Everything You Need to Know About the pH of Water

Everything You Need to Know About the pH of Water

Everything You Need to Know About the pH of Water

Most of us have experienced something acidic in our lives, from the sulfuric acid you may have used in a high school chemistry lab to the burning of lemon juice in a papercut on the tip of your finger.

Did you know that where there is an acid, there is often a base on the opposite side of the coin that can cancel out that acidity? Have you heard of the pH scale? Don't worry if you haven't — it’s something that often gets overlooked unless you're working in a chemistry lab or maintaining a swimming pool. Let's look at what pH is and how it pertains to the water we drink. Why does the pH of water matter and will it change over time?

What Is pH?

First, if you're unfamiliar with the measurement, what is pH?

Scientists define pH as the measurement of how acid or base a substance is. It depends on the number of positively or negatively charged ions are in it. An acidic compound adds positively charged hydrogen ions, while a base adds negatively charged ones that are known as hydroxides.

pH is measured on a scale that ranges from zero to 14, with zero representing the acidic end of the spectrum, and 14 the basic end of the spectrum. A rating of seven, in the middle of the scale, is considered neutral. You probably have a lot of very acidic and basic substances in your home. 

Household bleach which you might use for cleaning or laundry is on the basic side of the scale with a pH rating of 12. The lemon juice you put in your morning tea, on the other hand, is on the acidic end of the scale with a pH rating of 2.

The pH scale counts hydrogen ions in a substance on a logarithmic measurement, meaning that as you move down toward the acid end of the scale, each number increases the number of hydrogen ions in the substance by a factor of 10. As you head toward the base end of the scale, the hydrogen ions drop by that same factor, replaced by negative hydroxide ions. 

Most of us aren't playing with incredibly acidic or basic substances, the ones that would fall on the extreme ends of the pH scale, but that doesn't mean that this measurement isn't important. 

Looking at the pH of Water

Pure water that doesn't have anything dissolved in it is considered a neutral substance, falling in the center of the pH scale with a rating of 7. Unless you buy bottled water, you're not likely to encounter a pure variety. Even many brands of bottled water dissolve minerals and electrolytes in their product to improve flavor. You may even see bottled waters marketed as 'alkali water' which means they have a higher pH, pushing them toward the basic end of the pH spectrum. 

On the extreme end of the spectrum, you get things like acid rain. Normal rain will have a pH value of between 5 and 5.5, but once it starts to combine with things like sulfur dioxide and other pollutants, it becomes more acidic, with its pH rating dropping to 4. That makes it about as acidic as tomato juice. 

Why Does pH Matter?

The EPA requires that drinking water be maintained at a pH range of 6.5 to 8.5 —not neutral, but close. That's because if the water you drink moves toward the acidic end of the pH scale, it can start to corrode the pipes and fixtures that it travels through, which can be dangerous. One example of this is the events that happened in Flint, Michigan. When the city switched its water source to the Flint River, it didn't add corrosion inhibitors to the water, which allowed it to leech dangerous levels of lead from the old pipes. 

Further research found that the city's water treatment plant left the river water's pH too low to prevent the lead carbonate in the pipes from dissolving. Ideally, the water traveling through those old lead pipes needed to be at a pH of 10 — Flint's water was between 7 and 8 on the pH scale. 

Incorrect pH in your drinking water can also be detrimental to your health. Your body maintains a pH level that's fairly close to neutral, usually between 6.5 and 7.5. If you're drinking water that's too acidic or too alkaline, or you're not eating right or you're stressed out, it can cause your body's pH levels to spike in one direction or the other, throwing everything out of balance.

Testing pH at Home

If you're curious about the pH of your drinking water, you'll be happy to know that it's easy to test for pH levels at home. You've got a few options here. You can head to your local pool supply and pick up a pH testing kit or some test strips. Swimming pools, especially those maintained with chlorine, must be kept at a specific pH level to ensure that they're safe for swimming. 

For educators or those looking for a more professional option, there are classroom-ready and custom kits that you can choose from, so you can turn your pH measurements into an entire lesson. 

In a pinch, you can even use the juice from red cabbage to create a pH indicator. Red cabbage water ends up at a pH rating of 7, making it neutral. It also contains a chemical that changes color when exposed to acidic or basic substances. It may not be as accurate as some of the professional kits, but it can provide you with some answers when you don't have anything else on hand.

Looking Forward

Every liquid in your household falls somewhere on the pH scale. In drinking water, it can play an enormous role in everything from the safety of the water coming from your tap to your overall health. Drink plenty of water, but make sure you're choosing the right water to ensure that your body stays balanced and maintains its own healthy pH level.

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  • Christina Nevaeh

    Alkaline water has a smoother and easier taste than other water. It's more pleasant.

  • Jessica Lunghi

    Thanks for the explanation

  • William Dickson

    I learned something new today

  • Emilio Iglesias

    Clear and concise

  • Molly Jones

    Exactly what I was looking for ;)

  • Jack Bond

    Excellent explanation, even I understood it.

  • Matthew Glenny

    Thanks for useful information

  • Alex Weatherby

    Our stomach produces very strong acids.

  • Sam Knight

    Very useful

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Megan Ray Nichols

Science Expert

Megan Ray Nichols is a science writer by day & an amateur astronomer by night (at least when the weather cooperates). Megan is the editor of Schooled By Science, a blog dedicated to making science understandable to those without a science degree. She also regularly contributes to Smart Data Collective, Real Clear Science, and Industry Today. Subscribe to Schooled By Science for the latest news.

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