The first step is understanding the make-up of your water. Does your water come for a municipality or from a private well source? What’s in the water? Municipal water users receive an annual water quality report mandated by the EPA that reveals where your water comes from, what it is treated with and what impurities they found during sample testing.
There are tests can be done to determine what your specific needs are. On municipal water the test are fairly simple and are offered free of charge. For well water more comprehensive testing is needed and can be done for a reasonable charge to cover lab fees.