If either of the following situations occurs:
• The display shows that the remaining filter capacity is 0 liters and keeps flashing.
• You have used the filter cartridge for six months.
• The hollow fiber of the filter cartridge (visible through the cartridge window) has turned rust brown or dark gray). To help you determine when to replace the filter cartridge, there is a self-adhesive color-coded cartridge replacement indicator. If the color of the filter matches the rust brown or dark gray shown on the indicator, replace a new filter cartridge.
• The volume of purified water decrease substantially.
• The filtered water has an unpleasant smell or is still turbid after purification.