Reverse Osmosis vs Distilled Water: What’s the Difference?

Reverse Osmosis vs Distilled Water: What's the Difference?

Do you know the difference between reverse osmosis and distilled water?

Reverse osmosis and distillation are two different methods for purifying water. Reverse osmosis uses pressure to filter water through a membrane to remove impurities. Distillation separates the contaminants from water by boiling, evaporating, and condensing the purified water.

So which process is better? Deciding between reverse osmosis or distillation can be confusing. It really depends on why you’re purifying your water and what you want to use it for.

In this article we discuss important factors like taste, cost, and health benefits of each treatment method. We review the effectiveness of each method to remove problematic contaminants. We also help you decide which process is better for your plants, aquarium, and humidifier.

Continue reading to learn about the difference between RO and distillation.

Related article: Does Distilled Water Have Fluoride? Yes Or No

What Is Reverse OsmosisWhat is Reverse Osmosis

Reverse osmosis (RO) is a process that forces water through a semi-permeable membrane with pressure to remove contaminants. The RO membrane has tiny holes, known as pores, to allow pure water molecules to pass through while rejecting undesirable substances. The contaminants that can’t pass through the membrane are concentrated in a solutions called brine. The brine waste is discharged down the drain.

Reverse osmosis can be used for potable, industrial and wastewater applications.

Most reverse osmosis systems are designed for Point of Use (POU) applications such as faucet mounted, under sink and countertop models. You can also get a whole house, or point-of-entry (POE) system that connects to the main water line.

How RO works

The heart of a reverse osmosis filter is the membrane. Most RO membranes are a thin film composite (TFC) material that removes contaminants by using pressure to push water through the semi-permeable material. The pores in the membrane are so small it allows pure water molecules to pass through while rejecting undesirable substances like chlorine, VOCs, fluoride, bacteria and pharmaceuticals.

The RO process uses multiple stages of filtration to remove contaminants. The membrane is the heart of the system, but there are also pre-filters and post filters that work together for optimal performance. You’ll need to make some plumbing modifications in your home, but they’re relatively simple and inexpensive.

The first stage in an RO filter is a sediment filter (pre-filter) which removes suspended particles like dirt, sand, clay and rust from water.

Second is the activated carbon filter (pre-filter) which removes chlorine, bad tastes and odors, and VOCs.

The third stage is the RO membrane which removes impurities down to a molecular level. The fourth stage is the post filter which polishes water for better taste.

Contaminants removed by reverse osmosis

The process is effective in removing:

  1. Sodium
  2. Aluminum
  3. Iron
  4. Lead
  5. Fluoride
  6. Chlorine
  7. PFAS
  8. Nitrates
  9. Phosphate
  10. Arsenic
  11. Bacteria and viruses

Interested in a reverse osmosis system? Here is one I installed under my sink.

Check Pricing on Amazon

What is DistillationHow distillation works

Distillation is an effective way to purify water. When you boil water, steam separates from the liquid as the water evaporates. The vapor is collected and condensed as pure, distilled water. The contaminants are either left behind as solids (or a concentrated brine) or evaporate and discharged as a gas.

Distilled water is used for many applications including industrial, medical and personal use such as drinking or growing plants. Some people refer to distillation systems as distillers or water distillers.

How distillation works

Distillation works by heating water to its boiling point where it evaporates into steam. The vapor is collected and cooled in a condenser, which turns the steam back into pure liquid distilled water. Many humidifiers recommend distilled water.

Distillation removes impurities from water by either leaving them behind as solids or discharging them when they evaporate.

Contaminants removed by distillation

Contaminants removed by distillation include:

  1. Lead
  2. Copper
  3. Arsenic
  4. Fluoride
  5. Chlorine
  6. Nitrates
  7. Phosphates
  8. Bacteria and viruses

Interested in a water distillation system? Here is a popular countertop unit.

Check Pricing on Amazon

Reverse Osmosis vs Distilled Water – Is There a Difference?

Reverse osmosis and distillation are both very effective water purification methods. As noted above, they both remove a wide range of contaminants from water. The answer depends in part on what you’re trying to achieve and why you’re treating your water.

Let’s review some common reasons people treat their drinking water to see which method is better.

1 – Taste

Many people use RO and distillation to remove impurities from their water that don’t taste good. The most common chemical that people complain about is chlorine. Chlorine has a bitter taste and smells like a swimming pool. If taste is your main concern, both RO and distillation will work well to remove chlorine and other impurities from your water.

It is worth noting that both of these methods remove minerals like calcium and magnesium from your water. These minerals provide a nice taste and quality to drinking water, and many people don’t like the taste of RO or distilled water. They describe it as being “flat” or having an “off” taste.

You can use a remineralizer to add back these elements to improve the taste and quality of your treated water.

2 – Cost

An under-sink RO filter costs $200-$300. You’ll also spend about $30-50 per year on replacement filters and membranes. If you’re looking for a more permanent solution, there are whole house RO systems that cost around $3000 and require professional installation.

A countertop distiller costs between $250-$500 depending on the model you choose. It’s a one-time purchase and doesn’t require any replacement parts or supplies. Distillation requires a small amount of electricity to evaporate and then condense your water. This will increase your power bill by about $40-$50 per year.

If cost is your main concern, distillation is the less expensive option.

