The image above shows heaters working under hard water conditions in combination with soap based detergents.
How do I know if I have hard water?
Hardness can be recognised by the need for more soap to form a lather. The amount of Calcium (Ca) and Magnesium (Mg) ions in the water determines its hardness. Hard water reduces the soap detergent's washing capability due to the Calcium and Magnesium precipitating fatty acids in the soap. The precipitate is called "soap scum" and mainly consists of Calcium Stearate, a white waxy powder.
What causes hard water?
As a solvent, water easily absorbs impurities and minerals when it moves through rock and soil before it gets to your tap. Underground water is often hard, especially water from chalk or limestone layers. When combined with carbon dioxide, it forms very weak carbonic acid and water becomes resultantly better solvent. Two of the most common minerals that dissolve easily in water, calcium and magnesium, can make water hard. The degree of hardness of water increases as the amount of calcium and magnesium dissolved in water increase.
What is temporary and permanent hardness?
Distinction is made between temporary hardness and permanent hardness. Temporary hardness is precipitated by heating and cooking and forms deposits, called scaling, in pans, plumbing, boilers, washing machines and other appliances.
Permanent hardness is caused primarily by Calcium Sulphate (CaSO4) and Magnesium Sulphate (MgSO4) or Calcium Chloride (CaCl2) and Magnesium Chloride (MgCl). This type of hardness is not precipitated by boiling.
Extremely hard water can be harmful for a home's plumbing system and many opt to add a treatment plan to soften the water.
What kinds of detergents should I use with hard water?
Soap based detergents should not be used under permanent hard water conditions. Synthetic detergents are a better choice since they don't add to the scaling problem.