The System 3 Modular Diatomaceous Earth (D.E). Filters deliver high quality D.E. filtration. Diatomaceous earth, a natural substance, is so fine, it traps dirt and debris as small as five microns (1/10 the width of a human hair). That means body oils, suntan lotions, pollens, dust, and even some bacteria are trapped in the filter, leaving behind sparkling clear, healthier water. Thanks to a simple, one-piece module design the System 3 Modular D.E. filter is easier to clean than grid designs. Combined with a unique balanced-flow tank design which maximizes the use of the module's surface area, this filter is able to trap more dirt and reduce the frequency of cleaning. The System 3 Modular D.E. filter is also an eco-friendly choice for your pool. Water flows very efficiently through the modular D.E. filters allowing the use of smaller pumps or lower pump speeds to minimize energy use. And when consumers rinse rather than backwash, they can significantly reduce water use, too.