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Water Filter vs. Reverse Osmosis


*Reviewed by Ken Christopher, Senior Vice President at Rayne Dealership Corporation

Are you curious about the differences between how water filters and reverse osmosis systems function? While both types of systems are used to reduce the number of contaminants in a sample of water, they function in quite different ways.

By understanding the differences between a water filter vs RO water filter system, you’ll be better informed and positioned to find the water filtration system that is right for your needs. Both reverse osmosis and water filters have advantages that make them ideal for certain applications. However, you may find that you want the benefits of both systems for your home water filtration; in which case, you may choose to invest in a system that combines both filtration methods. Here’s how a water filter differs from a reverse osmosis water system.

What is Reverse Osmosis?

Reverse osmosis (RO) systems use reverse osmosis to dramatically reduce the number of contaminants in water. We will now discuss how reverse osmosis works and what it is.

To fully understand the reverse osmosis process, it is helpful to start with osmosis. Osmosis is a natural process that is critical for our lives and the lives of all living creatures around us. Osmosis is the movement of a solvent through a membrane from a solution with a low concentration of solute to a solution with a high concentration of solute.

The solvent or fluid that passes through a membrane in osmosis is usually water. The membrane must be semi-permeable, meaning it allows some molecules to pass but not others. Solutes are any dissolved substances in the solution on either side of the membrane. Osmosis continues until the solutions on both sides of the membrane reach a state of equilibrium.

Reverse osmosis turns this process completely around. In a reverse osmosis filtered water system, you have a solution with a high concentration of solutes forced across a semi-permeable membrane to a solution with a low concentration of solutes. In reverse osmosis, an external force greater than the osmotic pressure is required to force a solvent across a membrane.

Reverse osmosis is used primarily to reduce the number of contaminants in water, so let’s put the reverse osmosis process in real terms. With an RO water system, you start with water that contains a higher number of contaminants. You force that water through a semi-permeable membrane that allows the solvent (water) to pass through the membrane but not the other contaminants or solutes that are in the original solution. On the other side of the membrane is the solution with a low number of solutes, or rather water with substantially fewer contaminants.

What is a Water Filter?

There are various types of water filters but all are devices that contain one or more filtration media to reduce the number of contaminants in water. One thing you might have noticed at this point is that reverse osmosis seems to filter contaminants from water. Reverse osmosis is a common type of water filtration, so what exactly are clean water filters and how are they different?

It’s important to understand what to look for in a water filter since they use a different type of filtration method to reduce the number of contaminants in water. They also reduce different types of contaminants than an RO system does in some cases. The most common type of filtration media found in water filters is activated carbon. 

The activated carbon used in these types of filters is a special type of charcoal that has been treated with oxygen to increase the surface area of the carbon. How big of a surface area? It is estimated that 1 gram of activated carbon has a surface area of over 32,000 feet. This is important because it is this surface area that attracts and traps contaminants through a process known as adsorption. 

Adsorption is the process through which a solid holds or traps a gas or a liquid. In this case, the porous nature of activated carbon gives it lots of little areas where contaminants are attracted to the carbon and then trapped there.

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How Do These Systems Compare?

Most people want to know whether a water filter or reverse osmosis water filtration system is more effective at reducing the number of contaminants in water. To fully answer this question it is important to understand that these systems are both highly effective at removing contaminants, but that they remove slightly different contaminants.

In general, here’s what activated carbon filters remove from water:

  • Volatile organic compounds (VOCs) and other chemicals. These include solvents, fuel oil, polychlorinated biphenyls (PCBs), dioxins, radon, and even radioactive material.
  • Can remove some herbicides, pesticides, and organic contaminants.
  • Removes disinfectants like chlorine that are used in water treatment.
  • Removes the bad taste and odor in tap water.

Activated carbon filters are excellent at removing organic compounds, but aren’t effective at reducing other contaminants. These include minerals such as calcium and magnesium that cause water hardness, heavy metals like lead, salts, fluorine, or microbes.

