Salt-free soft water is water that has been softened without the use of sodium. Water is said to be soft when there are few ions of magnesium and calcium present in it. These ions are frequently removed by adding sodium to the water, a process that creates salty, soft water. People on a reduced sodium diet should not drink soft water that has been softened in this manner because the amount of sodium in the water can exceed the recommended daily intake of sodium. Other processes will create salt-free soft water.
There are a number of ways to create salt-free soft water. One method for decreasing the amount of calcium and magnesium ions in water is to add potassium ions. The introduction of positively charged potassium to a water supply allows an ion exchange to occur. Once this process is complete, the number of positively charged calcium and magnesium ions is significantly reduced and the water is said to be soft. This process does create the presence of a potassium based salt in the water, but this salt does not affect the body in the same way that a sodium based salt does.
In order to create water that is completely free from all salts, the water must be distilled. In this process, water is boiled and the steam is captured. Only pure water vapor rises when water is boiled because heavier elements, such as the elements that make water hard, require a higher temperature in order to evaporate. Catching the steam and then allowing it to cool and condense back into liquid water is a way to create truly salt-free soft water.
The main benefit of having salt-free soft water is that it can significantly decrease the amount of sodium in a person's diet. People who soften the water coming into their homes often use that water as drinking water, and some methods of softening water can add a significant amount of salt, which may make drinking the water dangerous for people who are supposed to limit their sodium intake.
Salt-free soft water is also preferred by many people because it leaves less residue on objects. The ions in hard water can build up on plumbing fixtures and the inside of pipes which can damage them over time. Soft water also does not leave a film on surfaces such as bathtubs, sinks and counters the way that hard water does.