pH of RO Water: Is it Acidic?

Reverse osmosis is one of the most effective and convenient water purification technology that removes 99% of the contaminants. Your drinking water then is clean and pure. This is accomplished by using the osmosis principle to purify water. Just that it works in reverse. Basically the water is pushed through a membrane so fine that all the impurities and minerals are left behind.

After the process, RO water becomes slightly acidic with a pH between 5 and 6.5. This is a natural feature. Drinking RO purified water is absolutely fine.

There are few things to keep in mind when talking about acidic and alkaline water so let’s make these points clear in the rest of the article.

See Comparison: Reverse Osmosis Vs Alkaline Water

Is acidic water dangerous?

Acidic water is a broad term that can be used in different contexts. This means a few different things but to keep it simple – acidic water is not dangerous in itself, but in specific conditions, it can be.

If this is a bit confusing stay with me and everything will become clear. There are certain ways when acidic water can become dangerous in the long term. The biggest of them is that acidic water can corrode the piping system of your house, releasing chemicals you don’t want like traces of copper or even lead. There are known ways to test your water pH and if you suspect that water coming into your household system is acidic you should test in one of few ways. These are described later in the article.

And that’s where the potential danger of acidic water, pretty much ends. What about drinking acidic water?

Related Article: Reverse Osmosis vs Distilled Water

Related Article: Does Reverse Osmosis Remove Lead?

First of all, let’s make it clear what acidic means

Acidity and alkalinity are measured on a pH scale. Basically it’s a matter of atoms being in one place or another. For us, it matters only a little if the water we drink is alkaline or acidic, really.

Your stomach has a pH value of 2 and it works to keep it this way. Meaning everything that you consume, no matter how acidic or alkaline it is will be changed to the pH value of 2, in the stomach, before it can be digested. Your body is fantastic at adapting and self-regulation. It keeps an almost neutral internal pH of 7.4 at all times. In fact, even when you put drinks in your mouth, contact with saliva already starts to alter the pH of food and drinks.

It’s only natural that different liquids that we drink have different pH levels.

Mineral Water7.4 pHBeer4.5 pH
Tap Water6-8 pHCoffee4 pH
RO Water5-6 pHTomato Juice4 pH
Soda2.5 pHOrange Juice3 pH

Yes, a lower than normal body pH balance, during the long term is a symptom that something is not right. But there are other matters like lifestyle choices, amount of stress, and such that affect it so much stronger.

According to the United States Environmental Protection Agency, water with a pH between 6.5-8.5 is safe to drink. This might create doubts because RO produces water that might be below 6.5. But as we’ve seen, many liquids that we consume are even more below the norm. Plus there are ways to remineralize and change the RO water pH if you desire so.

To put it simply. Unless you have a known health condition, acidic water, or any other beverage that your drink is nothing to worry about.

Should I do something about RO water?

If you already own a RO system and the water that is coming from it is acidic and you don’t like it, there are 2 things you can do:

• Remineralize it manually – here’s a guide I have on how to add minerals to your water

• Upgrade the system with a remineralization unit

Test you water

So if you’re running an RO system, without a remineralization unit, then you’re probably getting slightly acidic water. As we know now that’s nothing to worry about.

But if you don’t have any water purification system and you want to be certain about the water that is coming from your tap there are ways to test it.

  • Litmus Paper

It’s a special paper strip with a simple measure of testing if the liquid substance, in this case, plane water is acidic or alkaline. Litmus papers change color based on whether water is acidic or alkaline. It does not show how acidic or alkaline the water is just that it is on one side of the scale.

It could be interesting to use them to test the pH of your mouth. You can see how consumption of drinks like soda or juices affect the pH balance of saliva and better understand or show kids why it’s important to brush teeth.

  • pH strips

They work in the same way that Litmus papers do. The one key difference is that it’s possible to get strips designed to test water acidity or alkalinity within certain ranges. For example, a pH strip can work between 5.5-8.5 range showing a more precise result.

  • A digital pH meter

This will be the most precise way to test water pH at home. People see colors differently, so there will be some guesswork with pH strips or Litmus papers.

Strip tests are easy and convenient for quick tests, but they can go out of date or become damaged by improper storage. A digital pH meter will be reliable in the same way that a thermometer is.

  • Local water testing laboratory

A populated area with public services usually has a water testing facility that is responsible for overseeing water quality in the area. It can be run by local authorities or universities. If you look for one you might get in touch in sending them your water sample for a more detailed analysis. The results you’ll get this way will be the most accurate than any test you can make at home.

Differences between acidic RO water and Alkaline water

This might sound odd, but there is no difference in RO or alkaline water once you swallow it. Your stomach just deals with that as with any other water, the pH is out of the question here. Also, there is no clear evidence that alkaline water is better than plain water with a neutral pH.

The only difference between these types of waters that matter is what you are doing with them beforehand.

Water with normal (7) or higher pH will, in general, taste better on its own. Also, hot drinks like coffee brewed with normal pH water will taste better because of the molecular structure of alkaline water.

Water is important for you and your health in general. So try to get the amount that you need whenever it’s RO or Alkaline water.

But the next step in water quality is some way sort of water purification system. We know that the RO system works wonders to produce crystal clear water that is pure and good to drink. That’s doubly true for a household that receives questionable quality water that can be contaminated along the way.

In my experience, RO systems, like for example countertop reverse osmosis filters, can cover all the needs of purifying and remineralizing water making it neutral pH and tasting so good.

I hope that helps and clears some of what is really confusing in the field of water purification.


This is my blog about the ways and solutions that can help you improve your health by taking more value from drinking water. As improving health means a lot to me, I decided to create the Water On Top project with the purpose to reveal the benefits of water, the finest products to take our daily water to another level, and much more great stuff about water that I believe is on top of our nutrition.

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