Zip MicroPurity Filters are independently certified to NSF performance standards. To maintain protection against contaminants, replace the filter at its rated capacity as performance declines beyond this point. It’s also essential to replace the filter every 12 months even if the rated capacity hasn't been reached, as the polyphosphate component is time-based and helps prevent limescale buildup in your HydroTap. For best performance, replace the filter at its rated capacity or every 12 months — whichever comes first.