How do I flush the heat exchanger on a Takagi TK-110U-E unit?

Flushing the heat exchanger on a Takagi TK-110U-E tankless water heater is an essential maintenance task that helps remove mineral deposits and debris that can accumulate over time. Flushing the heat exchanger improves the unit's efficiency and prolongs its lifespan. Here are step-by-step instructions on how to flush the heat exchanger:

Important Safety Precautions:
Before you begin the flushing process, it's crucial to follow these safety precautions:
* Turn Off the Power and Gas Supply: Locate the circuit breaker or disconnect switch for the water heater and turn it off to cut the power supply. Also, shut off the gas supply to the unit.
* Allow the Unit to Cool: Ensure that the unit has cooled down sufficiently before starting the flushing process to avoid burns.
* Gather the Necessary Tools and Materials: You will need a submersible pump, a bucket or container, a hose, and white vinegar or a commercial descaling solution. Make sure the hose and pump are suitable for use with a tankless water heater.
Flushing Process:
1. Prepare the Vinegar or Descaling Solution:
If you're using white vinegar, mix it with an equal amount of water to create a 1:1 vinegar-water solution. If you prefer a commercial descaling solution, follow the manufacturer's instructions for dilution.
2. Locate the Service Valves:
On the Takagi TK-110U-E unit, you should find service valves on the cold water inlet and hot water outlet pipes. These valves allow you to isolate the unit for maintenance.
3. Connect the Hose:
Connect one end of the hose to the outlet side of the submersible pump. Make sure the hose is securely attached.
4. Submerge the Pump:
Place the submersible pump into a bucket or container filled with the vinegar or descaling solution. Ensure the pump is fully submerged.
5. Connect the Other End of the Hose:
Attach the other end of the hose to the cold water inlet service valve on the Takagi TK-110U-E unit. Make sure the connection is secure.
6. Open the Hot Water Tap:
Open a hot water tap or fixture connected to the Takagi unit. This step allows air to enter the system and helps with the flushing process.
7. Turn On the Pump:
Turn on the submersible pump to begin circulating the descaling solution through the unit. The solution will flow through the heat exchanger, loosening and dissolving mineral deposits.
8. Let the Solution Circulate:
Allow the descaling solution to circulate through the system for about 45-60 minutes. During this time, you may notice that the solution coming out of the hot water tap is discolored. This is a sign that it's working to remove scale and debris.
9. Flush with Fresh Water:
After the descaling solution has circulated for the recommended time, turn off the submersible pump and close the hot water tap. Disconnect the hose from the cold water inlet service valve.
10. Rinse with Fresh Water:
Connect the hose directly to the cold water inlet service valve again. Open the hot water tap and allow clean, fresh water to flow through the system for at least 15-20 minutes. This rinses out any remaining descaling solution and loosened deposits.
11. Turn Off the Hot Water Tap and Pump:
Once you've completed the rinsing process, close the hot water tap and turn off the submersible pump.
12. Disconnect the Hose:
Remove the hose from the cold water inlet service valve.
13. Restore Power and Gas Supply:
Turn the circuit breaker or disconnect switch back on to restore power to the Takagi TK-110U-E unit. Also, turn on the gas supply.
14. Check for Leaks and Test the Unit:
Inspect all connections for leaks, and address any issues if necessary. Finally, test the unit to ensure it is operating correctly and providing hot water as expected.

Flushing the heat exchanger on your Takagi TK-110U-E tankless water heater should be done periodically, especially if you live in an area with hard water. The frequency of flushing may vary depending on water quality and usage patterns. Regular maintenance, including heat exchanger flushing, helps maintain the efficiency and longevity of your tankless water heater.