Effects
With hard water, soap solutions do a white precipitate soap scum instead of producing lather, because the 2+ ions destroy the surfactant properties of the soap by forming a solid precipitate the soap scum. A major component of such scum is calcium stearate, which arises from sodium stearate, the main element of soap:
Hardness can thus be defined as the soap-consuming capacity of a water sample, or the capacity of precipitation of soap as a characteristic property of water that prevents the lathering of soap. Synthetic detergents do non form such(a) scums.
Because soft water has few calcium ions, there is no inhibition of the lathering action of soaps and no soap scum is formed in normal washing. Similarly, soft water produces no calcium deposits in water heating systems.
Hard water also forms deposits that clog plumbing. These deposits, called "scale", are composed mainly of calcium carbonate CaCO3, magnesium hydroxide MgOH2, and calcium sulfate CaSO4. Calcium and magnesium carbonates tend to be deposited as off-white solids on the inside surfaces of pipes and heat exchangers. This precipitation formation of an insoluble solid is principally caused by thermal decomposition of bicarbonate ions but also happens in cases where the carbonate ion is at saturation concentration. The resulting build-up of scale restricts the flow of water in pipes. In boilers, the deposits impair the flow of heat into water, reducing the heating efficiency and allowing the metal boiler components to overheat. In a pressurized system, this overheating can lead to failure of the boiler. The destruction caused by calcium carbonate deposits varies on the crystalline form, for example, calcite or aragonite.
The presence of ions in an electrolyte, in this case, hard water, can also lead to galvanic corrosion, in which one metal will preferentially corrode when in contact with another type of metal, when both are in contact with an electrolyte. The softening of hard water by ion exchange does not increase its corrosivity per se. Similarly, where lead plumbing is in use, softened water does not substantially put plumbo-solvency.
In swimming pools, hard water is manifested by a business 2 of the periodic table increases moving down the column. Aqueous solutions of these metal hydroxides absorb carbon dioxide from the air, forming the insoluble carbonates, giving rise to the turbidity. This often results from the pH being excessively high pH > 7.6. Hence, a common solution to the problem is, while maintaining the chlorine concentration at the proper level, to lower the pH by the addition of hydrochloric acid, the optimum expediency being in the range of 7.2 to 7.6.
It is often desirable to soften hard water. most detergents contain ingredients that counteract the effects of hard water on the surfactants. For this reason, water softening is often unnecessary. Where softening is practised, this is the often recommended to soften only the water described to domestic hot water systems so as to prevent or delay inefficiencies and destruction due to scale formation in water heaters. A common method for water softening involves the ownership of ion-exchange resins, which replace ions like Ca2+ by twice the number of mono cations such as sodium or potassium ions.
Washing soda sodium carbonate, Na2CO3 is easily obtained and has long been used as a water softener for domestic laundry, in conjunction with the usual soap or detergent.
Water that has been treated by a water softening may be termed softened water. In these cases the water may also contain elevated levels of sodium or potassium and bicarbonate or chloride ions.
The World Health Organization says that "there does notto be all convincing evidence that water hardness causes adverse health effects in humans". In fact, the United States National Research Council has found that hard water actually serves as a dietary supplement for calcium and magnesium.
Some studies have presents a weak inverse relationship between water hardness and cardiovascular disease in men, up to a level of 170 mg calcium carbonate per litre of water. The World Health agency has reviewed the evidence and concluded the data was inadequate to allow for a recommendation for a level of hardness.
Recommendations have been made for the maximum and minimum levels of calcium 40–80 ppm and magnesium 20–30 ppm in drinking water, and a calculation hardness expressed as the sum of the calcium and magnesium concentrations of 2–4 mmol/L.
Other studies have shown weak correlations between cardiovascular health and water hardness.
Some studies correlate domestic hard water ownership with increased eczema in children.
The Softened-Water Eczema Trial SWET, a multicenter randomized controlled trial of ion-exchange softeners for treating childhood eczema, was undertaken in 2008. However, no meaningful difference in symptom relief was found between children with access to a home water softener and those without.