Navien: tankless descaling and flushing, the maintenance manufacturers make a warranty condition

Every tankless manufacturer specifies periodic flushing of the heat exchanger, and most exclude lime damage from warranty. Rinnai's manual states that failure to flush will damage the heat exchanger and recommends at least annual flushing, more often with hard water. Metro Vancouver's water is very soft, around 2 to 25 mg/L hardness, which slows scale but does not remove the requirement or the value of checking the filter, trap and combustion at the same time.

A descaling visit circulates a manufacturer-approved solution through the heat exchanger via the isolation valves, cleans the cold-inlet screen, empties and checks the condensate trap and neutralizer, verifies combustion and venting, and resets the service reminder on units that have one. If the unit was installed without isolation valves, they are fitted first.