Anion – A negatively charged ion in solution such as bicarbonate, chloride or sulfate.

Anion Exchange – An ion exchanges process in which anions in solution are exchanged for other anions from an ion exchange.  In demineralization, for example, bicarbonate, chloride and sulfate anions are removed from solution in exchange for a chemically equivalent number of hydroxide anions from the anion exchange resin.

Attrition – The process in which solids are worn down or ground down by friction, often between particles of the same material.  Filter media and ion exchange materials are subject to attrition during backwashing, regeneration and service.

Backwash – The process in which beds of filter or ion exchange media re subjected to flow opposite to service flow direction to loosen the bed and to flush suspended matter collected during the service run to waste.

Brine (Softening) – A strong solution of salt(s), such as sodium chloride, and water used in the regeneration of ion exchange water softeners but also applied to the mixed sodium, calcium and magnesium chloride waste solution from regeneration.

Calcium (Ca) – One of the principal elements making up the earth’s crust, the compounds of which when dissolved, make the water hard.  The presence of calcium in water is a factor contributing to the formation of scale and insoluable soap curds which are a means of clearly identifying hard water.

Capacity – An expression of the quantity of an undesirable material which can be removed by a water conditioner between servicing of the media (i.e. cleaning regeneration or replacement, as determined under standard test conditions).  For ion exchange water softeners, the capacity is expressed in grains of hardness removal between successive regenerations and is related to the pounds of salt used in regeneration.  For filters, the capacity may be expressed in the length of time or total gallons delivered between servicing.