How can I properly flush a Rinnai tankless water heater to ensure optimal performance and longevity?

To properly flush a Rinnai tankless water heater for optimal performance and longevity, follow these steps:

1. Turn off the power and gas supply to the unit.
2. Connect a pump and hoses to the service valves.
3. Fill the system with a descaling solution and let it sit for the recommended time.
4. Flush the system with clean water until the water runs clear.
5. Remove the hoses and restore power and gas supply.
6. Check for any leaks and ensure the unit is functioning properly.