Difference Between Soft Water and Hard Water

Water is classified as soft water or hard water. Water containing little or no calcium and magnesium ions is called soft water, while water containing a large amount of these ions is called hard water. Total Dissolved Solids (TDS) measures the total concentration of all ions in water, usually expressed in ppm. Water hardness refers to the concentration of calcium and magnesium ions in the water; the unit of hardness is ppm, and 1 ppm represents 1 milligram of calcium carbonate per liter (mg/L).

Water hardness is caused by sodium bicarbonate or magnesium bicarbonate, resulting in temporary hard water (boiling temporary hard water decomposes the sodium bicarbonate, forming insoluble carbonates that precipitate, turning the water from hard to soft). Hardness is caused by calcium and magnesium sulfates or chlorides, resulting in permanent hard water. Based on the total hardness value, water with a total hardness of 0-30 ppm is considered soft water, and a total hardness above 60 ppm is considered hard water. High-quality drinking water has a total hardness of no more than 25 ppm, and high-quality soft water has a total hardness below 10 ppm. In natural water sources, rainwater and snowmelt from unpolluted areas far from cities are considered soft water; spring water, stream water, river water, and reservoir water are mostly temporarily hard water, and some groundwater is high-hardness water.

For over a century, science and technology have greatly promoted modern industry, leading to severe pollution. Water is no longer the kind of water that was generally drinkable hundreds of years ago. While the rapid development of modern industry has gradually improved human living conditions, ubiquitous chemical technologies and industrial pollution have severely disrupted the Earth's environmental balance, causing water resources to suffer from severe pollution. Water now contains many suspended solids, colloids, and harmful heavy metal ions such as calcium and magnesium, as well as bacteria. Since over 95% of household water consumption is for non-potable purposes, poor-quality water not only harms human health but also damages water-related daily life and household appliances.

Water Hardness Unit Conversion