pH Of Reverse Osmosis Water: Is It Acidic?

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Wondering about the pH of reverse osmosis water? We’ve shared the information you’re looking for in this guide.

📌 Key Takeaways:

  • Reverse osmosis water has a pH of 5-7 on average.
  • Generally, drinking water that has been treated by the reverse osmosis process is mildly acidic.
  • You can increase the pH of reverse osmosis water by adding mineral drops to water or installing a remineralization filter as a final stage after the RO process.

⚗️ What pH is Reverse Osmosis Water?

The pH of a water source is its acidity or alkalinity, measured on the potential hydrogen (pH) scale. pH spans from 0 to 14 and is a measure of the number of hydrogen ions in the water, and their activity level.

The average pH of water treated by reverse osmosis is 5-7. That makes reverse osmosis water slightly acidic, or, at best, neutral.

Slightly acidic water is safe and healthy for humans to drink. Reverse osmosis won’t make your water extremely acidic or reduce its pH to unpleasant and potentially dangerous levels.

However, you may still want to decrease your reverse osmosis water’s acidity, and we’ve shared how to do this at the bottom of this guide.

Taking water ph reading with handheld ph meter

🆚 RO Water pH Compared To Other Beverages

How does the pH of reverse osmosis water compare to the pH of other common beverages?

RO water has a lower pH than bottled mineral water and normal tap water, but it’s usually more alkaline than coffee, soft drinks, fruit juice, and sports drinks.

You can compare the pH of reverse osmosis water and other common beverages in the table below.

LiquidAverage pH
Reverse Osmosis5-7
Tap Water6-8
Mineral Water7.4
Fruit Juice 2-4.5
Soft Drinks2.5
Sports Drinks2.9
Coffee4

🤔 Why Is The pH Of RO Water Important?

Wondering why you need to care about the pH of water from your RO system?

RO water’s pH levels are an indication of the water’s solubility. Water with a lower pH has higher solubility, meaning that more metals, chemicals, and other elements can easily dissolve in the water.

Some of these elements are essential for human health, but water with a reduced pH is also more likely to pick up dangerous impurities like lead.

📥 What is Acidity?

Acidic water is anything that has a pH of lower than 7.

Acidic water usually has quite a sour taste, and may take on a metal flavor depending on how low it is on the pH scale, and whether it has come into contact with metal pipes (acidic water is known for corroding metal).

ph scale

📤 What is Alkalinity?

Alkalinity is the opposite of acidity: alkaline or alkalized water is a pH higher than 7.

Usually, alkaline drinking water has a pH of around 8 or 9. Alkaline water with a high pH may have a bitter edge.

Alkaline water typically has a higher essential mineral content, making it better for our health all-round.

🧐 Is Reverse Osmosis Water Acidic?

In short, yes, reverse osmosis water is acidic. The pH of reverse osmosis water can drop all the way down to 5.

But, as we mentioned earlier, reverse osmosis water systems aren’t capable of making your water dangerously acidic, even after removing all the alkaline minerals.

📉 Why Does Reverse Osmosis Water Have A Low pH?

You may be wondering why reverse osmosis water doesn’t have a neutral pH level of 7, since it’s clean, pure water with no health-harming contaminants or impurities.

But there are several factors that contribute to the reduced pH of reverse osmosis water.

No Mineral Content

First off, when mineral ions such as calcium and magnesium are removed by an RO water treatment system, this causes a dip in pH, as these minerals naturally make water more alkaline. But this isn’t the main problem when it comes to the decrease in RO water’s pH level.

Reverse osmosis water has no minerals

“Hungry” For Impurities

The biggest issue occurs when RO water is exposed to air. Because RO water is pure water, it’s “hungry” for impurities. As a result, when water comes into contact with air, it pulls carbon dioxide out of the air.

The longer you leave a glass of pure RO drinking water out, the more acidic it’ll become. Expose your pure water to air for about an hour and it’ll end up with a pH level as low as 5.5. But it’s highly unlikely that your water will become any more acidic than this, no matter how long you leave it out.

📖 How to Test pH of RO Water

There are a couple of methods you can use to test the pH of RO drinking water:

Digital pH Meter

You can get the best pH readings of your RO water by using a digital water pH meter. These meters are widely available online.

To test your water with a pH meter:

  1. Place the digital pH meter in a container of RO water.
  2. Press and hold the calibration button.
  3. Wait for a stable reading to show on the screen.

You can also use a pH meter to test the pH of your unfiltered water to learn how much your water’s pH drops due to the RO process.

pH Test Strips

pH test strip sets are the cheapest and easiest way to find out where your reverse osmosis water falls on the pH scale. Soaking a pH strip in reverse osmosis water will provide you with an almost instant result, telling you how acidic or alkaline water is based on the color of the strip.

