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What Is Reverse Osmosis and How Does it Work?

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What Is Reverse Osmosis and How Does it Work?

Somewhere along the course of your life, you might have heard of a water filtration process known as reverse osmosis. This is a process which produces some of the healthiest drinking water you could ever dream of. For some, it's seen as a great alternative to buying bottled water.

Looking to learn a little more about reverse osmosis? Interested in knowing how it works? This article has everything you need to know.

Components in a Reverse Osmosis System

To help it function sufficiently, a reverse osmosis system contains a variety of different components. These components include everything from valves to filters, to structural components, and more.

Below, we'll discuss them all in detail.


The component which holds all of the internal components together is the casing. This component protects the internal components from external physical trauma, ensuring that they're always able to function at their maximum capacity.

Feed Valve

The feed valve is the part of the RO system which connects the system to its corresponding water supply.


The first filter which the water supply will meet is the pre-filter. This filter removes any large contaminants which may exist within the water. Examples of large contaminants include sediment, sand, and dirt.


After the water has passed through the pre-filter, it will meet with the heart of the RO system, the membrane. This component is responsible for filtering the majority of dissolved contaminants which exist within a water supply. Dissolved contaminants include chloride, arsenic, cyanide, iron, calcium, and much, much more.


The post-filter is essentially the clean-up crew for the membrane. Its job is to filter out contaminants which the membrane might have missed.

Storage Tank

Once water has been fully filtered, it will be dumped into the system's storage tank. The storage tank holds water until the user is ready to consume it.

Automatic Shutoff Valve

The automatic shutoff valve is a valve which becomes triggered once its corresponding storage tank is completely filled. Without this valve, the reverse osmosis system would waste substantial amounts of water and energy.

Drain Valve

Not all of the water which passes through an RO system will be filtered. Water which goes unfiltered will be drained from the system with the help of its drain valve.


The faucet of a reverse osmosis system is quite simply the component which delivers fresh, purified water.

How Does Reverse Osmosis Work?

All reverse osmosis systems work just a little differently from one another. Whereas some utilize only 2 stages of filtering, others utilize 3, 4, or even 5. In this article, we're going to describe how a 4-stage system operates.

Stage 1: Sediment Filtering

The first operational stage of a reverse osmosis system is the sediment filtering stage. At this stage, large, slightly-visible contaminants such as dirt, dust, sand, and stone will be removed from the water.

If you get your water from a municipal water supply (generally free of sediment), this stage won't make much of a change. However, if you get your water from a well (sediment-dense), it's hugely important. After all, well water is almost guaranteed to have some dirt, dust, or stone contained within it.

Stage 2: Large Dissolved Mineral Filtering

The 2nd stage of a 4-stage system will involve the filtering of largely dissolved minerals. These minerals include everything from calcium to iron, to magnesium, to manganese, and more.

Though this filter won't eliminate all of the largely dissolved minerals in your water, it will remove a great deal of them, preparing your water for the biggest filtration stage there is--the membrane stage.

Stage 3: The Membrane

As was noted above, the membrane is the heart of the RO system. It is responsible for filtering out between 95% and 99% of the dissolved minerals which exist within your water supply. It will remove everything from chloride to arsenic, to sodium, to calcium, and more.

Once the water has passed through the system's membrane, it will be almost 100% purified. However, it's not yet finished. There is still one more stage it must go through--post-filtering.

Stage 4: Post-filtering

The post filter is typically a carbon filter. It removes most small traces of contaminants which may still be remaining in your otherwise purified water. By doing this, it generally voids your water of all unsavory tastes and smells.

Contaminants which may be removed in this stage include chlorine, fluoride, iron, and calcium, to name just a few.

After the water has been sent through the post-filter, it will be dumped into the storage tank. There, it will wait until it's pumped up for consumption.

Advantages of a Reverse Osmosis System

Reverse osmosis systems offer a number of different advantages. Two of the primary advantages of these systems are as follows.

Incredibly Pure Water

If you're looking for incredibly pure water, a reverse osmosis system is exactly what you need. These systems will rid your water of almost all potential contaminants, making it as healthy, and as appetizing as possible.

In addition to removing large minerals such as magnesium, iron, and calcium, reverse osmosis systems will also remove chemicals such as fluoride, chloride, and cyanide.

Cheaper than Bottled Water

The fact of the matter is that, in the long run, reverse osmosis systems are incredibly inexpensive. While they can be expensive upon initial installation, they cost close to nothing to maintain. Utilizing very little electricity, they don't affect your energy bills in any remarkable way.

Because of this, they are a terrific alternative to bottled water. In fact, it has been found that consumers spend around 300 times more on bottled water than they would otherwise have to spend on tap water.

Looking for More Water Filtration Information?

Are you in search of further information on water filtration systems? Thinking about purifying the water in your home or commercial building? Water Filter News has you covered.

Our site has tons of info on all things water filtration. Whether you're thinking about installing a reverse osmosis system, a water softener, a chemical injection system, or otherwise, we can help you to make a final decision.

Have any questions? Contact us right now!

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