Hard and Soft Water: Types, Examples, Differences

Hard and Soft Water: We all know that water is transparent, but did you realise that even clear water contains dissolved minerals and chemicals? The white scale that develops in sinks and faucets is caused by minerals dissolved in water. The concentration of specific minerals determines the “hardness” of water. Water that lacks these minerals is known as “soft” water. Let’s take a closer look at the two types of water and their pros and downsides.

What is Hard Water?

Rainwater is naturally soft. However, as it moves through the ground and percolates through deposits of limestone, gypsum, or chalk, it tends to end up with higher concentrations of calcium and magnesium compounds, causing it to become hard water. 

Hence, hard water is the excessive presence of calcium and magnesium compounds in water. The higher the amount of these minerals present in water, the higher it will rank on the hardness scale. While both the minerals are essential to everyday health, calcium and magnesium do not help deal with household waterworks.

Depending on the type of salts present in water, the hardness of water can be divided into two types. These are:

Temporary Hardness of Water

The presence of magnesium and calcium bicarbonates make water temporarily hard. In this case, the hardness in water can be removed by boiling.

While boiling, the soluble salts of \(\mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2}\) is converted to insoluble carbonates \(\mathrm{MgCO}_{3}\). This gets precipitated and is subsequently removed. After filtration, the water we get is soft water.

Permanent Hardness of Water

The presence of magnesium and calcium chlorides, and sulphides in water, make water permanently hard. It is called permanent because this hardness cannot be removed by boiling.

The hardness of water is removed by treating the water with washing soda. Sulphide and chloride salts of magnesium and calcium present in Hard water form insoluble carbonates with washing soda. Thus, hard water is converted to soft water.

What is Soft water?

Unlike hard water, soft water is of harsh minerals and has a low, negligible, or zero concentration of calcium or magnesium salts. It is the surface water derived from impervious, calcium-poor river basins, or is groundwater derived from igneous/sedimentary rocks which are low in mineral content. 

The Noticeable Signs of Hard Water vs. Soft Water

Distinct signs of the hardness of water are observed in and around our homes; the absence of these signs would mean that the water is soft.

Signs of Hard Water Include

1. Feeling a film on hands after washing them: Soap reacts with calcium and magnesium salts to form soap scum. To remove soap scum, hands need to be rinsed for a longer time. Soaps do not form lather with hard water.
2. White Spots: Glasses, silverware or utensils cleaned with hard water contain visible white spots. Faucets and sinks also contain these spots. These spots are usually deposits of calcium carbonate.
3. Mineral stains. Clothes washed with hard water show up mineral stains and can wear out faster due to the harshness of hard water.
4. Less water pressure in your home. Hard water can form deposits on plumbing fixtures that are white and chalky in appearance. This results in shrinking the interior diameter of the pipes and reducing water flow.

Signs of Soft Water Include

1. When washing clothes and dishes with soap, a healthy lather is visible.
2. After each wash, your hair and skin will be softer and silkier.
3. There are no mineral stains on the garments, and they appear to be cleaner.
4. In your home, you should have good water pressure.
5. A mild salt flavour in drinking water, while the difference in taste is sometimes negligible. 
6. Scale buildup is not found in appliances and pipes.

Water Treatments to Achieve Hard Water or Soft Water

The hardness of water can be increased or decreased by some artificial methods. These treatments are known as “water softeners” and “water hardeners.”

Removing Temporary Hardness of Water

There are many methods through which we can remove the temporary hardness of the water and they are explained below:

By Boiling

Hard water containing soluble bicarbonates are converted into insoluble carbonates, which are removed by filtration.

\(\mathrm{Ca}\left(\mathrm{HCO}_{3}\right)_{2} \rightarrow \mathrm{CaCO}_{3} \downarrow+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2}\)

\(\mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2} \rightarrow \mathrm{MgCO}_{3} \downarrow+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2}\)

By Clark’s Method

Calcium hydroxide removes the hardness of water by converting bicarbonates into carbonate. 

Reaction: \(\mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{Ca}\left(\mathrm{HCO}_{3}\right)_{2} \rightarrow 2 \mathrm{CaCO}_{3} \downarrow+\mathrm{H}_{2} \mathrm{O}\)

Removing Permanent Hardness of Water

We can remove the permanent hardness of water with the help of the following methods:

Gan’s Permutit Method

In this method, sodium aluminium ortho silicate known as permutit or zeolite is used to remove the permanent hardness of the water.