Be sure to buy strips that are designed to detect slightly acidic to slightly alkaline water. A testing strip set that measures all the way from 0 to 14 won’t be as accurate with its pH measurement.

pH strip sets are widely available and can be bought online for $5-$10 or so for a pack.

They’re useful to keep on hand, whether to initially assess water from a reverse osmosis filter system or to check the effectiveness of a re-mineralizing filter.

Testing water acidity with ph test strips

Lab Testing

If you’re looking for the most accurate measurement if your reverse osmosis water’s pH, you’ll benefit from a lab review.

There are hundreds of state-certified laboratories across the US that can assess a variety of water parameters, including pH.

Lab testing is a great option if you’re after a more accurate result than you’d get from pH testing sets. Lab reports can also determine your overall water quality, which may be important if you’re keen to examine the benefits of RO filtration in your home.

Litmus Paper

Litmus paper is a bit like the pH strip’s less capable younger brother. It works in pretty much the same manner to determine whether you have acid or alkaline water, but it’s less accurate.

To determine the pH of your RO with litmus paper, simply soak the paper in water from your reverse osmosis system. The paper will turn one of two colors to indicate whether you have acid or alkaline water. You won’t get the full spectrum of color shades as you do with a pH strip.

Note that tap water from an RO water system is usually only weakly acidic. This means that the litmus paper might not even detect acidity in your water, making it a fairly useless assessment method.

Litmus paper ph strips test

Red Cabbage Indicator Test

If you want to have a bit more fun in determining your RO water’s pH, try the red cabbage indicator test.

Yes, it’s exactly how it sounds: you use red cabbage to determine your water’s pH. Red cabbage contains a unique pigment that changes color depending on the pH level of the water it’s mixed with, a bit like a pH strip.

To perform the red cabbage test on your reverse osmosis water:

  1. Combine the cabbage with normal, non-RO tap water in a blender.
  2. After blending the cabbage, strain the solution to remove any large cabbage pieces.
  3. Add water from your RO water filtration system to the cabbage liquid and stir to combine.
  4. The water may take on a shade of red, and in that case, it’s a sign that it’s slightly acidic.

Though the cabbage testing method won’t provide you with a clear indication of your reverse osmosis water’s pH, it will at least give you an idea – and as an added bonus, it’s a fun novelty activity that you can do with your kids.

red cabbage ph test

🔎 How to Make Reverse Osmosis Water Alkaline

Wondering how to alkalize reverse osmosis water? Acidic drinking water isn’t pleasant, and luckily, there are a few simple ways to boost your RO water’s pH:

Install A Remineralization Filter

The best and easiest way to achieve healthy alkaline drinking reverse osmosis water is to purchase a remineralization (or mineral-adding) filter.

Remineralization water filters can be installed onto most under-sink or whole-house reverse osmosis systems after health-harming contaminants have been removed and act as final-stage filters.

These filters can improve water quality by introducing a rich dose of healthy minerals like calcium and magnesium. These minerals also improve water’s flavor, which can be affected by the RO water filtration process.

Use Mineral Drops

Want a budget-friendly way to re-mineralize your water? Buy mineral drops.

Mineral drops add a measured amount of minerals back into your water to support your health. These drops are cheaper, but they do require more effort than if you were to simply attach an extra filter to your RO system.

👨‍🔧 If you’re interested in the health benefits of re-mineralizing RO water, our guide on the different reverse osmosis remineralization options should prove useful to you.

❔ pH Of Reverse Osmosis Water: FAQ

What are the health effects of drinking acidic RO water?

Reverse osmosis water is only mildly acidic, so it has no health effects. However, if you have acid reflux, drinking water from an RO system might trigger your symptoms.

Does the reverse osmosis process alter water’s pH?

Yes, reverse osmosis alters pH. Normal unfiltered water has a neutral pH of around 6-8. After being treated by a reverse osmosis filter, water’s pH levels usually drop to 5-7 on the pH scale. This is because healthy alkaline minerals are removed during the RO process.

Is reverse osmosis water acidic or alkaline?

Reverse osmosis water has a pH of 5-7 on average, which means it’s slightly acidic or neutral. RO water is NOT alkaline because the reverse osmosis process removes pH-boosting minerals from water, making RO water acidic.

Is reverse osmosis water or distilled water more acidic?

Reverse osmosis water and distilled water are usually exactly the same on the acidity-alkalinity spectrum. Both water types are free from minerals that contribute to alkalinity, and both absorb carbon dioxide from the atmosphere due to their “hungry” status.

  • Jennifer Byrd
    Water Treatment Specialist

    Jennifer is a seasoned water treatment expert with over 18 years of experience in the industry, dedicated to improving water quality for clients across the USA and around the world. Her passion for helping others and extensive networking skills have led her to hold leadership positions in organizations like the North Port Area Chamber of Commerce and the Florida Home Builders Association. Jennifer is currently a managing partner at Redbird Water of West Texas, where she specializes in providing water filtration and solutions for residential, commercial, and industrial clients.

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