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What is Acidity (Low pH)?

As you learn about water quality and the possible issues, it is important to understand acidity and be aware of the possible treatment options for acid water.

Acidity is the ability of water or a solution to neutralize an alkali or balance a higher pH.

What is pH?

The pH scale measures how acidic or basic a substance is.

A pH value of 7 is considered “neutral.”

Solutions with a pH less than 7 are acidic.

Solutions with a pH value greater than 7 are basic or alkaline.

pH test strips

According to the Bronsted-Lowry theory of acids and bases, an acid is a substance that produces hydrogen ions (H+) in an aqueous solution, and a base is a substance that produces OH- ions in an aqueous solution.

pH measurement is reported in “logarithmic units” where each number represents a 10x change in the acidity/basicness of the water. This means that water with a pH of 6 is ten times more acidic than water with a neutral pH of 7.

While there are strong acids and weak acids, it does not take much change in acidity to reduce the pH of your water.

What Causes Acidity in Tap Water?

Water is considered “acidic” if the pH is measured at 6.5 or lower.

Tap water is acidic because it includes dissolved carbon dioxide (CO2) or other mineral compounds.

Carbon dioxide forms carbonic acid (H2CO3) in water, which dissociates into a hydrogen ion (H+) and a bicarbonate (HCO3-) ion. This causes the pH of the water to drop below 7.

Hard water (high levels of dissolved minerals) is often associated with more acidity in water.

Visit the United States Geological Survey (USGS) to learn more about regional variations in natural water pH.

How Does Acidity Affect Tap Water?

The normal pH range is 6.5 to 8.5 for surface water and 6 to 8.5 for groundwater.

Water with low pH is acidic and can cause the leaching of heavy metals, minerals, etc. into drinking water.

This acidity may also corrode piping, fixtures, and appliances that are not specifically designed to handle acidic water.

Acidity causes pipe corrosion

It will also corrode metallic parts such as copper, brass, and galvanized steel if the water contains enough contaminants like dissolved metals. This can also lead to pinhole leaks in copper plumbing.

If copper and manganese are leached into the water, it can cause green-blue stains on sinks and other fixtures or green corrosion on copper pipes.

People may notice a sour or metallic taste in the water at a lower pH.

How to Treat Low pH

There are several methods of treatment to reduce acidity in tap water and raise the pH.

A neutralizer is any acid-neutralizing substance that helps to raise the pH of water. It is also used in some soaps and detergents.

Common acidity neutralizers dissolve in a solution of water and include:

  • Sodium carbonate
  • Calcium carbonate (Calcite) in a calcite filter
  • Manganese oxide
  • Soda ash

Calcite filters utilize one or more of the substances above to raise the pH measurement and neutralize the acid.

A pH balancing system will inject soda ash into the water to raise pH and prevent corrosion from acidity.

Water softeners use ion-exchange resins to remove hardness from the water by exchanging sodium or potassium ions for calcium and magnesium ions. This leaves a residue of sodium chloride (NaCl) in your water, which makes it more alkaline (and less acidic).

Alkaline water is considered healthier by some people and generally more desirable than acidic water.

Test Your Water

Copper plumbing pipes

Testing your water for acidity or general pH level is very easy with simple test kits or strips you can order online or pick up at a local hardware store.

If you are unsure about your water, be sure to have it professionally tested, or at the very least, check the pH yourself to see if acidity is an issue.

If you have copper pipes, this is a good indicator that you should test!

If you are worried about the quality of your water, it is important to get educated. Understanding acidity and its potential treatment options can help you be more proactive in keeping your family healthy.