You should visit the heater at least once every three months.
Clean filter rinnai gas heater.
5 steps to cleaning your rinnai tankless water heater filter learn best practices on cleaning your filter from our youtube video learn more.
Use 4 gallons 15 1 liters of undiluted white vinegar to clean your tankless water heater.
Never use chemical solutions of any kind.
Know that a tankless water is not a set it and forget it water heater.
The rinnai is typical.