水有较硬之分。凡不含矿物质或含矿物质很少的水是软水。蒸馏水完全不含任伺矿物质，是绝对的软水。雨水出极少含矿物质，也是软水。河水通常是雨水汇集而成，含矿物质不多，也属于软水。矿泉水、井水，通常合矿物质都较多，所以是硬水。早在30多年前，美国科学家施罗德经过多 Water is harder. Where mineral or mineral-containing water is soft water. Distilled water is completely free of any mineral, it is absolutely soft water. Very little rain containing minerals, but also soft water. River water is usually collected from the rain, containing less minerals, also belong to the soft water. Mineral water, well water, usually with more minerals, it is hard water. As early as more than 30 years ago, the American scientist Schroeder passed more