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Hard water and Soft water: Definition, Types and Differences


Most often, water is filled with chemicals and minerals. Based on the different types of minerals in the water, water can be classified into hard water and soft water. According to definition, Hard Water is water containing large amounts of minerals such as calcium and magnesium. On the other hand, soft water is the type of water that contains lower amounts or lower concentrations of minerals like calcium and magnesium. Thus, we can conclude that minerals in water determine the hardness or softness of water.

It has to be noted that determining the hardness of water or softness of water requires extensive testing. One cannot simply determine or classify hard and soft water by simply measuring the mineral content of the sample.

Hard Water

According to WHO, water containing calcium carbonate at concentrations 60-120 mg/l is moderately hard, 120-180 mg/l is hard, and more than 180mg/l is very hard. The presence of minerals in the water can also affect its hardness. For instance, apart from minerals such as calcium, magnesium presences of sulfates, carbonates, bicarbonates of calcium and magnesium, a variety of dissolved polyvalent metallic ions such as iron, aluminum, zinc, and strontium can contribute towards the hardness of the water.

Depending on the types of minerals present, hard water is divided into the following types:-

1. Temporary Hard Water
The water that contains bicarbonates and carbonates of calcium and magnesium is known as temporary hard water. The hardness caused due to their presence is also known as alkaline hardness. However, this hardness can be easily removed by boiling. Due to the heat from boiling, the bicarbonates and carbonates are converted into calcium carbonate compounds.

2. Permanent Hard Water
Permanent Hard Water is known to contain chlorides and sulfates of calcium and magnesium. The hardness caused due to their presence is also known as non-alkaline hardness. However, methods for removal of permanent hardness are expensive as non-alkaline hardness is difficult to remove.

Even though the minerals present in hard water are beneficial to our health, hard water has harmful effects. Hard water is known to cause corrosion and scaling and have adverse effects on machines, boilers, human health, and marine animals.

Soft Water

Soft water is defined as the type of water containing lower amounts of minerals such as calcium and magnesium. As we know, the hardness of water is also known to measure the water's capacity to react with soap and form lather. Therefore, we can define soft water as the water that forms foam or lather. According to WHO, water containing calcium carbonate at concentrations below 60 mg/l is soft water.

As soft water is not rich in minerals, it mainly contains sodium ions. Thus, if you are experiencing blood pressure problems, then ingesting soft water may cause side effects due to the high sodium levels. Another disadvantage of soft water is that it may contain higher traces of lead. If the pipes are not appropriately maintained or treated for leaching of lead, then the soft water passed through these pipes is more likely to pick up lead from the inside. This may result in negative health anomalies.

Difference between Hard Water and Soft Water

The difference between hard water and soft water is tabulated as follows:

Hard Water Soft Wate
If the water consists of higher concentrations of minerals, then it is classified as hard water. If the water consists of lower concentrations of minerals such as magnesium, calcium then it is classified as soft water.
Hard water does not form lather or foam. Soft water forms lather and foam.
Hard water leaves spots on the washed dishes after they are dried Soft water does not leave any spots on dishes after they are dried
Soap is not effective against hard water. FSoap is effective against soft water.
Hard water may cause side effects on the skin, hair. Hair and skin may become dry due to hard water. ASoft water does not cause any side effects on the skin, hair. Instead, hair and skin may become soft.
Hard water forms when water flows through limestone and chalk and other rocks. Soft water is formed by passing hard water over an ion exchange resin.
Hard water has a characteristic taste and isn’t suitable for heavy machinery, boilers, and other appliances. Soft water is known to have a salty taste and is widely suitable for machinery, boilers, etc.
Hard water is rich in minerals. Hence it mainly contains minerals such as magnesium and calcium. Soft water is not rich in minerals. It mainly contains sodium ions.
Hard water is preferred as drinking water Soft water is not preferred as drinking water.
Example: Water found in wells, groundwater Example: rainwater


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