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.
These inexpensive cartridges are widely used and available throughout the world from water filtration retailers and hardware stores.
Please note it is very important to use a 5 micron filter with this system to protect the RO membranes and the high pressure pump.