3 – Health benefits

Both reverse and distillation remove many contaminants from water. Some of these contaminants, like lead and arsenic, can be harmful to your health if ingested in large quantities over time.

If you’re looking for a method that removes the widest range of contaminants possible, both RO and distillation are good options.

Reverse osmosis can remove volatile organic compounds (VOCs) from drinking water, but distillation has limited effectiveness for VOCs. If you are concerned about VOCs in your water, RO is a better choice.

4 – Aquariums

Aquariums require very pure water to thrive and maintain healthy fish and plants. The main issue with tap water is the chlorine it contains. Both RO and distillation remove chlorine and other impurities, making them the ideal methods for treating water for aquariums.

Demineralized water is not ideal for aquarium use. As a result, you’ll need to add minerals back to the water using a remineralizer. If you skip this step, your fish and plants will suffer from mineral deficiencies that can lead to serious health problems and even death.

For aquariums, reverse osmosis and distillation are equally effective.

5 – Plants

The type of water that is best for plants depends on the type of plants you’re growing. Some plants, such as broccoli and carrots, need acidic waters, while others, like iris or dianthus, thrive in alkaline conditions.

RO water is slightly acidic. This makes is more suitable for plants that need acidic water. Examples of plants that do better with reverse osmosis include:

  • broccoli
  • carrots
  • cauliflower

Distilled water has a neutral pH. Plants that do better with distilled water include:

  • dianthus
  • clematis
  • iris
  • nicotiana

6 – Humidifiers

Humidifiers require demineralized water to work properly. If you use tap water in your humidifier, the calcium and magnesium in the water will leave white deposits on surfaces around your home. These deposits can be difficult to clean and can damage the humidifier over time.

RO and distillation produce demineralized water, making them the ideal methods for humidifier use. Either method is acceptable for use with humidifiers.

7 – Batteries

Batteries require water that is free of minerals and dissolved ions. Most battery manufacturers specify the use of distilled water for their products. You can also use RO water in your battery.

Relative Pros and Cons

Each of these treatment methods – reverse osmosis and distillation – have their benefits and limitations. Let’s review them all to give you a sense of what might be the best choice for you.

Advantages of reverse osmosis water

Reverse osmosis has several advantages that make it an attractive water treatment method.

  • effectively removes many contaminants including VOCs
  • reduces many contaminants by 99%+
  • relatively simple to maintain
  • low to moderate cost of operation
  • removes taste and odor compounds from water

Disadvantages of reverse osmosis

Reverse osmosis has the following disadvantages:

  • removes beneficial minerals like calcium and magnesium
  • produces an “off” taste for some people
  • wastes water, in some cases as much as 3 gallons for every gallon of treated water
  • may require a booster pump if you have low water pressure

Advantages of distillation for drinking water

Distillation is an effective treatment method that offers the following benefits:

  • removes many contaminants
  • effectively reduces the concentration of most contaminants by 99%
  • easy to set up and maintain
  • low cost of operation

Disadvantages of distillation

Distillation has the following disadvantages:

  • requires more energy than RO to operate
  • produces demineralized water that may be harmful for aquariums and plants unless remineralized
  • does not remove volatile organic compounds from your water


Is reverse osmosis the same as distillation?

Reverse osmosis and distillation are two different methods of water treatment. While they both produce clean, contaminant-free water, the processes by which they do so are quite different. Distillation uses evaporation followed by condensation to purify water. RO uses a membrane to filter contaminants out of water.

Is it safe to drink RO water?

Reverse osmosis water is filtered and devoid of volatile chemicals. The water produced by reverse osmosis systems is safe to drink. However, the process removes beneficial minerals from your tap water. If you want to consume these minerals, you can remineralize your RO water before drinking it.  RO (reverse osmosis) filtered water tastes better since the process is consistent and reliable.

Is water distilled or filtered water better?

The question of reverse osmosis vs distilled water is one many of us ask. Both distillation and reverse osmosis are methods of water purification. They each have relative benefits and limitations, so you should read this article to decide which method is better for your needs.

Is boiling water the same as distillation?

Distillation and boiling are two different methods of water purification. Distilling uses evaporation to separate contaminant particles from the liquid, then condenses the vapor back into a usable form. Boiling involves bringing your drinking water up to 212 degrees Fahrenheit until all contaminants are killed off or sanitized.

What can I use distilled water for?

You can use distilled water for any purpose where you need clean, contaminant-free water. Distilled water is especially useful if your tap water contains a high concentration of dissolved solids or minerals like calcium and magnesium.

Should I switch to bottled water?

Many people drink bottled water because they believe it is safer and better than filtered water. Much of the bottled water available today is just reverse osmosis water. In addition, using RO and distilled water filters is much cheaper than buying bottles every day.

Final Take

Choosing the right water treatment system for your needs can be confusing, but it doesn’t have to be. Reverse osmosis and distilled are two different types of purification systems that many people use in their homes. Distillation and RO filters both remove hard minerals. Reverse osmosis and distilled water are both pure and safe to drink.

This article makes deciding between the two processes easy. It explores the relative pros and cons of each method, explains how they work, identifies differences that may make it better (or worse) for your needs. It also answers frequently asked questions about RO and distillation.

By the time you finish reading, you’ll know which process is better for your needs. You’ll have peace of mind that you’re making a good choice by choosing the right water treatment system.

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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