How to flush a Takagi tankless water heater?

How to flush a Takagi tankless water heater is important maintenance to remove scale and maintain efficiency, should be done yearly, with steps involving vinegar, pump, and hoses. Takagi tankless water heater, Japanese brand made by Takagi Industrial Co., requires flushing to prevent mineral buildup, with procedure. Steps to flush Takagi tankless water heater: first turn off power to unit, turn off gas, close hot and cold water isolation valves, connect hoses to service valves, hot and cold, place pump in bucket with 5 gallons white vinegar, connect cold hose to pump, hot hose to bucket, open service valves, run pump for 45 to 60 minutes circulating vinegar through heat exchanger to dissolve scale, then flush with clean water for 5 to 10 minutes, close service valves, disconnect hoses, open isolation valves, turn on power and gas, check for leaks. Materials needed include submersible pump, 5 gallon bucket, white vinegar 5 gallons, hoses. Takagi recommends flushing yearly, more often with hard water, with error code indicating scale. If not comfortable, hire plumber costing $100 to $200. So flushing Takagi involves vinegar circulation for 45 to 60 minutes to remove scale, with pump and hoses, yearly maintenance.