How to Check the pH Level of RO Water

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Checking the pH of your reverse osmosis water is not only interesting, but it can indicate your system’s functionality and alert you to any potential problems.

For example, If your RO water has a pH level that is too high, it may indicate things are not being filtered out properly.

So, how can we best check the pH of your RO water? Read on!

Key Takeaways

  • You can test the specific pH of your RO water using a pH meter or pH test strips.
  • You can test whether your RO water is an acid or base using Litmus paper or red cabbage.
  • The most reliable and accurate pH measure is from a digital pH meter.

How to Check the pH Level of RO Water

You can use several methods to test the pH of your RO water, some being considerably more effective than others. The most popular are as follows.

pH Meter

A digital pH meter is the most accurate for reverse osmosis water pH readings.

  1. Calibrate your pH meter as per manufacturer guidelines. This might involve testing it in a substance with a known pH and adjusting the meter accordingly.
  2. Clean the probe with deionized water and dry it using a tissue.
  3. Collect a water sample in a clean container deep enough to cover the probe tip. Let it sit to stabilize the temperature.
  4. Put the probe in the water sample and wait for the meter to stabilize.
  5. Record the pH reading from the meter, which ranges from 0 to 14. Pure water should read around 7.
  6. A reading under 7 means the water is acidic, while over 7 indicates it’s basic.

digital pH meter

pH Test Strips

pH strips are easy to use and can be purchased online or from a drugstore.

  1. Fill a clean, clear glass with RO water.
  2. Dip one end of the strip into the water and remove it, shaking off excess water.
  3. Wait for the strip to change color.
  4. Compare the color with the chart provided with the strips.
  5. Identify your RO water’s pH based on the color match.

Litmus Paper

While litmus paper can give you a quick and easy indication of whether your reverse osmosis water is acidic or basic, for more accurate readings of pH levels, use pH strips or a pH meter.

  1. Gather a sample of the RO water you want to test in a clean container. Make sure the water is deep enough to fully submerge the litmus strip.
  2. Dip the litmus paper into the water sample for a few seconds. Ensure the paper is fully submerged, but do not stir or move it around, as it may affect the results.
  3. After removing the litmus paper from the water sample, observe any color changes. The strip will change color based on the acidity or basicity of the solution.
  4. Use the color change to determine if your sample is acidic or basic. Remember, litmus paper doesn’t provide a specific pH value but simply indicates whether a substance is an acid or a base.

Red Cabbage

While not super accurate, the red cabbage test is a fun thing to try at home. The color of the pigment in red cabbage changes depending on the pH level of the solution it is mixed with.

  1. Blend the cabbage with regular tap water, then strain the mixture to separate the cabbage chunks, leaving behind a purple liquid.
  2. Add the reverse osmosis water to the cabbage liquid and give it a good stir. If the color turns red, that means it is acidic.

So What Is the pH of Reverse Osmosis Water?

Reverse osmosis water usually has a pH ranging from 5 to 7, with a typical value of 6.5 before exposure to air and 5 to 5.5 after exposure. These levels fall within the safe drinking range and only concern individuals susceptible to gastric reflux who must steer clear of acidic beverages.

pH scale

Why Is Reverse Osmosis Water Acidic?

During reverse osmosis, water undergoes a purification process where alkaline minerals are stripped away. This action theoretically balances the water to a ‘neutral’ pH of 7.

However, when water is pure and carries a neutral pH, it loses its buffering capacity, which is its ability to resist changes in pH. Essentially, it becomes a sponge for any substance it can dissolve. In the case of reverse osmosis water, its first encounter is usually with air, allowing it to absorb carbon dioxide and form carbonic acid, which is mildly acidic.

Despite this, there’s a silver lining. The water remains primed to absorb other substances, which may increase the pH levels. This means it can be easily remineralized using a remineralization filter or mineral blends.

If you have any questions about testing the pH of RO water please don’t hesitate to leave a comment below!

About the Author Alexandra Uta

Alex is a content writer with an affinity for research and a methodical attention to detail. Since 2020, she has fully immersed herself into the home water treatment industry only to become an expert herself. Alex has been using water filters and similar products for years which has gained her lots of hands-on experience.
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