Is Reverse Osmosis Water Acidic? How To Test Yours

Reverse osmosis systems are among the most popular residential water filters. But is reverse osmosis water acidic? Are the masses mistaken in trusting them? Keep reading for the answers to these and more questions.

Is Reverse Osmosis Water Acidic or Alkaline?

Put simply, yes, reverse osmosis water is acidic. While the pH level of tap water in Arizona ranges from 7.1 to 8.4, reverse osmosis water hovers around the 6.5 mark, representing greater acidity.

Is this going to have an impact on your health? Probably not. The Environmental Protection Agency states that water with a pH of 6.5 is perfectly safe to drink. 

This isn’t exclusive to reverse osmosis filters, by the way. Also popular are whole house filters in Phoenix, which will increase your water’s acidity as well. As you’ll see shortly, this all comes down to what these filters remove.

What is Acidity, Anyway?

Acidity is the opposite of alkalinity. Higher numbers on the pH scale represent greater alkalinity. The scale works logarithmically, with each number representing a 10-fold increase in alkalinity or acidity compared to the previous digit.

That would make reverse osmosis water with a pH of 6.5 10 times more acidic than unfiltered water with a pH of 7.5. Before you panic and start telling all your friends to rip out their reverse osmosis systems, though, it’s worth taking a look at the pH levels of other substances:

• Lemon Juice (pH: 2)
• Orange Juice (pH: 3)
• Tomato Juice (pH: 4)
• Black Coffee (pH: 5)

In other words, you consume liquids far more acidic than alkaline water on a daily basis.

Why is Reverse Osmosis Water Acidic?

Warning: This gets a bit nerdy.

According to Scientific American, acidic liquids easily transfer hydrogen ions into a solution. Weak acids (like reverse osmosis water) do this very easily.

Alkaline liquids work in the opposite manner. The more alkaline something is (i.e. the higher it is on the pH scale), the easier it will accept hydrogen ions.

So why is reverse osmosis water acidic?

Well, it’s all thanks to the filtration of alkaline mineral atoms. As we discussed in this post, reverse osmosis filters remove minerals like calcium and magnesium from your water.

Should you worry about the removal of these minerals? After all, calcium and magnesium are good for you, right?

While it is important that you ingest your required daily intake of those minerals, you’re not going to achieve that with water. Your body gets the bulk of its calcium and magnesium from your diet, which is why soft water is considered safe to drink, as we discussed in this guide.

Would Reverse Osmosis Water Impact an Alkaline Diet?

Given reverse osmosis water’s acidity, one might question whether it would counteract something like an alkaline diet.

The idea behind alkaline diets (as promoted by celebrities like Victoria Beckham) is that creating an “alkaline environment” in your blood can improve your overall health.

While the alkaline diet does have some benefits, according to Dr. Melinda Ratini writing for WebMD, this rationale is flawed. Nothing you eat or drink (not even reverse osmosis water) is going to have a major impact on your blood’s pH level. Your body regulates this level just fine on its own.

In other words, drinking reverse osmosis water isn’t going to “throw your blood off balance” or anything of that sort. 

This isn’t to say an alkaline diet is totally useless, though; your health will improve as a result of the foods you eat while on this diet. It just doesn’t happen in the way you’d expect it to.

In fact, the chemicals you would ingest if you didn’t have a reverse osmosis filter (or some other type of system) would impact your health much more severely than any minor acidity would. This is why reverse osmosis systems in Phoenix are so popular. Compounds like lead, arsenic, and chlorine (all of which are prevalent in America’s drinking water, as we discussed here) will harm you over the long haul. Acidity is just a byproduct of removing these minerals from your drinking water.

How to Test Your Water’s Acidity

While you should know by now that reverse osmosis water’s acidity shouldn’t be a major concern, you might still want to see exactly where yours falls on the spectrum. You can also check out our article about the ideal water pH level for your home as a reference.

There are three reliable methods for doing this. Let’s take a look at them.

pH Strips

When you soak a pH test strip in any given liquid (your reverse osmosis water, in this case), it will change color based on where it falls on the acidity-alkalinity spectrum.

Your best bet would be to buy a strip designed to test within the 5.5-8.5 range, in which your reverse osmosis water will likely fall. If you get a strip that tests too broadly, you may find it hard to distinguish between the hues that would give you an accurate idea of your water’s measurement.

Litmus Paper

Litmus paper works similarly to a pH strip, only with less accuracy. When you soak litmus paper, it will simply turn one of two colors based on whether it’s acidic or alkaline. Keep in mind that reverse osmosis water is a relatively weak acid. Depending on what type of litmus paper you choose, your water may not even show up as acidic.

Local Testing Facility

What a lot of people don’t realize is that many American cities have local water testing services run out of universities or local government facilities. As we discussed in our article on hard water testing, you can send your water into these facilities and have it analyzed.

The results you’ll get from these sources will be much more accurate than the approximations you’d find with pH strips and litmus paper.

Bonus Method: Red Cabbage

You can also perform an approximate test of your water’s pH level using — believe it or not — a piece of red cabbage. Red cabbage contains a pigment that will change color based on the pH level of whatever you mix it with.

To perform this test, you’ll need to blend the cabbage with any water (not necessarily the water you’re looking to analyze). Strain the resulting liquid to remove chunks of cabbage.

Then, pour your reverse osmosis water into the strained liquid. Stir it thoroughly. If the mixture turns red, that’s a sign that your water is acidic.

Again, remember that reverse osmosis water is a weak acid. It’s not going to turn the liquid bright red like vinegar or lemon juice would but you may notice some change.

Does Reverse Osmosis Make Water Acidic? Conclusion

By filtering alkaline minerals, the reverse osmosis process will leave your water slightly acidic. This is normal; you’ll find it happens with all types of filtration.

The increase in acidity is very slight and will not have an impact on your health. Your body controls its internal pH level quite well regardless of what you consume.

If you want to find out exactly how acidic your drinking water is, use one of the above methods. Your local water testing facility will yield the most accurate results.

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