What is Reverse Osmosis

Reverse osmosis is one of the most effective methods of filtering the tap water in your home. Reverse osmosis technology is designed to remove a great percentage of the contaminants in your drinking water by filtering the water through a semipermeable membrane.

Reverse osmosis filters are one of the main types of water filters trusted by commercial businesses and private homeowners alike. Reverse osmosis filtration systems are among the most popular options because of the large amount of potential contaminants that the process removes. Other types of popular water filters include UV filters, infrared filters, water ionizers, and carbon filters. Many technologies within these types of filters overlap - for example, our 6-stage reverse osmosis water filter contains a carbon filter, and deionizes tap water in a manner similar to that of other filters.

How does Reverse Osmosis Work?

At its most basic, reverse osmosis is a process through which inorganic solids, like salts, are removed from an aqueous solution, like your tap water. The water in your tap is pushed through a semipermeable membrane, which filters out many contaminants and impurities that can find their way into your drinking water.

“Reverse osmosis” can often sound like scientific jargon, so let’s break down that phrase to demystify the actual process. First, we should outline the natural process of osmosis as it occurs in nature.


Osmosis is one of the most important processes to occur in nature every day. Osmosis occurs when weaker saline solutions migrate to stronger saline solutions. Or, put simply, when water with fewer particles or impurities moves naturally to adjacent water with more particles and impurities. An example of this in the real world is when your kidneys absorb water from your bloodstream - the water in your blood moved to the denser area of your kidneys.

diagram of osmosis

Less concentrated solutions will always migrate to more concentrated solutions if possible. A semipermeable membrane allows small particles like water to pass through, so if you separated a solution with low salt content and a solution with high salt content by placing a semipermeable membrane between them, the solution with low salt content would pass through the membrane and fill the solution with high salt content until their densities were equal.

Semipermeable Membrane

What, exactly, is a semipermeable membrane? The technical definition is a barrier through which some particles can pass through, but others cannot. Some great examples in real life would be a sponge, a fisher’s net, or a screen door. While air can flow through your screen door, a bird certainly could not.

Reverse Osmosis

So, then, reverse osmosis is exactly that: reversing the process of osmosis to push solutions with a higher concentration of particles through a semipermeable membrane to remove unwanted particles and contaminants. Because of the way the process works, a particle’s size determines whether or not it will remain in your tap water once it’s pushed through. Some reverse osmosis filters can remove particles that are as small as .001 microns.

diagram of reverse osmosis

How can the process of osmosis be reversed? By applying concentrated energy to the solution (in this case, the tap water being directed into the filter). Reverse osmosis filters like those sold by Pelican Water apply a great deal of energy to your tap water to pass the water through a semipermeable membrane and remove the contaminants within. This process will desalinate the water and block many contaminants from remaining in your water. The process of desalinization (removal of salt) can also be referred to as demineralization or deionization (removing minerals or certain ions from your water).

Multiple processes occur within a reverse osmosis filter that leave you with crisp, refreshing drinking water with most impurities removed in a matter of moments.

What Does Reverse Osmosis Remove?

As we touched on above, the process of reverse osmosis does not target impurities or contaminants of a certain type - rather, the determining factor in whether a specific mineral or particle is filtered is size. The semipermeable membrane is so thorough, however, that many common contaminants are removed at rates of 98% or greater. In general, reverse osmosis filters are capable of removing about 99% of all particles, dissolved salts, organic molecules, bacteria, and other harmful contaminants from drinking water.

You may be asking yourself: why do I need a water filter to remove potentially harmful contaminants? Doesn’t my public water system treat my tap water? It is certainly true that your public water system works ardently to remove most contaminants from your drinking water. In general, much of the tap water across the country is safe to drink and contains few impurities. However, many impurities listed below are not EPA regulated and can easily find their way into your water supply. That’s why a reverse osmosis system is a wise investment.

Here are some of the most prevalent contaminants filtered out by our reverse osmosis filter:


Arsenic V (pentavalent) 99.0%

Chromium 6 (Hexavalent) 98.3%

Chromium 3 (Trivalent) 99.0%

Barium 98.8%

Cadmium 98.3%

Copper 98.4%

Radium 226/228 98.8%

Selenium 97.9%

Turbidity 98.7%

Cysts › 99.99%

Fluoride 93.8%

Lead 96.8%

TDS (Total Dissolved Solids) 93.10%

Does Reverse Osmosis Remove Fluoride?

Yes! The Pelican Water 6-Stage Reverse Osmosis System removes fluoride at a rate of approximately 93.8%.

Currently, about two-thirds of the U.S. population receives fluoride through their community water system. This was originally implemented to theoretically decrease tooth decay in our children. Some health care professionals listed water fluoridation as one of the ten great public health achievements of the 20th century; in contrast, most European countries have experienced substantial declines in tooth decay without its use, primarily due to the introduction of fluoride toothpaste in the 1970s.

