This pet water fountain features a quadruple filtration system that not only keeps the water fresh through circulation, but also removes impurities. The system includes: 1) A pre-filter grid that removes large impurities like pet hair, 2) High-density filter cotton that blocks sediment, rust, and other micro-particles, 3) Coconut shell-activated carbon that absorbs residual chlorine and other hazardous substances, and 4) Ion exchange resin that removes heavy metal ions and other harmful ions through a chemical process. This ensures that the water remains of high quality for your pets.