The simple definition of water hardness is the amount of dissolved calcium and magnesium in the water.
Generally we measure hardness as ppm or mg/l of CaCO3 (Calcium Carbonate).
0 – 60 mg/l is regarded as soft for most purposes (Some processes require far lower)
61 – 120 mg/l is moderately hard
121 – 180 mg/l is hard
Greater than 180 is very hard
Water in the atmosphere picks up CO2, creating a weak carbonic acid (H2CO3), as this water falls as rain and percolates down through the rock strata, it dissolves rocks containing calcium and magnesium
Hard water is high in dissolved minerals, both calcium and magnesium, and other elements such as carbonate, chloride and sulphate which affect the type of hardness
Drinking Hard water has no adverse health effects, and the National Research Council (National Academy of Sciences) states that hard drinking water generally contributes a small amount toward total calcium and magnesium human dietary need
Many industrial and domestic water users are concerned about the hardness of their water. When hard water is heated, such as in a boiler or kettle, solid deposits of calcium carbonate can form. This scale can reduce the life of equipment, raise the costs of heating water and lower the efficiency of the boiler.
Hardness can also affect other water treatment equipment, like Reverse Osmosis units, and clogs feed pipes.
Total Hardness –
Total hardness is measured as CaCO3 and is the combined measurement of the hardness causing elements in the water.
Otherwise known as Bi-carbonate hardness or Alkalinity hardness. Temporary hardness is that caused by calcium and magnesium in conjunction with bicarbonate. It can be removed by boiling the water, this drives off some of the CO2, allowing calcium and magnesium carbonate to precipitate out. The water is left softer (because some of the hardness is left behind) but still contains the permanent hardness elements.
This is the Sulphate and Chloride Hardness. Boiling the water has no effect on precipitating the hardness out. This wont scale the boiler or pipes, but can cause an issue called ‘foaming’ in boilers, which causes carryover of contaminants into the steam.