zeolite - A group of hydrated sodium aluminosilicates, either natural or synthetic, with ion exchange properties. (See gel zeolite, greensand.)
zeolite softening - The removal of calcium and magnesium by ion exchange using natural or synthetic zeolite. The term is sometimes used to refer to all ion exchange softening processes, even though organic ion exchange resins, not inorganic zeolites, are in most common use today.
zero soft - Water with a total hardness less than 1.0 grain per U.S. gallon, as calcium carbonate.
zone of aeration - The layer in the ground above an aquifer where the available voids are filled with air. Water falling on the ground percolates through this zone on its way to the aquifer.
zone of saturation - The layer in the ground in which all of the available voids are filled with water.
