How can I flush the heat exchanger on my Takagi TK-110U-E unit?

Flushing the heat exchanger on your Takagi TK-110U-E tankless water heater is an essential maintenance task to ensure its efficiency and longevity. Over time, mineral deposits and sediment can accumulate inside the heat exchanger, reducing its performance. Flushing helps remove these deposits, allowing the unit to operate more efficiently. Here's a step-by-step guide on how to flush the heat exchanger:

Before you begin, make sure to turn off the electrical power to the water heater and close the gas shut-off valve to ensure your safety during the flushing process.
What You'll Need:
* A submersible pump
* Two 5-gallon buckets
* A hose with connectors
* A descaling solution (available at hardware stores or online)
* Wrenches or pliers
Safety goggles and gloves
Step 1: Prepare the Descaling Solution
* Follow the manufacturer's instructions to prepare the descaling solution. Typically, this involves mixing the solution with water in a bucket. Make sure to use a solution that is suitable for tankless water heaters and safe for your specific model.
Step 2: Disconnect Water Supply Lines
* Locate the water supply lines connected to the inlet and outlet ports of the water heater.
* Use wrenches or pliers to disconnect both the hot water (outlet) and cold water (inlet) supply lines. Be prepared for some water to spill out during this process.
Step 3: Set Up the Pump and Hose
* Place one of the 5-gallon buckets near the water heater and position the submersible pump inside it.
* Attach one end of the hose to the pump's outlet and place the other end inside the bucket.
* Fill the bucket with the descaling solution until the pump's intake is submerged.
Step 4: Connect the Pump to the Water Heater
* Locate the isolation valves on the inlet and outlet of the water heater.
* Use wrenches or pliers to connect the pump's hose to the inlet (cold water) isolation valve. Make sure it's tightly secured.
* Ensure that the other end of the hose is submerged in the descaling solution in the bucket.
Step 5: Activate the Pump and Flush
* Turn on the submersible pump to circulate the descaling solution through the heat exchanger.
* Let the solution circulate for a sufficient amount of time, usually 45 minutes to 1 hour. Refer to the descaling solution manufacturer's instructions for the recommended duration.
Step 6: Drain the Solution
* Once the flushing process is complete, turn off the submersible pump.
* Disconnect the hose from the cold water inlet isolation valve and place the end of the hose in the second 5-gallon bucket.
* Open the cold water inlet isolation valve to allow the descaling solution to flow out of the heat exchanger and into the bucket.
Step 7: Rinse the System
* Close the cold water inlet isolation valve and disconnect the hose.
* Reconnect the hot water (outlet) and cold water (inlet) supply lines that you previously disconnected.
Step 8: Restore Water Supply
* Turn on the cold water supply to the water heater.
* Check for any leaks at the connections and make sure everything is properly tightened.
Step 9: Flush with Clean Water
Fill the 5-gallon bucket with clean water.
* Reconnect the pump to the water heater's cold water inlet isolation valve.
* Turn on the pump to circulate clean water through the heat exchanger for a few minutes. This helps flush out any remaining descaling solution.
Step 10: Finish and Restore Power
* Turn off the submersible pump and disconnect it.
* Reconnect the pump to the cold water inlet isolation valve.
* Turn on the electrical power to the water heater.
Step 11: Check for Proper Operation
* Turn on a hot water tap to ensure that the water heater is functioning correctly. It may take a few moments for hot water to flow as the system refills.

Flushing the heat exchanger on your Takagi TK-110U-E tankless water heater is an important maintenance task that should be performed regularly to prevent mineral buildup and maintain the unit's efficiency. By following these steps and using a suitable descaling solution, you can help prolong the life of your tankless water heater and ensure it continues to provide hot water efficiently. If you're uncomfortable with the process or encounter any difficulties, it's a good idea to consult a qualified technician or plumber for assistance.