What is Reverse Osmosis? The Complete Beginner’s Guide


Let’s start out with a by the book definition of reverse osmosis:

Reverse osmosis is a water purification process wherein water meant for drinking is passed through a system that utilizes a semipermeable membrane to remove, ions, molecules, and other larger impurities and particles from the water, rendering it drinkable.

That might be a lot for you to take in. Don’t worry, the aim of this article is to break it all down for you in an easy to understand manner. The long and short of it is that during reverse osmosis, water of questionable quality goes in and clean, crisp, and completely safe water comes out.

To understand reverse osmosis fully, you must first understand, you guessed it, osmosis itself. Osmosis is a naturally occurring process wherein a weak saline solution wants to move and combine with a strong saline solution. In other words, from freshwater to saltwater. It’s the job of the semipermeable membrane to make sure that only certain substances are allowed through.

The simple version of this system is found almost anywhere you look, from roots in plants to our very own bodies. Reverse osmosis does exactly the opposite. It applies pressure on the side of the strong saline water (or in this case the impure water), forcing it through the membrane in the opposite direction and resulting in the demineralized, deionized and decontaminated water you get to drink.

What Are The Benefits Of Reverse Osmosis?

Let’s get right to the meat of it. If you are looking for a reverse osmosis system it means you want cleaner, safer drinking water. But what does that actually mean? What is in our water that we need reverse osmosis to purify it and make it potable? Let’s find out!

Reverse Osmosis Gets Rid Of All Kinds Of Unwanted Contaminants

Water might always look crystal clear when it comes out of the tap but it would surprise you just how many solids are actually present. Excellent reverse osmosis equipment should be certified to get rid of the majority of these particles, leaving you with smoother, cleaner, and safer drinking water.

Here are some of the contaminants you can expect your reverse osmosis to remove:

  • Lead
  • Fluoride
  • Nitrates
  • Arsenic
  • Copper
  • Chromium
  • Selenium
  • Cyst
  • Radium
  • TDS (total dissolved solids)
  • Barium

You might have heard a lot of concern around the health impact around drinking demineralized water, you shouldn’t be too alarmed. In the end, it depends on your individual lifestyle. In a perfect world, we would get all these minerals from our daily nutrition. For many, mineralized water is an important supplement.

However, there is no doubt about all the bad stuff that is removed during the reverse osmosis process. If you want pure, clean, and water that doesn’t taste funny reverse osmosis is the best option for you.

Improves Taste

Many of the contaminants listed above can lead to a bad or funny taste in your drinking water if present in disproportionate amounts. Reverse osmosis provides that crisp and refreshing taste that so many of us long for when we are thirsty or on a hot day.

Saves Money

If you are relying on bottled water for your clean water, you could cut down on a regular expense. When you have a reverse osmosis system there is no need for bottled water. You will be making water that’s just as clean at home. In fact, some friends and family might come to you to bottle water.

Simple Maintenance

A lot of times the thing that makes or breaks someone’s decision to buy a system like this is the hassle involved with maintaining the equipment. However, reverse osmosis systems tend to be very easy and inexpensive to service and maintain.

Reverse Osmosis: Step By Step

Stage 1: Prefiltration

If you want a long-lived and healthy filtration system, this step is absolutely paramount. During the prefiltration phase, anything that could cause build-up or blockages in your reverse osmosis system is filtered out. In other words, it does exactly as the name suggests.

Some of the culprits that are filtered out during this stage include silt, rust, and scale. Filtering out these materials protects your system’s membrane and automatic shut-off from clogging up with debris. This, in turn, keeps your reverse osmosis system ticking like clockwork.

In systems that make use of a T.F.C. (thin-film composite) membrane the prefiltration unit should also consist of activated carbon. On top of filtering out all the above debris, it also filters out carbon particles that damage T.F.C. membranes as well as other contaminants not picked up by normal filters.

Stage 2: The Membrane

Now the water passes through the HQ of the reverse osmosis system where the magic happens. The semipermeable membrane only lets the water and certain other substance pass based on their size and traits, such as whether they are ionic.

Just the right amount of pressure is used to force the solvent (water with impurities) through the membrane. In nature and normal circumstances, the solvent would move from a state of low solute concentration (high water potential) to a high solute concentration (low water potential).

By using external pressure to reverse this process, reverse osmosis gets its name. This is also what makes it different from simply filtration. Filtration only blocks particles based on their size, whereas reverse osmosis uses diffusion.

The semipermeable membrane only let’s Hydrogen and Oxygen molecules through, which leads to pure H2O. The remaining water now holds most of the original dissolved solids and contaminants and is drained out of the system.

Stage 3: Clean Drinking Water

The water then passes to a holding tank, where it waits for you. It’s the automatic shut-offs job to let the rest of the system know when the holding tank is full and when more water can be purified.

If you think that’s where it ends though, you would be wrong. Before flowing into your glass, the water goes through a final filtration process, just to make sure that it’s completely odorless and that there are no bad tastes left. This done through the use of a carbon filter.


How Much Power Does A Reverse Osmosis Unit Use?

None! Reverse osmosis units run completely off of water pressure so no power is necessary.

Is The Demineralized Water Bad For My Health?

While it might lessen your intake of certain minerals marginally by consuming water that has gone through reverse osmosis, it’s not in itself detrimental to your health. As part of a healthy, well-balanced diet you should get in most of these minerals already. It’s further been argued by many experts that the form in which these minerals are present in water is hard for your body to utilize in any case.

How Regularly Do I Have To Service My Reverse Osmosis Machine?

Except for the membrane, that only has to be replaced every 2-3 years, the pre- and postfilters in a reverse osmosis systems only have to be replaced every 6-12months.

How Long Will My Reverse Osmosis System Last?

Typically, good quality reverse osmosis machines from reputable brands last anywhere from 10 to 15 years. So it’s really a long-term investment and you definitely will recuperate your costs from being dependent on bottled water. This does, however, depend on you well you take care of your machine and whether you regularly service it on time.

Is It True That Reverse Osmosis Wastes A Lot Of Water?

Unfortunately, it’s true that reverse osmosis machines drain away more saline water than it purifies. However, for typical consumption over a monthly period, this won’t cause a noticeable increase in your water bill.

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