Culligan 1000R Replacement Filter Information: The Culligan 1000R cartridge is an easy to replace filter. Twist-off the old filter and twist-on the new filter. No mess! The Culligan 1000R replacement water filter life is up to 6 months or 500 gallons. The water filter life also depends on the quality of your water and your water usage. The Culligan 750R can be instead of the Culligan 1000R. However, the Culligan 750R does NOT reduce as many contaminants as the Culligan 1000R. The Culligan 1000R water filter can be in place of the Pentek QC10-CBRR water filter. Water Filter Systems that use the Culligan 1000R Filter: Culligan SY-1000 Under Sink Water Filter System Culligan SY-1000S Under Sink Water Filter System Culligan RV-1000 RV Water Filter System Culligan IC-1000 Inline Water Filter System American Plumber DW600 The Culligan 1000R filter also fits the SY-750, SY-750S, IC-750, and RV-750 water filtration systems.