The life of your pre-filter cartridge will depend largely on the source water being used. Drawing water out of the open ocean may allow your pre-filter cartridge last for several months, while drawing from polluted bays may foul your cartridge within hours of use. The cartridge is a 10″ x 2.5″ 5 micron pleated paper filter. (Please note it is very important to use a 5 micron filter with Rainman systems to protect the RO membranes and the high pressure pump.)