If you brush your teeth with fluoride toothpaste, many professionals believe that ingesting fluoride will not help your dental hygiene, and will in fact cause health problems in high doses. Reducing fluoride consumption is especially critical for infants, for whom fluoride exposure can cause disfiguring dental fluorosis.

While the EPA Maximum Contaminant level is 4 mg/l, the World Health Organization recommends a guideline maximum fluoride value of 1.5 mg/L as a level at which fluorosis should be minimal. The average amount of fluoride in the US city municipalities is 0.7 mg/l to 1.2mg/l, but this can vary based on where you live. If you’re concerned about fluoride in your water, the 6-Stage Reverse Osmosis System from Pelican Water will reduce to the amount of fluoride in your water by 93.8%, to a rate that is safer for adults and infants alike.

Does Reverse Osmosis Remove Chlorine?

Yes! The carbon filter in our 6-Stage Reverse Osmosis System reduces the chlorine in your tap water eliminating the taste and odor.

Many reverse osmosis systems, like ours, is a multi-stage filter that contains multiple filters to better treat your water. A sediment filter removes small sediment and dirt to protect the entire system. A carbon filter removes contaminants such as chlorine that could potentially damage the reverse osmosis membrane.

Chlorine is a very popular disinfectant that is utilized in public water treatment to remove waterborne viruses, bacteria, and protozoa for decades. While this is an important benefit of its use, homeowners often do not want chlorine present in the tap water they drink or bathe with due to its strong odor resembling bleach.

In addition to its unwelcome odor, chlorine should be removed from your drinking water because it can react with organic matter in your water to form toxic byproducts called trihalomethanes (THMs). Unsafe to be consumed, THMs are linked with higher probabilities of developing bladder, colon, and rectal cancer. Luckily, many RO systems include carbon filters which can greatly reduce chlorine, and homeowners can also purchase carbon filter systems separately.

Does Reverse Osmosis Remove Minerals?

The answer here is a little more complex - the 6-Stage Reverse Osmosis filter from Pelican Water does remove many minerals, but actually adds some minerals into your drinking water as well.

Minerals are not inherently bad for you - if you take daily vitamins and minerals for your health, you know that some minerals are important for a strong, healthy body.

Some of the more harmful elements that can be found in your water, like arsenic or copper, are not minerals at all. These types of elements are filtered out in high percentages by reverse osmosis filters.

Some minerals, like sodium (commonly known as salt), do exist in your drinking water and are filtered out by reverse osmosis membranes. The average American’s daily intake of sodium surpasses the recommended limit. Thus, having sodium filtered out by a reverse osmosis filter is beneficial for your wellbeing.

Conversely, essential minerals like calcium and magnesium are greatly beneficial to your health. The mineral filter inside of our 6-Stage Reverse Osmosis System adds an amount of these beneficial minerals back into your drinking and cooking water to promote good health.

Does Reverse Osmosis Remove Coliform Bacteria?

Unfortunately, it does not. While the 6-Stage Reverse Osmosis System removes many contaminants, the system is not designed to completely remove coliform bacteria. It’s important to consider where you’re getting your tap water from when deciding how to treat your water for bacteria like total coliform and E. coli.

As the Centers for Disease Control and Prevention attests, reverse osmosis systems “have a very high effectiveness” of removing many kinds of protozoa and viruses, but this is a by-product of the effectiveness of the system. The process of reverse osmosis does not target bacteria directly.

Well water is more susceptible to bacterial infection. If you use well water at home, test your water periodically for bacteria like E. coli and total coliform. Determining if your water supply is at risk for being contaminated with organic matter is an important step when choosing a water filtration system.

If you are searching for a filter that specifically targets coliform bacteria, invest in a system that meets the EPA’s Guide Standard for microbiological purifiers in order to protect your home from viruses, cysts, and bacteria. Combine your RO system with one of these options from Pelican Water:

Basic UV Disinfection System

Now $642.60

Was $1,298

Learn More

Drinking Water Purification System

Now $442.65

Was $1,198

Learn More

What are the Benefits of
Reverse Osmosis Filtration?

There are numerous benefits of reverse osmosis filter systems. Some of the most compelling reasons to invest in a reverse osmosis filter system include:


Better Health,
Better Taste


Multiple Stage


Heavy Metal

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

If you’re looking into water treatment for your home, you’ve probably heard about water softeners. Pelican Water carries some of the leading water softeners in the industry. So, what’s the difference between a reverse osmosis filter system and a water softener?

A lot, it turns out. First, we should explain what a water softener does.

Water Softener

A water softener does exactly what its name implies: it softens water. But what is “hard” water? Hard water affects more than 85% of water supplies in the United States. It has a high concentration of dissolved minerals like iron, silica and manganese. Water hardness is measured in grains per gallon (GPG), which determines the concentration of minerals dissolved in one gallon of water. Generally, any water supply that has a hardness greater than 3 GPG is thought to be ‘hard’ water. ‘Soft’ water, according to the Water Quality Association, is water that contains less than 1 GPG of the above minerals.

Hard water can cause many problems in your household, including:

Clogged water lines to faucets and refrigerators.

