Laboratory tests show that Phoenix Gravity New Millennium Edition™ filter cartridges initially reduce fluoride in drinking water by up to 75.5%. However, carbon-based filter cartridges that reduce fluoride typically lose this ability fairly quickly. Therefore, Berkey PF-2® fluoride & arsenic filter cartridges can be used in combination with Phoenix Gravity New Millennium Edition™ filter cartridges to reduce fluoride for up to 3,750 liters or 1 year.