Soft or Hard Water
Carbonates dissolved in water.
"Hard water" is water containing a quantity of dissolved minerals. Water hardness is a function of the amount of dissolved calcium and magnesium salts, iron and aluminum.
Total hardness can be calculated as
Total hardness in ppm Carbonate =
2.497 ppm Calcium
+ 4.115 ppm Magnesium
+ 1.792 ppm Iron
+ 1.822 ppm Manganese
The salts occur in a variety of forms where typically calcium and magnesium bicarbonates are referred to as "temporary hardness", and sulfates and chlorides are referred to as "permanent hardness".
When hard water is heated the carbonates precipitate out of solution, forming scale on the heat surfaces.
Soap is less effective and prevented from lathering in hard water because its reacts to form calcium or magnesium salt from the organic acids of the soap.
"Soft water" is treated water where the only cation (the positively charged ion) is sodium.
Water Hardness Classification1) | Milligrams per Liter (mg/L) | Grains per US Gallon (gpg) |
---|---|---|
Soft | 0 - 60 | 0 - 3.5 |
Moderate | 61 - 120 | 3.5 - 7 |
Hard | 121 - 180 | 7 - 10.5 |
Very Hard | > 180 | > 10.5 |
1) United States Geological Survey
- 1 mg/L = 1 ppm
- 1 ppm = 0.058 grains/US gallon
- 1 ppm = 0.07 Clark degrees
- 1 ppm = 0.1 French degrees
Hard water can be softened by passing it over an ion exchange resin.
- zeolite processes for home water softeners
- soda ash process for larger water softeners
Related Topics
-
Material Properties
Properties of gases, fluids and solids. Densities, specific heats, viscosities and more. -
Steam and Condensate
Design of steam & condensate systems with properties, capacities, sizing of pipe lines, system configuration and more.
Related Documents
-
Boiler Water - Total Dissolved Solids (TDS)
Impurities from the feedwater will concentrate in the boiling water. -
Domestic Water Supply - Lime Deposits
Lime deposited vs. temperature and water consumption. -
Ice and Water - Melting Points vs. Pressure
Online calculator, figures and tables with melting points of ice to water at pressures ranging from 0 to 29000 psia (0 to 2000 bara). Temperature given as °C, °F, K and °R. -
Oxygen - Solubility in Fresh and Sea Water vs. Temperature
Solubility of oxygen in equilibration with air in fresh water and seawater (salt water) - pressures ranging 1 - 4 bar abs. -
Parts per Million - ppm
ppm - or parts per million - is commonly used as a unit of concentration. -
Salinity of Water
Salinity - salt content - of fresh, brackish and sea water. -
Water - Thermophysical Properties
Thermal properties of water at different temperatures like density, freezing temperature, boiling temperature, latent heat of melting, latent heat of evaporation, critical temperature and more. -
Water - Thermophysical Properties
Thermal properties of water at different temperatures like density, freezing temperature, boiling temperature, latent heat of melting, latent heat of evaporation, critical temperature and more.