Malfunctioning appliance heating elements as hard water scale builds up.

Reduced effectiveness of soaps and detergents in cleaning clothes and dishes.

A water softener reduces the presence of nuisance minerals like those listed above without removing beneficial minerals like magnesium or calcium. This process softens the water and provides great hard water scale reduction for your piping. Water softener alternatives with salt-free technology like those from Pelican Water can also remove existing hard water scale deposits.

What a water softener does not do, however, is purify your water.

Reverse Osmosis Filter

A reverse osmosis filter system, on the other hand, purifies your water and makes it safer to drink by removing potentially harmful contaminants that can worsen the taste of your water and cause health problems. The minerals targeted by water softeners cause water hardness and scale buildup. If you only install a water softener, you are not treating your water for contaminants like lead, arsenic, and other elements that a reverse osmosis filter system would remove.

While the processes that water softeners and reverse osmosis filters use are similar, the specific targets of each system differ. The two systems are not interchangeable.

Therefore, if hard water is a concern in your home, you should invest in a filter system that contains both a water filter and a water softener, or purchase two compatible systems like the 6-Stage Reverse Osmosis System and the Pelican NaturSoft® Water Softener Alternative.

Pelican NaturSoft® Water Softener Alternative

Now $1,470.40

Was $3,148

Learn More

Top Rated: What’s the Best Reverse Osmosis Filter?

Our best reverse osmosis filter is our top-selling 6-Stage Reverse Osmosis System.

6-Stage Reverse Osmosis (RO) System

Now $301.60

Was $599

Learn More

Satisfied homeowners choose our popular reverse osmosis system for many reasons. In addition to its cutting edge reverse osmosis filtering technology, our 6-Stage Reverse Osmosis System touts the following advantages when compared to similar systems on the market:

Six Stages of Filtration

Many reverse osmosis filters contain four or five stages of filtration. Our system has a four-stage prefilter, membrane and postfilter housed in one cartridge where the primary purification processes occur. The fifth and sixth stages, the in-line carbon filter and calcite cartridge, are housed between the tank and faucet. In these final stages, minerals are added back to the drinking water to create a balanced, pH neutral water for drinking.

Here’s a quick breakdown of how our six stage filtration system works:


Reverse Osmosis removes dissolved solids, chemicals, and contaminants.


RO creates pressure and forces your water through a semi-permeable membrane.


By filtering out impurities, you are left with clean-tasting and delicious water.


Sediments and contaminants collected in the filters are safely flushed down the drain.


Pelican’s Pro RO delivers great tasting water straight out of your kitchen sink.


Essential minerals are added back into the water.

Small and Compact

Our point-of-use reverse osmosis system is much smaller and lighter than most RO systems. It is about the size of a 2-gallon tank, and is less than 14 inches in height. It can usually be installed in a small kitchen cabinet. This makes installation under your kitchen sink completely manageable. You’ll still have space to store your cleaning supplies and typical household items.

Green By Design

The 6-Stage Reverse Osmosis System reduces the amount of water that is released down your drain by 50% compared to other RO systems on the market. In addition, the compact size of our water filtration system means fewer materials are used in the manufacturing and packaging stages. The lighter shipping requirements reduce the overall impact each system has on the environment.

Minimal Maintenance Required

You will need zero tools to maintain the 6-Stage Reverse Osmosis System. The only maintenance required is to remove one cover and replace the cartridge inside the system. Homeowners should change the 2-stage post-filter every 6 months and switch out the 4-stage membrane every 18 months. If you sign up for our Watershield Autoship Club, the replacement filters for your system will be automatically be shipped to you at the appropriate time. You won’t even need to remember!

More Water Filtered Per Day

The semipermeable membrane of the 6-Stage Reverse Osmosis System can filter up to 50 gallons of water per day, which quickly refills the storage tank. This means that our filter delivers approximately 30% more water flow from your faucet than other RO systems.

Reverse Osmosis Facts


Reverse osmosis is not the same process as water distillation. During distillation, water is heated to produce steam, then the resulting steam is condensed to reform water. This creates technically purer water, but water that results from distillation is also free of beneficial minerals like calcium and magnesium. Reverse osmosis, on the other hand, filters the water through a semipermeable membrane without converting it into steam.


Reverse osmosis does not reduce every type of particle or contaminant. Only particles that are larger than the openings of the semipermeable membrane can be effectively reduced. While reverse osmosis does protect against many dangerous chemicals, many consumers assume that it wholly protects homeowners from microorganisms like bacteria. This is only partially true. Many bacterial and viral organisms are too small to be eliminated with RO systems alone. We recommend an additional UV water filter if this is a concern.


Reverse osmosis does reduce some healthy minerals. Many types of minerals are reduced when reverse osmosis is used, including sodium, iron, lead, manganese, and calcium. Many of those minerals are dangerous, and their absence in your water is beneficial. However, your body benefits from some of these minerals, including calcium. Because of this, our 6-Stage Reverse Osmosis independently adds healthy minerals back into your water once the reverse osmosis process is complete.