Hard Water and Soft Water

You must have heard about the hard water problem of Gautam Budh Nagar (Noida) – a satellite township located in Uttar Pradesh state of India. The deposition of salts of magnesium and calcium around the shower head, taps etc. is common in Noida. In a recent survey it is found that the level of dissolved solids (TDS) in the city is 2000 mg per litre against the permissible level of 500. Calcium and magnesium minerals are found in abundance in the soil of Noida which causes high amounts of minerals in the water there. Like Noida many cities of the world are facing the same problem of hardness of water. In this article we will discuss the difference between hard water and soft water in detail. But before understanding the difference between them you need to understand what is hard water and soft water? So, let us understand hard and soft water definitions 1st.  

What is Hard Water? 

Hard water is the water that contains higher concentrations of minerals such as calcium and magnesium. Presence of sulfates, carbonates, bicarbonates of calcium and magnesium makes water hard. Apart from calcium and magnesium, a variety of dissolved polyvalent metallic ions such as iron, aluminium, zinc and strontium also contribute. 

According to WHO, water containing calcium carbonate at concentrations 60-120mg/l is moderately hard, 120-180mg/l is hard, and more than 180mg/l is very hard. Water hardness is the measure of the capacity of water to react with soap and form lather. Hard water generally forms insoluble curd with soap instead of lather. 

Hard water is harmful for machines, boilers, human health and marine animals as well. It causes corrosion and scaling. 

Types of Hard Water – Hard water can be divided into two types –

  • Temporary hard water

  • Permanent hard water 

Temporary hard water contains bicarbonates and carbonates of calcium and magnesium. It is also called alkaline hardness. It can be removed by boiling the hard water. Thus, removal of temporary hardness of water is cheap or less expensive. Reaction involved in removal of temporary hardness of water by boiling can be expressed as follows –

Ca2+ + 2HCO3- Heat → CaCO3(S) + H2O + CO2

Hardness                  Scale 

On heating the temporary hard water calcium carbonate or magnesium carbonates get precipitated. 

Permanent hardness of water is due to chlorides and sulfates of calcium and magnesium. It is also called non-alkaline hardness. This type of hardness can be removed by treating water with soda. Methods used in removal of permanent hardness of water are expensive. 

What is Soft Water?

The water which gives lather with soap water is called soft water. It contains lower concentrations of minerals such as calcium and magnesium. It contains sodium ions. According to WHO, water containing calcium carbonate at concentrations below 60mg/l is soft water. 

Typical dietary contribution of calcium and magnesium is over 80% of the total daily intake. Out of this 30% Ca and 35% Mg will be absorbed. 5-20% of Ca and Mg comes from drinking water. 

Difference Between Hard Water and Soft Water 

We have explained above what hard and soft water is, now you can easily differentiate them. Difference between hard and soft water is given below for your better understanding –

S.No.

Hard Water 

Soft Water 

1.

It has higher mineral concentration than soft water. 

It has lower mineral concentration than hard water.

2.

It contains calcium carbonate at concentrations more than 60mg/l. 

It contains calcium carbonate at concentrations below 60mg/l. 

3.

It mainly contains calcium and magnesium ions. 

It contains calcium, magnesium and sodium ions as well. 

4.

It gives an insoluble curd with soap rather than lather. 

It gives lather with soap.

5.

It cannot be used as drinking water daily. 

It can be used as drinking water daily.

6.

It has a characteristic taste. 

It has a salty taste. 

7.

It is formed when water flows through limestone and chalk and other rocks. 

Rainwater is generally soft water. Apart from this soft water can be produced by passing hard water over an ion exchange resin. 

8.

It is not suitable for boilers and other machines.

It can be used in boilers and other machines. 

9.

It causes adverse effects on skin and hair.

It doesn’t cause any adverse effects on skin and hair. 

10.

It causes deposits of hard calcium or magnesium salts on taps, shower heads etc.  

It doesn’t cause deposits of hard calcium or magnesium salts on taps, shower heads etc.  


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