It can be difficult to decide which method for softening hard water is best because there are a number of choices available. Cost of a water softener system from $400 to $1,200 -- can be a factor, as well as how the water softener unit is set up, its size, and how much water it will soften before requiring maintenance.

Household water can be tested using a water test kit from a pool supplier or a water softener vendor. Water hardness is measured in grains per gallon (GPG), parts per million (PPM), or milligrams per liter (MG/L). Water that measures from 3.5 to 7 GPG is considered hard water.

Ionic exchange water softeners consist of a brine tank, a filtering unit, valves to direct the flow of the water and a meter or timer to indicate when the filter needs to be recharged. Recharge cycles can be set to occur at certain times, based on water demand for the household, or it can be done manually. There are also semi-automatic systems, which let the user know when the softener needs recharging.

Ionic exchange water softeners work by replacing ions of the minerals that cause hardness, calcium and magnesium, with sodium or potassium ions. This occurs when water is filtered through negatively charged plastic beads, which have been soaked in brine. The magnesium or calcium ions are attracted to the negatively charged beads, which are flushed with brine, driving off the calcium or magnesium ions and replacing them with sodium ions. Finally, the water containing the hard ions is discarded.

Using ionic exchange water softeners poses no health risks for most people. But those who are on sodium-restricted diets should either keep bottled or non-treated, filtered water on hand for cooking and consumption or use potassium chloride instead of sodium chloride to soften their water. It should be noted that potassium chloride is more expensive than sodium chloride.