Manufacturers of tankless water heaters recommend you perform regular cleaning and maintenance, and flushing of your tankless water heater if necessary. Due to hard water, your tankless water heater may develop lime and mineral deposits on heater’s elements. Sediment build-up is particularly dangerous in narrow water passages as it might clog the element and prevent further normal heating operation.
One of the most important elements is the heat exchanger, which has those narrow water passages. Flushing tankless water heaters whose heat exchangers are blocked by the lime scale is very important and must be done before something bad happens.
If you don’t flush the your tankless water heater, the heat exchanger can be damaged as not enough water will pass through and cool it down. Any damage which is related to lime scale build-up is not covered by the warranty.