Quick take
RKIN currently recommends replacing RC-QT-PAC every 6–12 months as needed. The current individual prefilter listing is about $44.86.
What RC-QT-PAC does
It is the U1 first/second-stage combined sediment and carbon prefilter, protecting the downstream RO membrane.
Replacement interval
RKIN publishes a 6–12 month interval, with faster replacement appropriate for dirtier source water.
Current price
RKIN’s current U1 replacement-filter collection lists the prefilter around $44.86.
Do not reset without replacing
A filter-life alert should reflect actual cartridge replacement; resetting an exhausted prefilter does not restore protection for the RO membrane.