Reverse Osmosis: Why is it great and how does it work?

Reverse osmosis is a water purification process used around the world for clean, delicious water. It’s widely regarded as one of the most efficient and well-rounded filtration systems available.

For areas with unsafe drinking water, this process can actually save people’s lives and prevent serious illness. However, even for locations with relatively safe water, heavy metals can leach in from old pipes, and so-called “forever chemicals” have found their way into most of the world’s water, even contaminating our rainwater. Reverse osmosis removes all of these hazards, and more.

How does it work?

To understand what reverse osmosis is, it’s helpful to know how regular osmosis works. Simply put, osmosis is a natural process where low concentration water (concentration refers to the amount of particles in the water), passes through a semipermeable membrane, into higher concentration water. The result is that the water concentrations equalize.

With reverse osmosis, the opposite happens. Energy is used to create pressure, which forces the high concentration water through the membrane and into the lower concentration water. The contaminants are then blocked by the filter, resulting in purified drinking water?

What are the benefits?

The main benefit of reverse osmosis is how effective it is at filtering out a wide range of toxins and impurities, when compared to other filtration systems. This process can filter out contaminants as small as 0.0001 microns in size, which means it easily eliminates viruses and bacteria like E. Coli, Hepatitis A, and Salmonella, which other filtration systems can’t do.

It also effectively removes up to 99.9% of common hazardous chemicals, including dangerous heavy metals like lead and mercury. Additional benefits include overall improved taste and odor, since the process removes unpalatable chemicals such as chlorine and sulfur as well.

The four stages of filtration

The process usually consists of four filtration stages, each working together to remove everything from visible sediment to microscopic viruses.

Stage 1

The first step of the process is a sediment pre-filter, which acts like a strainer to remove larger particulates like dirt, dust, algae, and other debris from the water. Eliminating these larger particles in the beginning, prevents a lot of wear and tear on the more delicate filters in later stages.

Stage 2

Stage two consists of an activated carbon pre-filter. Chemicals like chlorine and chloramines, which effect the taste and smell of the water, are removed during this level of filtration.

Stage 3

Reverse osmosis is the third and most essential part of the filtration system. The water is forced through a semipermeable membrane, usually made of biodegradable cellulose acetate, which eliminates up to 99% of bacteria, viruses, and dissolved solids. It also softens the water, leaving it almost entirely free of all unwanted particles.

Stage 4

The final stage is a second carbon filter, also referred to as a polishing filter. This step is mainly used to put the finishing touches on the overall taste and odor of the water. Any residual chlorine that made it through the previous steps will be removed here.


Due to its effectiveness, reverse osmosis also removes many useful minerals such as magnesium and calcium, which we want in our water.

To counteract this, minerals are added back into the water after the four-step process, for both health and taste purposes. In the end you’re left with all the benefits of healthy, great-tasting drinking water, minus the toxins.

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