Pond One Claritec 3000UV Pressurised Filter with 9w UVC Pond One Claritec 3000 Pressurised Filter is designed for a water pump to push water through it for filtration. All of these factors affect the end flow rate of the pump. As a guide, use the following calculations and match them to the head height values to cross reference end flow of the pump in l/ph. Head height refers to the height the pump must push water vertically to the filter however, other factors listed below also add to the ultimate head height values. For every 1m of pipe is equivalent to 10cm of head height. For every 1 size hose diameter reduced from the maximum outlet diameter of the pump is equivalent to 1m of head height. For every 90 degree bend in the hose is equivalent to 1m head height. For every 45 degree bend in the house is equivalent to 50cm of head height.