Methods and systems for purifying water are provided in which the treated water is softer than the influent water and is mildly corrosive or non-corrosive. In one embodiment, the influent water is treated using a membrane configured to soften the treated water relative to the influent water while leaving the treated water mildly corrosive or non-corrosive. In alternative embodiments, the influent water is treated using a membrane to generate the treated water. The treated water is mixed in a mixing device with a stream of untreated water such that the resulting stream of mixed water is softer than the influent water and is mildly corrosive or non-corrosive.