If your water is hard, you can get a lime or calcium buildup in your tankless water heater. To clean it out and flush the system, shut off all of the inlets and outlets to your heater, turn off the power and release the water inside of the unit. Then, fill a 5 gallon bucket with 2-3 gallons of white vinegar and a gallon of water. Connect a sump pump to the outlet of the heater and place it into the bucket, allowing the vinegar/water mixture to cycle for approximately 45 minutes. This should remove the majority of the buildup and allow your tankless heater to run like new again.
Tankless water heaters can be found at www.supplyhouse.com