\({\rm{N}}{{\rm{a}}_2}{\rm{A}}{{\rm{l}}_2}{\rm{S}}{{\rm{i}}_2}{{\rm{O}}_8}.{\rm{x}}{{\rm{H}}_2}{\rm{O}} + {\rm{C}}{{\rm{a}}^{2 + }} \to 2{\rm{N}}{{\rm{a}}^ + } + {\rm{CaA}}{{\rm{l}}_2}{\rm{S}}{{\rm{i}}_2}{{\rm{O}}_8}. {\rm{x}}{{\rm{H}}_2}{\rm{O}}\)

Calgon’s Process

In this method, sodium-hexa-metaphosphate \(\left(\mathrm{NaP} \mathrm{O}_{3}\right)_{6}\) known as Calgon is used. The hardness in water is removed by the adsorption of \(\mathrm{Ca}^{2+}\) and \(\mathrm{Mg}^{2+}\) ions.

Ion Exchange Resin Method

Ion-exchange or Deionization, or Demineralisation, is a process by which ions present in an insoluble solid are exchanged for ions in solution when brought in contact with each other.

Ion-exchange Resin – It is a crosslinked network of an organic polymer having some ionisable group. It may be of two types depending upon the nature of the ionisable group.

(i) Cation Exchange Resin or Cation Exchanger – Such resins have – \(\mathrm{SO}_{3} \mathrm{H},-\mathrm{COOH}\) or \(-\mathrm{OH}\) (phenolic) group as the ionisable group. These resins exchange the cationic portion of insoluble minerals by their hydrogen atom and are known as cation exchangers.

(ii) Anion Exchange Resin or Anion Exchanger – These resins have \(-\mathrm{NH}_{2},-\mathrm{NHCH}_{3},-\mathrm{N}\left(\mathrm{CH}_{3}\right)_{2}\) or \(-\text {OH}\) group. These resins exchange the anionic portion of the minerals, and they are known as an anion exchanger.

Hard water is converted into soft water by making use of ion-exchange resins. Hard water is initially passed through the cation exchange column, where all the cations (like \(\mathrm{Ca}^{2+}\), \(\text {Mg}^{2+}\) etc.) are absorbed by the resin and an equivalent amount of \(\text {H}^{+}\) ions are released from this column to water.
Thus,

\(2{\text{RH}} + {\text{C}}{{\text{a}}^{2 + }} \to {{\text{R}}_2}{\text{Ca}} + 2{{\text{H}}^ + }\)

\(2{\text{RH}} + {\text{M}}{{\text{g}}^{2 + }} \to {{\text{R}}_2}{\text{Mg}} + 2{{\text{H}}^ + }\)

From the cation exchanger, hard water is passed through an anion exchange column. Here, the resin removes all the anions (like \(\text {SO}_{4}^{2-}, \text {Cl}^{-}\) etc.) from the mineral and an equivalent amount of \(\text {OH}^{-}\) ions are released from this column to water. Thus,

\(\mathrm{R}^{\prime} \mathrm{OH}+\mathrm{Cl}^{-} \rightarrow \mathrm{R}^{\prime} \mathrm{Cl}+\mathrm{OH}^{-}\)

\(2 \mathrm{R}^{\prime} \mathrm{OH}+\mathrm{SO}_{4}^{2-} \rightarrow \mathrm{R}_{2}^{\prime} \mathrm{SO}_{4}+2 \mathrm{OH}^{-}\)

\(2 \mathrm{R}^{\prime} \mathrm{OH}+\mathrm{CO}_{3}^{2-} \rightarrow \mathrm{R}_{2}^{\prime} \mathrm{CO}_{3}+2 \mathrm{OH}^{-}\)

and \(\text {OH}^{-}\) ions get combined to produce water molecule

\(\mathrm{H}^{+}+\mathrm{OH}^{-} \rightarrow \mathrm{H}_{2} \mathrm{O}\)

The water coming out from the exchanger is from cations as well as anions. Ion-water is known as deionised or demineralised water.

Advantages of Hard and Soft Water

The advantages of hard and soft water are explained below:

Hard Water Pros

Tastes Better: Hard water has a better taste than soft water. Soft water is tasteless. 

Strengthens Bone & Teeth: Our bones and teeth are primarily built from calcium. Hard water rich in calcium and magnesium minerals acts as a dietary supplement for both. As a result, the consumption of hard water strengthens your bones and teeth.

Maintains Digestive Health and reduces Constipation: The right mixture of calcium and manganese reduces constipation. Calcium present in hard water combines with excess bile and fats and removes it through bowel movements.

