We’ve done thousands of water filter changes and UV equipment service calls, and we’ve seen too many instances where homeowners buy those cheap carbon-cellulose filters. Essentially they are carbon powder impregnated onto filter paper. . .
Don’t use them! They are crap. UV sleeves get coated with a blackish film from them, and for close to the same price, they don’t last as long as other alternatives for odour reduction. Use coconut shell carbon block or coconut shell granular activated carbon filters. We use Pentek and Excelpure brands.
Depending on your water usage volume, the organics, sediment, and sulphur or H2S levels in your water (if you aerate to a cistern or use a Greensand filter), the type and size of prefiltration you are using — expect to change these out in a typical household anywhere from every 6 weeks to 3 months.