How Often Should You Replace a Whole-House Water Filter?

Cartridge systems (the 4.5" by 20" multi-stage units from iSpring, Aquasana Rhino, or Pentair) need new cartridges every 6 to 12 months. Sediment cartridges go first, especially on well water. Carbon-block cartridges follow shortly after.

Tank-style catalytic carbon (SpringWell CF, SoftPro Carbon) lasts 6 to 10 years on city water before the media is exhausted. There is no annual cartridge cost. You replace the entire media bed at the end of its life.

Salt-based softener resin lasts 10 to 15 years on properly pre-filtered water. The thing you actually refill monthly is the salt in the brine tank, not the resin.

Salt-free TAC conditioners need a media bed swap every 5 to 6 years. They do not regenerate, so there is nothing to do between replacements.

UV lamps are replaced annually regardless of how the water looks. Output drops below the certified disinfection dose long before the lamp visibly burns out.

Reverse osmosis units have three or four filters on different schedules: pre-filters every 6 to 12 months, post-carbon every 12 months, and the RO membrane itself every 2 to 4 years.