Dissolved silica is often mistaken for hardness staining but can be differentiated by some simple testing. Water conditioners do not remove silica.

Hardness is a function of the dissolved calcium and magnesium in the water and it is commonly expressed in milligrams/liter and grains/gallon. Hardness is typically treated with ion exchange (conventional water softening). Alternate anti-scalant systems can be used to reconfigure hardness and reduce precipitation in pipes and on fixtures, but they do not remove the hardness from the water.