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How Reverse Osmosis Water Filtration Works


To understand how reverse osmosis works, we must understand the principles of osmosis and how it explains the action water naturally wants to take. Recall the lesson we learned in junior high science class: water wants to find its equilibrium.

Say we have a cup. Inside the cup, we have a thin piece of waterproof clothing dividing it into two equal sections. We’re going to call this our “semipermeable membrane.” We fill one half of the cup with saltwater and the other half with the same amount of fresh water.

Suddenly, the water level on the side that contains saltwater will rise because the fresh water moves through the membrane to the highly concentrated solution (saltwater). The water movement is an attempt by the water to have both sides of the cup contain the same ratio of salt.

The water in the cup is finding its equilibrium.

For reverse osmosis water filtration, we simply add pressure to this equation and replace salt with common water contaminants.

What Is Reverse Osmosis Filtration?

Reverse osmosis happens when pressure is used on a highly concentrated solution (contaminated water), forcing the solution through a membrane to a lower concentrated solution (uncontaminated water).

This leaves you with two solutions of water. One that is highly concentrated with contaminants that will wash away down the drain and another solution of uncontaminated water that’s ready for consumption.

The key to effective reverse osmosis filtration is the semipermeable membrane. The semipermeable membrane removes inorganic solids such as salts from water as well as lead and other harmful chemicals.

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6 Steps to the Reverse Osmosis Water Filtration Process

  1. The water from your city’s municipal center or well enters your home
  2. Water enters RO system’s carbon sediment prefilter
  3. Pressurized filtered water moves to the RO membrane
  4. The processed water moves to the storage tank and leftover water with dissolved solids drains away
  5. Once the faucet is activated, water from the storage tank flows through an activated carbon postfilter
  6. RO filtered water flows from the faucet

How Is Reverse Osmosis Different From Traditional Filtration?

What differentiates reverse osmosis filtration from traditional techniques is the presence and power of the membrane. The rate at which the water passes through the membrane allows for pure H2O to flow from your faucet.

Traditional filtration methods rely on a stand-alone substance to eliminate contaminants. Here is a general list of filtration materials you will see in water filters. They all have different advantages and disadvantages, but they all agree that their style of filtration is best for your home.

Activated Alumina
Removes fluoride, but could make water taste metallic

Activated Carbon
Inexpensive and removes chlorine, but can’t remove dissolved inorganic compounds

Ceramic Filters
Cheap and simple, but extremely slow

Ultraviolet Purifier
Eliminates bacteria, but expensive and increases your electricity bill

Water Distillation
Removes contaminants and bacteria, but takes hours to work and requires electricity

Reverse osmosis filtration systems utilize an activated carbon filter and dispel the leftover dissolved inorganic compounds that can be harmful for your health.

The micron rating scale tells us how much more effective RO filtration systems are compared to traditional forms of water filtration.

What Is a Micron Rating?

The micron rating tells us the average size of the openings in a filter. The higher the micron rating, the larger the substance that can pass through the filter.

Micron is defined as one-millionth of a meter and is a popular unit of measurement in tech and science fields. RO systems remove contaminants that are bigger than .001 microns. Carbon filters remove contaminants bigger than .5 microns.

What Do RO Filters Remove?

RO filters remove a number of contaminants that cannot be seen with the naked eye. The following is what’s removed when passed through the reverse osmosis filtration process:

  • Chlorine
  • Sediment (Dirt, Sand, Silt, etc.)
  • Microbial Cysts
  • Lead
  • Chemicals
  • Dissolved Solids

Experience the difference a reverse osmosis system can make.

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What Are the Benefits of Reverse Osmosis Filtration?

1. Improves Diet

One of the exclusive benefits tied to reverse osmosis filtration systems is that it’s a safe way for individuals on sodium-restricted diets to enjoy tap water. Not only does it produce water that’s safe to drink, but it’s also safe to use while in the kitchen preparing food, cleaning vegetables and boiling water.

2. Flexibility

RO filters are safe to use no matter where your water comes from. Nearly the entire population receives water in one of two ways: from a well or municipal center. Reverse osmosis filtration systems are created to extract dissolved solids that contaminate well water. It also removes excess chemicals that are used to treat water at municipal centers.

3. Convenience

Installing a reverse osmosis filtration system is a do-it-yourself project. The systems are slim enough to fit right under your sink. They also take up little space on the counter with a space-saving faucet design.

The Whirlpool Reverse Osmosis Installation Process

How to Change a Whirlpool Reverse Osmosis Filter

Performing a Whirlpool reverse osmosis filter change requires a new pre-filter/post-filter set and no tools. Here’s how you change a Whirlpool reverse osmosis filter:

  • Turn old filter in the system counterclockwise a quarter turn
  • Once the filter is loose, pull it out
  • Turn the new pre- or postfilter clockwise into the correct slot — “pre” and “post” will be marked on the system
  • Replace the system’s battery so the EZ-Change™
  • Indicator Light doesn’t go out before the next filter change
  • “Purge” the water from the old filters in your tank by allowing the faucet to run for a couple hours

The two encased carbon filters are easily replaceable after six months while the membrane can last two years. However, it’s important to keep in mind the longevity of both the filters and membrane depends on the quality of the water coming from your home’s source.

Whether your water smells fishy or you suspect lead contamination, a reverse osmosis filtration system can provide you and your family with safe, clear and chemical-free water for years to come.

Not Sure if Reverse Osmosis is Right For You? Try EcoPureHome’s Interactive Shopping Guide.

EcoPureHome’s guided shopping experience can help you find the right solution for your home’s unique water needs.

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