Is Hard Water Acidic?

Is Hard Water Acidic?

Water is classified as hard or soft based on its constituents and the concentration of minerals like magnesium and calcium that are dissolved in it. Although, determining whether hard water is acidic or alkaline is a different story altogether. Hard and soft water resources have varying levels of pH, and here’s what you must know about them.

Hard water is generally more alkaline and soft water is more acidic. Due to its high concentration of dissolved minerals, hard water results in a pH value of greater than 7 – which indicates its alkalinity, while soft water results in a pH value of less than 7 – making it acidic.

Pure distilled water has a pH value of 7 which indicates that it is neutral and pure. A difference in pH values of hard and soft water also leads to various characteristics and uses. Hard water based on its alkalinity has a few key characteristics that are absent in soft water. To find out more about what is best for you, keep on reading!

Why is Hard Water Not Acidic?

Being a universal solvent, water contains a high concentration of dissolved minerals such as Magnesium, calcium, and sodium. These minerals are dissolved in the water as it seeps through underground soil beds and rocks and eventually collect in large aquifers.

Water hardness is normally expressed as the number of parts per million (ppm) of calcium carbonate present in the water. Here’s a table compiling the ppm value of different water:

Type of Water Hardness
Soft water 10–50 ppm
Slightly hard water 50–100 ppm
Hard water 100–200 ppm
Very hard water Over 200 ppm


Alkaline compounds dissolved in water lead to an increase in the pH value of water. These alkaline compounds such as metals and salts dissolve in water to form a basic solution.

Hard water contains a high concentration of calcium ions that when dissolved in water form calcium hydroxide, most commonly known as limewater. Limewater is alkaline and it leads to an increase in the pH value.

Similarly, magnesium salts formed as a result of magnesium ions dissolved in water are also alkaline. These dissolved compounds distinguish the pH values of hard and soft water.

The Relationship Between pH and Hardness of Water

While the difference in the pH between alkaline and acidic elements is well known, here are the effects of these pH values on the hardness or softness of water.

Hard water has a high concentration of mineral compounds that give water its characteristic alkaline properties.

Alkaline compounds include salts, metals, and minerals that turn water more basic when they are dissolved in it. Due to the excessive concentrations of these hard metals dissolved in water, hard water displays a pH level that is higher than 7. Therefore, the pH value and the hardness of water are directly proportional.

The higher the pH value, the harder the water is!

Is Acidic Water Hard or Soft?

Acidic water has a lower concentration of dissolved minerals however, it has a much higher concentration of sodium which is acidic. Higher concentrations of dissolved sodium lead to a pH value that is below 7.

This makes acidic water soft and gives it its characteristic properties of a slightly metallic taste with comparatively higher sodium content. With a pH value of 5.5 or 6, acidic water qualifies as a suitable drinking water resource. Therefore, the lower the pH value, the softer and more acidic the water is!

What Should Be the pH of Drinking Water?

According to the U.S Environmental Protection Agency recommended pH of drinking water must range between 5.5 to 9.

Water resources with a pH closer to 9 will be determined as hard water resources which are inherently alkaline whereas sources with a pH closer to 5.5 will be considered soft water resources which are more acidic.

Can The pH Levels Be Treated?

If the water resource available is not suitable for use due to its pH value, it can be treated. If the water is too soft for use and is causing problems in the household, an acid neutralizer may be used to reduce acidity and increase its pH value.

The neutralizer may prevent corrosion due to the high acidic content in the plumbing lines. Soft water is more suitable for household chores of washing than hard water.

On the other hand, if the water is too hard then it can be softened using a water-softening system.

Through this, the pH value of water is decreased and it is made more acidic. The system removes some dissolved minerals from the water and filters it out to make it softer for use.


Will Hard Alkaline Water Be a Problem in Everyday Household Use?

While hard water with its high concentrations of minerals is great for a regular mineral intake for your body, it might not be very suitable for other household chores.

Washing utensils might leave hints of limestone scaling on them while plumbing pipes might develop clogs due to mineral deposits and lead to lower water pressure in the water lines.

Will Soft Acidic Water Be a Problem in Everyday Household Use?

Soft water with its higher acidic properties and sodium content might not be suitable for people who suffer from high blood pressure.

In terms of household chores, the acidity of the water might lead to faster corrosion of water fixtures and appliances. This can easily be fixed with an acid neutralizer added to the water storage tank.

Will Water Become Acidic with Reverse Osmosis?

The process of Reverse Osmosis removes dissolved solids and small particles from the water to make it healthier for consumption, therefore, it also removes some of the minerals.

This leads to the water being more acidic than alkaline as it exits the process for consumption and use.

Final Thoughts

Hard water is more alkaline and not acidic. However, if you want a different pH level for your water, some processes may help you reach the pH levels of your choice. Therefore, through observations, you may first determine the required pH value that would be suitable for you and your family and then make decisions accordingly.

The Filter Guy

Scott Birch is a water filtration installer and designer. He has worked in the industry for many years and is very familiar with and knowledgeable about residential water treatment equipment. Scott enjoys helping people get the most out of their water filtration systems and ensuring that their homes are getting the best possible quality of water.

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