RO water systems tend to be effective at reducing these contaminants from water:

  • Salts and nitrates.
  • Heavy metals like copper and lead.
  • Reduces mineral content from hard water.
  • Some organic chemicals like fluoride, which is added to tap water.
  • Protozoa such as Giardia and Cryptosporidium.
  • Viruses like Hepatitis A, Norovirus, and Rotavirus.
  • Effective at removing bacteria such as Salmonella, Shigella, and E. coli.
  • Reduces arsenic.

An RO filter is less effective at removing organic chemicals like Benzene and Toluene, Trihalomethanes (THMs), solvents, and volatile organic chemicals (VOCs). A second thing worth noting about reverse osmosis water filtration systems is that they produce a small amount of wastewater as part of the filtration process. This wastewater carries away the contaminants that have been removed from the water that passes through the system.

Which System is Right For You?

We’ve outlined how both pure water filter and reverse osmosis water filter methods function plus their advantages and disadvantages. If you are still considering the advantages of a clean water filter vs reverse osmosis filtration system, it may be helpful to consider how you are going to use the system and what you are trying to remove.

Have Your Water Tested

It is beneficial to have your water quality tested. You can get a general idea of what contaminants are contained in your tap water by reading the water quality report released by your municipal water supplier. Most community water suppliers will periodically test their water and release their findings once or more a year.

While a water quality report may give you a better sense of what’s in your water, in order to get a real insight into what contaminants are in your water you’ll need to have your water tested. If you’d like to have your water tested at your home, contact Rayne to schedule a water test. Our staff can test your water and tell you exactly which contaminants are in your water supply to ensure you have safe and great tasting water all the time. Understanding which contaminants you need to remove can make the decision about which filtration method you should invest in clear.

Consider Your Use Case

How you plan on using your water filtration system may make one system the obvious choice. Do you simply want filtered drinking water? You may consider a point-of-use option like a reverse osmosis system that can be installed under your sink faucet. These systems don’t take up much space and provide many gallons of fresh drinking water every day. 

Do you want filtration for your entire house? If so, you may find yourself looking at hybrid multi-media systems or whole-house water filtration systems. While reverse-osmosis systems can be found for your entire house, they are more commonly used to provide drinking water rather than as a whole-house solution. 

If you still aren’t sure about water filters vs reverse osmosis systems, you may consider a combination of both. In this situation, you would use a pure water filter using activated carbon installed where tap water is piped into your house, as well as a reverse-osmosis system to provide drinking water at your sink faucet. Alternatively, many of Rayne’s RO systems integrate pre- and post-filtration processes using activated carbon, which removes many of the contaminants that aren’t removed during reverse osmosis. You now may be wondering “How much do water filters cost?”.

Final Thoughts

Weighing the advantages and differences between a water filter vs RO system can be confusing at first. With water filters, water passes through one or more physical filtration media to reduce the number of contaminants. Typically these systems rely on granulated activated carbon, which has an enormous surface area that allows it to trap contaminants. Activated carbon filters are excellent at reducing organic compounds and chemicals in water, and reducing the bad taste and odor in tap water.

In contrast to pure water filters, reverse osmosis systems force contaminated water through a membrane that has very small pores. These pores keep most contaminants out of the filtered water that is produced on the other end.

Do reverse osmosis water filters remove minerals and are they as effective as pure water filters? Reverse osmosis filtration systems are very effective at reducing a wide range of contaminants, including salts and nitrates, bacteria, protozoa, viruses, arsenic, heavy metals, and minerals. Either way, choosing a pure water filter or a reverse osmosis filter is a great step for water purification and keeping harmful contaminants out.

Still curious whether to choose a reverse osmosis water filter or a pure water filter? If you aren’t sure which type of filtration system is right for you, consider having your water tested by one of our professional staff at Rayne Water. Water testing can tell you which contaminants are in your tap water supply. This can help guide you towards the system that will be most effective for your particular needs to give you gallons of purified water every day. To schedule a water test, please contact Rayne Water today.

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Expert Reviewer – Ken Christopher