The surface of Earth is composed of 2/3 of water, which only 1% is drinking water partly polluted. Filtering and cleaning the water are time consuming. Then we need always to spend more and more money for water. Scaling, limestone, rust and microbiological deposits in water pipes make expensive maintenance, cleaning and energy, and above all endanger our health. 

1. What is limestone/scaling ?

Limestone is a sedimentary rock characterised by a high calcium mineralisation. Limestone is formed in two ways. It can be formed with the help of living organisms and by evaporation.

Calcium, scaling and limestone are almost the same thing.

Chemically limestone is mainly calcium carbonate (CaCO3): a mix of the calcium ion (Ca++) and the carbonate or carbone oxide (CO3--). Limestone is formed (scaling) when water containing particles of calcium carbonate evaporate, leaving behind the sediment deposit. The water pressure compacts the sediment, creating limestone.

The color of the limestone depends on the other sediments in the mixture besides the mineral calcite, which is white; impurities such as sand, clay, and organic material are also present in limestone and affect the color.

Sulfates contained in the water come from the dissolution of gypsum. Gypsum is a hydrated calcium sulphate which is slightly soluble (7g/L in normal conditions). The authorised limit value of sulfates in drinking water is 250mg/L. Beyond the water is not drinkable.

2. Limestone and water hardness :

The simple definition of water hardness is the amount of dissolved calcium and magnesium in the water. Hard water is high in dissolved minerals, both calcium and magnesium. The water hardness is defined as the total hardness (TH) which primarily corresponds to calcium and magnesium salts. More the water is rich in calcium (limestone) and magnesium, more it is called "hard". Conversely a poor water in limestone is called "soft".

Hardness is caused by compounds of mainly calcium and magnesium, and by a variety of other metals: iron, aluminium, and manganese can also be present at elevated levels in some locations. General guidelines for classification of waters are: 0 to 60 mg/L (milligrams per liter) as calcium carbonate is classified as soft; 61 to 120 mg/L as moderately hard; 121 to 180 mg/L as hard; and more than 180 mg/L as very hard.

The water hardness is expressed by an index, or total hardness, TH, in degrees, each degree determined by the following formula:

1 degree (°F : French unit) = 4 mg/liter of calcium or 2.43 mg/liter of magnesium or 10 mg of limestone.

The waters are classified according to their TH (French TH)

0 to 6 degrees              very soft water

6 to 15 degrees             soft water

15 to 25 degrees           moderately hard water

25 to 35 degrees          hard water

> 35 degrees                 very hard water

Water hardness can be expressed in various units, such as degrees of general hardness (dGH), German degrees (°dH), parts per million (ppm, mg/L, or American degrees), grains per gallon (gpg), English degrees (°e, e, or °Clark), or French degrees (°fH, °f or °F; lowercase f is used to prevent confusion with degrees Fahrenheit). The table below shows conversion factors between the various units. 

It is easy to detect, without testing, the hardness of your water :

With soft water (rain water), soap makes quickly foam and it is hard to get rid of the soap.

On the other hand, hard water (limestone) quickly removes soap and even gives hands a little rough after washing. But it needs more soap to wash or clean.

You may have felt the effects of hard water, literally, the last time you washed your hands. Depending on the hardness of your water, after using soap to wash you may have felt like there was a film of residue left on your hands. In hard water, soap reacts with the calcium (which is relatively high in hard water) to form "soap scum". When using hard water, more soap or detergent is needed to get things clean, be it your hands, hair, or your laundry.

- Beneficial to health : hard drinking water (rich in calcium and in magnésium) generally contributes a small amount toward total calcium and magnesium human dietary needs. Some studies suggest a correlation between hard water and lower cardiovascular disease mortality. Hard drinking water is also more drinkable. Hard drinking water is high in mineral salts, especially calcium and magnesium ions. These natural minerals give the water a crisp, pleasant and fresh taste. Furthermore a carbonated water generates a coated deposit on the pipes, which provides a protection against the corrosion.

- On the other hand hard drinking water has many domestic drawbacks : minerals that cause hard water have a wide impact on households. In the home hard water can lead to the furring and scaling of heating systems, kettles and household appliances such as washing machines. Clothes laundered in hard water may look dingy and feel harsh and scratchy. Dishes and glasses washed in hard water may become spotted as they dry. Hard water may cause a film on glass shower doors, shower walls, and bathtubs. Hair washed in hard water may feel sticky and look dull. Hard water creates white deposits (limestone) inside the pipes and also outside the pipes at the joints. 

This is why limestone is, after the taste, the second ground of not drinking tap water.

These disadvantages increase especially with heated water. Indeed the rate of limestone deposits increases with the temperature. When hard water is heated, such as in a home water heater, solid deposits (scale) of calcium carbonate (limestone) can form. This scale can reduce the life of equipment, raise the costs of heating the water, lower the efficiency of electric water heaters, and clog pipes. Mineral buildup may occur in our home coffee maker. Accumulated scale is a poor conductor of heat. In water heaters, accumulated scale insulates the water from the heat source. Water heaters with scale buildup used more energy to deliver a given amount of hot water than heaters without scale buildup (3mm scale need 30% more electricity).

On the opposite soft water (no limestone) has also some drawbacks :

-Soft water prevents protective carbonated deposits on the pipes and increases the corrosion of pipes and equipments. The water becomes aggressive.

-The corrosion, also related to the pH (acidity) of water, can also cause the solubilisation of metals : particularly iron, copper and lead, which creates metallic sludge and mud in the water (closed circuit) as the central heating or tower cooling or a heat pump.

To know the status of drinking water in France

http://www.sante.gouv.fr/qualite-de-l-eau-potable

Everybody uses water. All the industrial domains use water. Most of waters contain some limestone except river water and rain water that are usually polluted and full of microorganisms.

4. Diseases, contamination, bacteria and our Health :

Water is also a vector of microbial, bacterial (legionella, ...) and viral contamination. Water is a container of food or organic materials, biofilm, microorganisms and algae which interfere dramatically our health.