These systems each take the following filters: 2 of the Lead Reducing Carbon filters, part number 41400010 ( http://www.filtersfast.com/prodView.asp?idproduct=500 ) and 2 of the VOC Reducing Carbon filters, part number 41400011 ( http://www.filtersfast.com/prodView.asp?idproduct=499 ). You may also need to replace the o-rings depending on when you last changed them. The housing orings are the Hydrotech Housing O-ring 34201026 ( http://www.filtersfast.com/prodView.asp?idproduct=506 ) and the cartridge o-rings are the Hydrotech Aquafier Cartridge O-ring 34201010 ( http://www.filtersfast.com/prodView.asp?idproduct=505 ).