New media: straight talk about what zeolites will and won't do as a filter medium.(Tech Talk)

Zeolites, those minerals mined from natural sources or manmade products, have been around for a long time. Cat litter, the ion-exchangers in water softeners, green-sand filters for drinking water ... there are literally thousands of applications in our society.

A fairly recent appearance in the pool industry is a natural zeolite called clinoptilolite.

The most important apparent benefit of zeolites is their huge surface area for a given bulk volume. To understand how large that area is, compare the following: A cubic box measuring 1 foot on each side has an area of 6 square feet. Stack 27 navel oranges with 4-inch diameters into that box, arranged in three layers of nine each, and their surface area climbs to just under 10 square feet. Filter sand with a uniform grain diameter of 0.5 mm, and with a 40 percent void space, has approximately 2,200 square feet in that 1-cubic-foot box. Zeolites, on the other hand, have a square footage of more than 10 football fields in the same amount of space.

Some quick background: The zeolite clinoptilolite is a natural mineral. It is relatively soft on the Mohs hardness scale, ranging from 3 to 5. For a comparison, talc has a hardness of 1, silica quartz 7, and diamond 10. That means it is quite a bit softer than filter sand. In addition, most clinoptilolite is mined with lots of embedded fine clay, which must be removed before it can be used as filter medium. This requires long soaking and ...