www.WaterCoolerFilters.co.uk sell two different water filters: Pentek One Micron Water Cooler Filter and Brita 
0.5 Micron Water Cooler Filter.
The Pentek One Micron Water Cooler Filter provides the customer with one micron replacement filter which can be easily replaced by every customer. The EPDWA recommend that each filter on a water cooler should be changed every six months to ensure maintenance of the integrity of the water cooler.
The Brita 0.5 Micron Water Cooler Filter provide a much greater level of filtration. Full details on the Brita Water cooler filters can be found in a separate blog.
