The K Pressure Filters are designed to allow the unrestricted flow of water through the unit, meaning that a lower wattage pump can be used. The filters use a blower to save water and clean more thoroughly during backwashing. The K media is re-engineered to offer excellent mechanical filtration and tremendous biological performance. All models feature a multi-port valve and a clear viewing dome for easy inspection. Rather than using conventional beads as its principle filter media, Evolution Aqua uses K media, which has a vast surface area that can effectively house beneficial bacteria. How this works is that water is pumped into the filter from the pond, through a multi-port valve where the internal pipework directs the water to the bottom of the unit. As the water flows upward, dirt and debris is trapped within the mass of filter media. The filtered water flow back into the pipework at the top of the unit, through the multi-port valve and back down the return line into the pond.