

To ensure the safety of the flushing process, start by powering off the unit. Additionally, locate a red button at the bottom of your water heater. Next, press and hold it for a few seconds to ensure the Navien unit is turned off.

Step 3:

Now, it’s time to shut off the water supply to your tankless water heater. Typically, immediately below the Navien unit, you’ll find the water shutoff valve.

Step 4:

To access the inner components, you’ll need to remove the cover of your Navien tankless water heater. Typically, the cover is secured with four screws – two at the top and two at the bottom. Subsequently, carefully unscrew these fasteners and lift off the cover, setting it aside.

Step 5:

Unplug the Power Ensure that the power to your Navien water heater is disconnected. This is an important safety step to avoid any electrical mishaps during the flushing process.

Step 6:

Clean the Cold Air Intake Filter It’s crucial to clean the cold air intake filter since it can accumulate debris, insects, and dirt. To access it, locate a screw on the front left of the intake housing. Loosen this screw slightly. 

There’s another screw on the front of the filter; remove it, allowing you to slide the screen out. Use a dry toothbrush to clean the filter thoroughly. Reinsert it into place once it’s clean. Avoid using a wet toothbrush, as it may make debris stick to the filter.

Step 7:

Reinsert the Filter. Next, place the cleaned filter back into its designated slot and slide it into place, ensuring the screw holes line up. Finally, secure the filter in place by screwing it back in.

Step 8:

Drain the Water Heater Now, it’s time to drain the water heater, which involves several valves. Here’s the process:

  • Turn off both the cold water inlet valve and the hot water valve to isolate the water heater.
  • Look for the smaller pipes, one red and one blue, known as “service valves.” Remove the caps from these valves.
  • Connect hoses to the service valves and open them to allow the water heater to drain into a bucket.
  • Once the hoses are connected, you can safely open the valves. Allow the water heater to drain for a few minutes until no more water comes out.

Step 9:

Clean the Base Locate the cold water filter to the right of the cold water isolation valve. Open it carefully while placing a bucket underneath. Some water may escape; however, you might notice residue, brown discoloration, or debris on the filter. Therefore, gently clean the filter using a toothbrush.

Step 10:

Reinstall the Filter Place the filter back on manually and give it an additional 1/8th turn using your tool for a secure fit.

Step 11:

Manage the “Dirt-Trap” Look for a pin beneath your water heater, remove it entirely, and pull the traps down. The O-ring should be on the first layer. Inside, you may find some dirt. Clean it with water and then place the O-ring and pin back in place.

Step 12:

Descaling the Water Heater Now, you need to run white vinegar through the system to remove scaling inside your water heater. Follow these steps:

  • Pour two gallons of white vinegar into a 5-gallon bucket.
  • Use a sump pump and connect the cold service hose to it.
  • Place the pump in the bucket, ensuring the return side points into the bucket.
  • Pump the white vinegar into the cold side of your water heater, allowing it to circulate through the system and out the hot side.
  • Ensure that the large valves are in the “off” position while the service valves are in the “on” position.
  • Allow the vinegar to circulate through the cold side for 45 minutes.

Step 13:

Flush the System Begin by turning the service valves off and removing the hoses. Then:

  • Connect a standard garden hose to the hot side service valve. Subsequently, you can place the other end in a nearby bathtub to facilitate water flow through the isolation side.
  • To facilitate the process, open the service port on the hose side and the isolation valve on the cold side, allowing water to pass through the system. Consequently, it should exit from the hot water port.
  • Flush the vinegar out of your water heater by running clean water through it.

Step 14:

Turn Off the Hot Service Valve After flushing, turn off the service valve on the hot side.

Step 15:

Remove the Service Hose and Cap the Service Ports Remove the service hose and securely cap the service ports on both the hot and cold sides. Leave the service ports in the “off” position.

Step 16:

Turn On the Water Supply Restore the water supply to your water heater.

Step 17:

Turn On the Hot Water Turn on the hot

The Benefits of Regular Flushing

Flushing your Navien tankless water heater offers several advantages:

  • Enhanced Efficiency: Removing mineral build-up ensures your heater operates at its best, reducing energy consumption and lowering utility bills.
  • Prolonged Lifespan: Regular flushing can extend your heater’s life, delaying the need for a costly replacement.
  • Consistent Hot Water Supply: Flushing guarantees a steady supply of hot water, even during peak usage times.
  • Reduced Maintenance Costs: Preventative maintenance through flushing can help you avoid costly repairs down the road.

Summary Table: Benefits of Flushing Your Navien Tankless Water Heater

Enhanced Energy EfficiencyFlushing increases the heater’s efficiency, leading to energy savings.
Extended LifespanRegular maintenance prolongs the unit’s life and reduces the need for replacements.
Consistent Hot Water SupplyFlushing ensures a reliable supply of hot water, even during peak demand times.
Reduced Risk of RepairsPreventative flushing minimizes the likelihood of costly repairs and component failures.
Cleaner WaterMaintaining clean, clear hot water for safer and more pleasant use.
Eco-FriendlyAn efficiently operating unit is both cost-effective and environmentally friendly.


How often should I flush my Navien tankless water heater?

Flushing your Navien tankless water heater once a year is generally recommended to maintain optimal performance.

Can I use regular white vinegar for descaling?

Yes, regular white vinegar works effectively for descaling your tankless water heater.

Do I need professional help to flush my Navien tankless water heater?

While some homeowners choose to DIY, professional help is advisable for those unfamiliar with the process to avoid potential issues.

What happens if I skip regular flushing of my tankless water heater?

Skipping regular flushing can lead to reduced energy efficiency; moreover, it can result in a shorter lifespan and a higher risk of repairs.

Can flushing my Navien tankless water heater improve water quality?

Yes, flushing removes sediment and mineral buildup, resulting in cleaner and safer hot water.


Flushing your Navien tankless water heater isn’t just a chore; moreover, it’s an investment in its performance and durability. With the right equipment and our step-by-step guide, moreover, you can easily maintain your heater, ensuring it delivers hot water efficiently for years to come.

Maintaining your Navien tankless water heater through regular flushing is a simple, cost-effective, and highly effective way to ensure the unit’s longevity, energy efficiency, and quality of the hot water it provides. Additionally, it can help prevent issues associated with sediment buildup and maintain the heater’s peak performance.

Additionally, this proactive approach not only saves you money but also enhances your overall home comfort.

By following the outlined steps and considering the benefits, you can enjoy a continuous supply of hot water and lower energy bills while reducing your environmental footprint. Remember, a well-maintained tankless water heater is a reliable one.

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