Balances nerve and muscle function. Calcium, along with magnesium, maintains a delicate balance to support nerve and muscle function and lowers the risks of cardiovascular diseases.

Soft Water Pros

Maintains Appliances and Fabric. The minerals in hard water clog pipes, ruin appliances and wear out fabrics pretty fast. Hence, Soft water is a better option for plumbing, appliances, and fabrics. This is because soft water has a negligible or zero concentration of calcium and magnesium minerals. 

Does not disrupt detergents and soaps. Detergents and soap form healthy and bubbly lather with soft water. This is because soft water lacks the presence of minerals that react with sodium compound in soaps and detergents to form soap scum. It is therefore economical to use soft water in washing.

Soft Water is Friendlier To Skin and Hair. Soft water can effectively rinse away shampoo and soap from hairs and skin. It lacks minerals that stick to the skin and scalp, making it dull. For people with sensitive skin and skin issues, soft water is highly recommended.

Disadvantages of Hard and Soft Water

Hard Water Cons

Lather Formation: Hard water does not form lather with soap; instead, it forms a white precipitate of sodium or potassium stearate. The white precipitate is the scum. The scum inhibits the cleansing action of soap.

Stains: The formation of scum stains clothes and washes away their colours. 

Calcium deposits form a very hard layer on bath tiles, glass and bath fittings. The cloud-like watermarks on utensils are because of hard water.

Impact on hair and skin: Washing hair with hard water makes it dry and rough. Bathing with it makes skin dry and itchy. This is because the excess minerals present in the hard water form a curd-like substance and stick to hair and skin. So it’s no surprise that the use of hard water worsens conditions like dandruff, eczema, and psoriasis.

Reduces the Life of Appliances: Hard water wears down the appliances slowly, and the calcium deposits reduce the machines’ efficiency.

Corrosion of Pipes: Hard water deposits can corrode not only the pipe but also clog it. As a result, the water pressure reduces. Pipe corrosion can also result in the leaching of metals in the water, which is not safe for consumption.

Leads to other health problems. Though hard water acts as a calcium and magnesium dietary supplement, it poses potential health risks like neural diseases, diabetes, reproductive dysfunction, and renal dysfunction.

Soft Water Cons

Higher Levels of Sodium. This is a significant disadvantage of using soft water. Hard water softeners make use of sodium filters making soft water rich in sodium. Too much sodium is generally bad for health, and it alters the taste of water. However, not all water softeners make use of sodium; some make use of potassium, filters, or semi-permeable membranes. 

Lead Poisoning. Soft water, if transferred through lead pipes or kept in lead containers can easily lead to lead poisoning. This is possible because it can quickly dissolve lead.

Doesn’t strengthen bones. Soft water lacks calcium hence does not help in strengthening our bones and teeth.

Difference between Hard Water and Soft Water

 The difference between hard and soft water are explained below:

Summary

Hard water contains essential minerals and is sometimes the preferred drinking water. Not only because of its health benefits but also its flavour. On the other hand, soft water tastes salty due to the presence of sodium and is sometimes not suitable for drinking. Hence, it’s essential that we learn the difference and importance of both types of water. In this article, we learned the differences between hard and soft water. We also learnt their advantages as well as the disadvantage in detail.

FAQs on Hard and Soft Water

Q.1. What is the difference between hard water and soft water?
Ans: Hard water consists of calcium and magnesium salts, whereas soft water is devoid of minerals. Lather formation and cleaning take place more effectively with soft water, whereas hard water does not form lather with soap and forms stains on utensils, clothes, faucets, etc.

Q.2. What do you mean by hard and soft water?
Ans: Hard water contains calcium and magnesium salts, whereas soft water is devoid of minerals.

Q.3. How to check hard water and soft water?
Ans: The easiest and effective way to check for the hardness of water is through lather formation. If the water forms lather with soaps and detergents readily, then it is soft water, whereas if the lather is not formed easily, then the water ranks high in the hardness scale.

Q.4. How to identify hard water and soft water?
Ans: Soaps and detergents form a rich and bubbly lather with soft water, but they do not form any lather with hard water.

Q.5. What is the hardness and softness of water? Explain.
Ans: Water hardness is the amount of dissolved calcium and magnesium ions present in given sample of water. The removal of calcium and magnesium ions from hard water is known as the softening of water. Water softness can be achieved by using water softeners that use the ion-exchange method for hardness removal.

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