Why Is My Reverse Osmosis Water pH High?

Why Is My Reverse Osmosis Water pH High?

The water from Reverse Osmosis (RO) is in its purest H20 form when it has a balanced pH of 6 – 7. The filters in the RO system, including the semi-permeable membrane, remove most of the alkaline matter, giving your RO water an ideal pH level which makes it safe and healthy for consumption. However, on rare occasions, your RO water can show high pH levels when tested.

The pH levels, in RO water, rise when it loses carbon dioxide. This usually happens when the RO water is left to sit for some time and gas escapes causing it to become more alkaline.

When dealing with high levels of pH in RO water, common questions include:  What are the health implications of drinking alkaline water?  How do I prevent this from happening? How to balance pH levels in RO water? In this article, we are going to find some answers.

Read my comprehensive article about reverse osmosis.

What Makes the pH Level Rise in RO Water?

A reverse osmosis system is specifically built to maintain balanced pH levels. If high levels of pH are noticed, it is an abnormality.

What may have happened, in such cases, is that CO2 in the water is displaced by oxygen and nitrogen from the air, leading to degasification.

With low levels of CO2, there’s a shift in the equilibrium of the water, leading to increased pH levels.

The pH imbalance in the water also occurs due to high amounts of chemicals, pollutants, sediments, and contaminants in the water.

The only time it can happen to RO water is when the filters are malfunctioning or when the RO water has been sitting out in the air for far too long and the CO2 has evaporated.

Is It Harmful to Consume Reverse Osmosis Water with High Ph Levels?

Water with high pH levels can be good or bad, depending on what’s raising the pH levels. There are times when the water is alkaline when it has a balanced range of minerals and therefore is filled with electrolytes. This is a good thing.

If your RO water has all the good minerals, it is safe to drink. According to UCLA health, there is no evidence of harm found in water with a pH of between 7 and 8.

On the contrary, chemical and heavy metals in the water also raise the pH levels. In that case, the water is unsafe to drink, which is a clear indication that the RO system is not working and needs a repair or filter replacement.

When the pH levels go lower than 5.5, water becomes acidic and that can be extremely harmful to drink. To combat this, the RO system is often customized with an alkaline filter.

High levels of pH make the water more alkaline and while that isn’t necessarily harmful to health, it does change the taste of the water, making it bitter.

High levels of pH also lead to a buildup of calcium and magnesium in the water pipes and can make our skin dry and itchy.

How to Reduce High Levels of pH in RO Water?

If your RO system is working perfectly and none of the filters are malfunctioning, then there might be other factors raising the pH levels of your water. To reduce insanely high levels of pH in the water, most people opt for acid injections.

The acid injection is a system fitted at the point of entry and consists of a chemical feed pump. This system itself is resistant to corrosion and it works by injecting an acetic solution into the water with high levels of pH.

The acetic solution is mainly white vinegar, but citric acid or alum can also be used for the same purpose.

Although hydrochloric acid or sulfuric acid also does the job, even their weak solution can be hazardous. It is only recommended to use these two solutions when the untreated water is a pH of 11 or more.

When alkaline water is introduced to acid, the pH levels balance out, and the water becomes neutral with a pH of 7. The taste of the water also improves and the water no longer corrodes metals such as brass, copper, iron, zinc, and aluminum.

The Pros and Cons of High Levels of PH in Water – At a Glance

If your RO water has tested clean and safe for drinking but still has a high level of pH, it is most likely due to minerals present in the water.

As such, the water is simply alkaline and in most cases is considered safe for drinking purposes. However, If you are still unsure, the table below highlights the pros and cons of drinking alkaline water.

Pros of Alkaline Water Cons of Alkaline Water
The minerals in alkaline water have anti-aging effects Drinking alkaline water in high amounts can lead to nausea and imbalance in the body’s pH levels
Alkaline water contains electrolytes and helps maintain body hydration Alkaline water can lead to high levels of alkaline in the blood, leading to stress on the organs
Alkaline water inhibits pepsin, the enzyme that causes acid reflux Alkaline water can inhibit the stomach enzymes that help with digestion


Frequently Asked Questions

Q) What is the pH of reverse osmosis water?

RO water is slightly more acidic than pure water and has an ideal pH level of 6 – 7. If the pH levels are lower than that, an alkaline filter can be added to the system to increase the pH value.

Q) Is it important to remineralize reverse osmosis water?

Alkaline water includes electrolytes due to balanced minerals within it. When the RO system eliminates all the minerals, you can add them back in using a re-mineralizing filter.

Q) What are the natural materials that raise the pH of water?

A high concentration of calcium carbonate (limestone) and synthetic magnesium oxide (seawater/groundwater sediments) present in the water increases its pH level.

Final Thoughts

All in all, a high level of pH in reverse osmosis water is a rarity and a sign of a faulty system or a malfunctioning filter. If you notice a bitter taste in the water or experience dry and flaky skin, get the water tested immediately. If your RO water is alkaline, chances are, it is not filtering out harmful chemicals and heavy metals.

Boch Richard

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children.

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