Difference between Hard and Soft Water

Updated on March 8, 2017

The water we drink, wash our clothes in or cook our food with is not necessarily all the same thing. It is classified as either hard water or soft water. It only takes a few minutes to learn the difference between the two.


Calcium deposits on a faucet caused by hard water

Hard water is a type of water containing substantial amounts of dissolved minerals such as calcium and magnesium. It starts as rainwater that seeps through the ground. As it is absorbed into the ground and goes into the waterways, it is naturally purified and imbued with minerals such as sodium, magnesium, chalk and lime. This process of natural filtration reduces the possibility of lead and copper occurring in the water. This makes hard water ideal to drink because of its mineral content and the health benefits it offers. In addition, hard water has a unique flavor to it, making it a preferred drinking water. In the US, most water is hard water as it comes from beneath the ground.

Hard water can cause corrosion in pipes as it leaves deposits called scales. Hard water also causes dishes to develop spots and showers to accumulate soap scum. When these happen, vinegar and other cleaning solutions should do the trick in removing the deposits. Hard water is also bring known to bring down the performance of washing machines and water heaters.

Soft water
Soft water promotes the lathering action of soap

Soft water is surface water characterized by low concentrations of calcium and magnesium ions. It is rainwater collected from lakes, rivers and the drainage basins of rivers made of impervious rocks low in calcium. It also refers to water that has gone through a water softening process, although the technical term is “softened water”. In the US, water that has less than 60 mg/L of calcium carbonate content is classified as soft water.

Soft water contains few calcium ions, therefore, it does not leave calcium deposits in pipes and water heating systems. It does not reduce the lathering effect of soaps, and it does not leave soap scum in normal washing. Soft water does not contain minerals that can cause dry skin. It is also better for washing clothes and dishes as it works well for rinsing. Dishwashers and washing machines are also known to work better with soft water. A certain type of salt is used when softening water, which causes a not-so pleasant taste.

Hard vs Soft Water

So what’s the difference between hard and soft water? Hard water is rain water that has seeped deep into the ground and becomes part of a spring or a water well. Soft water, on the other hand, is surface water collected from lakes and rivers, including water in river basins that has not seeped into the ground. The term is also used to refer to water that has gone through a water softening process.

Unlike hard water, soft water has a low calcium and magnesium content. This means that soft water will not leave calcium deposits in pipes like hard water does. In addition, these minerals make hard water a healthier drink compared to soft water. These minerals also lend hard water a pleasant taste compared to a somewhat salty or bitter aftertaste common in soft water.

Comparison Chart

Hard WaterSoft Water
Rainwater that has seeped underground and collected in water wells and springsSurface water collected from lakes and rivers
High in calcium and magnesiumLow mineral content
Water with 121-180 mg/L calcium carbonate content (US standards)Water with less than 60 mg/L of calcium carbonate


Watch this YouTube video for more about hard and soft water