Many buyers confuse PP cotton, UDF and CTO filters in a 3-in-1 pre-filtration set. Each filter has its own unique function and cannot be replaced randomly.
PP Cotton Filter: The first stage of filtration. Mainly intercept sand, rust, sediment and large particle impurities. It is the most consumable part and needs regular replacement.
UDF Granular Activated Carbon: Second stage. Focus on absorbing residual chlorine, odor, organic pollutants and improving raw water smell.
CTO Compressed Activated Carbon: Third stage. With denser structure, it further filters tiny particles and residual chlorine, protecting the follow-up RO membrane.
Understanding the difference helps you choose the right filter combination for your local water quality. We provide standard and custom 10/20 inch filter cartridges, 3-in-1 sets and full 5-stage filtration kits for wholesale and OEM projects.