How to Flush Tankless Water Heater?

Tankless water heaters build up debris and calcium on its filter and also inside the machine. So it’s important to flush the whole water heater with food-grade like white vinegar at least once in every 12 to 18 months. As an expert, we must say that this simple maintenance must improve the efficiency and lifetime of your tank less water heater. At this simple maintenance time, it best to clean the air filter inside the tankless hot water heater at the time you are going to flushing your water heater. Here we provide instruction that will show clearly how to flush tankless water heater? We took a Takagi tankless water heater to make the steps more comfortable for you. But we assure that these instruction steps can applied to any tankless water heater as you can locate the corresponding components on your water heater.

Let's Follow The Steps To Clean Your Water heater

  • Step 1: Gather Your Flushing Materials

To complete this task, you're going to need:

  1. Five-gallon bucket.
  2. Two stainless steel washing machine hoses.
  3. A submersible pump.
  4. Four gallons of white food grade vinegar. (You can easily buy white food grade vinegar at any grocery store.)

Note: You can purchase all these materials from Amazon. Click to check the price: Tankless-Water-Heater-Cleaning-Kit.

  • Step 2: Locate the Shutoff Valves

In this step, you have to find out the color coded handles underneath your tankless water heater. These levers shut off the water and gas supply to your tankless water heater. If you see the levers are in line with the pipe that means it's ON and if it's vertical that means it's off. Now carefully turn them all vertical to the pipes. In that way, you can shut off the gas (A yellow handle attached on the right side to the water heater silver pipes, Central handle color is yellow, the cold blue one shows water intake, and the red one is hot water outflow pipes. Before following this step instruction please unplugs your unit from the wall socket.

  • Step 3: Unscrew Cold Water Service Valve

In this step, you have to unscrew the cold water service valve. You can find the service valve just above the red and blue levers. Now you have to turn the levers vertically to the pipe and shut off the water from your tankless water heater. But before opening the service valve, you have to read your materials first.

Precaution Note: There’s an external pump that attached to the wall near your floor. Its electronic components exposed through the vents at the top of the device. So you need to avoid getting any water on this device to reduce the short circuit or an unexpected accident. At the same time, be careful about to burn yourself during you open hot water pipes. So do your washing process slowly.

  • Step 4: Setup Your Vinegar and Pump

In this step empty your 5-gallon bucket of any water that you collected from the service valves by following the steps 3.

Now fill your empty bucket with 4 gallons of food-grade white vinegar and then attach the hose which is going into the cold water service valve into the top of the sump pump. But make sure all connections are connected tightly and don’t plug in the pump yet.

Now you can place the pump into the vinegar but doing this before plugging it into the wall. The most important thing is that there’s no On or Off switch, so it will turn on instantly the time you plug it into the wall socket. Again, make sure the hose going properly into the hot water service valve attached safely before plug the sump pump into the power outlet, and, the other end of sump pump placed into the bucket. That doesn’t need to screw into the pump, just loosely put it to the vinegar bucket. Now what you saw, the hoses are attached and the pump submerged in the vinegar. That means you're ready to begin the flushing of your tankless water heater.

  • Step 5: Start Circulating vinegar to clean water service valve

In this step, you can go ahead to plug in the pump into the power outlet. It starts to circulate the vinegar through the cold water service valve which color is blue and out vinegar through the hot water service valve which color is red and recycle into the same vinegar bucket. Now you have to leave the whole process for at least 60 to 90 minutes. In the manual manufacturer says go the process for 45 min but we figured it's been better to go longer to 60 to 90 minutes.

  • Step 6: Cleaning the Air Intake Filter

The time your vinegar circulating, you can also clean out the air intake filter. Because, if there’s an error message on your display that reads ``027`` then you need to clean the air intake filter.

You find the air intake filter which located inside the tankless water heater. Don’t worry it's not hard to open, remove the tankless water heater faceplate first. It held together with four screws, two on top and two on the bottom of the water heater body. After finding the air intake filter, at first, the very first moment, unscrew all the screws, then lift upwards to unlock the top of the faceplate from the top of the tankless water heater frame. This process exposes the inside of the tankless water heater.

In the next steps, you have to locate the single screw that was holding the air intake filter in place. Then first pull slightly towards, then slide the whole thing to the left and angle it slightly so it will slide over the motor without doing any damage. Then just turned the water spout and turned it on full blast and rinsed the heck out of the filter. Then used paper towels to dry it as best as possible and reinstalled the filter the same way you took it out.

Then replace your tankless water heater face plate and let the pump continue to run for 60-90 minutes. During this process, please don't plug your tankless water heater into the outlet until the flush procedure. 

  • Step 7: Rinse the tankless water heater after the vinegar treatment

After completing the 60 to 90 minutes vinegar circulation through the pump, you're ready to rinse the vinegar out from the tankless water heater. In the next process, you have to unplug the pump from the wall outlet and lift out the sump pump. Then allow it to drain into the vinegar bucket and place it aside of your space. Now put the empty bucket under your tankless water heater. Then unscrew the hose from cold water blue side only. After that replace the service valve cap and screw it. Then leave hot water hose. Next process is to open the lever that controls the cold water inflow and pass the water about 4 to 5 gallons through your tankless water heater.

Now open the output of hot water hose into the bucket. But make sure to close the cold water valve. When that is complete now, you need to check the water filters. To find out is there any water exit or not. If there is water existence, then unscrew with your finger and redirect them to your tankless water heater hose pipe on the blue side. After that remove the filters, make sure to inspect the debris. Thoroughly rinse filters with water and screw them again.

  • Final Step: Reattach everything and Turn on your water heater.

After completion of step number seven your tankless water heater and its air intake filter has been cleaned, now it's time to reassemble the whole water heater. After reassembly, please make sure to screw all service caps tightly before opening the valves.

When you are sure about that, everything perfectly capped tightly then you can start opening valves. Better to start the cold water valve first. After the start of a cold water heater valves, you will hear water rushing on your system. Next substep is to open the hot water valve. Then the gas and central circulation valve which color is yellow. Finally, you are allowed to plug in your tankless water heater. See carefully, on display to specific icons on the screen. If your power display shows everything right then the whole, the cleaning process completed, and you can use your water heater anytime.

Final words:

We hope that our researching tankless water heater flushing steps help you to clean your tankless water heater to give the best performance as like new one. There are many websites like or others to research how to flush tankless water heater? Hope our research is enough to do your job. Because these steps are suitable to clean all most any tankless water heater to get the better performance as like new one.

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