Reverse Osmosis Vs Distilled Water – What’s the Difference?

With so many water purification techniques available these days, it is easy to find yourself wondering which one suits best for you. Distillation systems have been around for generations, but reverse osmosis claims to be the new technology in the world of water purification.

So, what is the difference? Is one better?

To help you out in choosing between the two, here we have an in-depth explanation of what these processes are and what impurities they target, along with all the pros and cons of each.

Let’s get right to it!

Reverse Osmosis

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Reverse osmosis is a water purification process that removes impurities with the help of semi-permeable membranes. This is based on a natural process called osmosis in plants. Osmosis allows a natural movement of water from a higher concentration to a lower concentration.

Reverse osmosis takes advantage of this natural phenomenon. High pressure is used to push water in the opposite direction. Here, water is forced against the natural concentration gradient and goes from a lower concentration to a higher concentration.

The semi-permeable membrane has very fine pores that are only about 0.0001 microns thick. This is what allows this membrane to catch upto 99% of the impurities from your water supply. Once your water supply has gone through reverse osmosis, the end result is brine and permeate. Brine is the wastewater, whereas permeate is the fresh, clean water for your usage.

What Impurities Does Reverse Osmosis Remove?

Reverse osmosis is very effective in removing a lot of impurities. Reverse osmosis can remove heavy metals such as magnesium, lead, copper, and sodium. It is also very effective at removing chlorine. Furthermore, it can reduce the amount of sulfate, radium, arsenic, and many other harmful elements from your water supply. Reverse osmosis also removes fluoride as well as many herbicides and pesticides from your water. These can be very harmful to your health, and a simple investment could keep you safe.

Advantages of Reverse Osmosis

Some of the benefits of installing a reverse osmosis water filter are as follows:

Effective Removal of Impurities

RO water is free from 99% of the impurities. It is also efficient at removing salts. The semi-permeable membrane further isolates bacteria, viruses, and protects you against waterborne diseases. Furthermore, you won’t have to worry about heavy metals such as lead, sodium, chloride, and so on. RO water is also free of 98% of total dissolved solids (TDS).

Odor-free Water

RO water is free from volatile organic compounds. These compounds are responsible for bad taste or odor in your water. Ordinary water filters, while effective on impurities, do not usually work on removing the smells. However, the activated carbon filter in RO filters is very efficient at delivering purified water without any after taste.


Reverse osmosis systems are rated for two to five years of performance. However, if properly taken care of, they can last much longer. The sediment filters will need to be changed every six months, whereas the carbon filter will only need replacing once every 12 months. The inner membrane needs to be replaced every 24 months. So overall, this filter requires low maintenance and is highly durable.

Disadvantages of Reverse Osmosis

  • Water wastage in the form of wastewater.
  • Depletes some good minerals in the water.
  • It can result in some health problems due to a lack of required minerals.

Water Distillation

Water distillation is a purification process that has been used for a very long time. It functions on the basic principle of the natural water cycle. The first step involves the boiling of impure water. The steam is then condensed to collect pure water. This process is seen to be effective as it removes 99.9% of impurities.

What Impurities Does Water Distillation Remove?

Water distillation has a slightly higher efficiency than that of reverse osmosis. Furthermore, it works on hard water and can remove soluble mineral impurities from water. It can also remove heavy metals like lead, mercury, and arsenic from your water supply. Distillation can target a wide range of pesticides and herbicides as well. Not only this, but they also remove bacteria, dissolved solids, nitrates, and many more unwanted elements.

Advantages of Water Distillation

Some of the advantages of water distillation are as follows:

Excellent Removal of Impurities

Water distillation is a process that has been around for a while, and it is so for a reason. Removing a very wide range of soluble as well as organic impurities, distillation makes sure that you are supplied with pure water.

Mineral and Additive-free Water

Water distillation also works to remove the hardness of water to a certain extent. This highly effective method ensures that you receive pure water free of any additives. With no unwanted minerals, you can get clean water.

No Need to Boil Water

Unlike reverse osmosis, water distillation removes harmful microorganisms from your water supply. This means the water you get can be consumed directly. You won’t need to boil it further.

Disadvantages of Water Distillation

It is not designed to remove chlorine from your water.
Impurities with a lower boiling point than water will not be removed.
It can cause organic impurities to become more concentrated in your water.
It is expensive compared to an RO system.
It requires electricity to function.

Reverse Osmosis or Distilled Water

Some commonly asked questions when it comes to comparing RO and distilled water is regarding their usage. Which type of purification has a better edge over the other? This is why we have come up with a comparison on which water is better suited for the following settings.

For Aquariums

When it comes to aquariums, a slight difference can cause a large imbalance in their ecosystem. Pure distilled water is not ideal for most fishes. Furthermore, it will cause the salts in their blood to diffuse into the water.

Another important thing to note is that your water should not have any chlorine in it. Any chlorine in your aquarium is likely to kill the lifeform in your aquarium. Tap water should be just fine for your aquarium. However, if your tap water has known impurities, then you can use distilled or RO water and add the necessary salts to it.

For Plants

For plants, you can use either distilled water or RO water. However, the comparison should be between hard water and distilled or RO water. Hard water is full of mineral impurities like magnesium or calcium salts.

The type of water that would be suitable for the plant depends on the plant itself. Plants like broccoli, carrot, cauliflower need acidic water. Similarly, plants like nicotiana, iris, dianthus, clematis, and so on prefer alkaline soil. For plants that prefer more acidic water, you can use distilled or RO water.

In case you are growing your plants hydroponically, both distilled or RO water can be a great choice. Hydroponics is basically a subset of hydroculture, where the roots of your plants are in constant contact with water. You might need to add some extra calcium or magnesium to this water to support your plant growth.

For Humidifiers and Batteries

A common mistake people make when using humidifiers is using tap water. As your humidifier breaks up the water particles, it can distribute these mineral impurities into your surroundings. This distribution further promotes bacterial growth. This is why you should always use distilled or purified water for your humidifiers.

Similarly, for batteries, the most commonly used type of water is distilled water. RO water and deionized water is also a frequent choice. Tap water should be avoided as much as possible, as it adds a lot of unnecessary impurities.

In summary,

There isn’t really one purification system that is superior to the other. Both reverse osmosis, as well as distilled water, have their pros and cons. In reality, each of these systems targets different impurities. Depending on your purposes, you should select one that suits you best.