Reverse Osmosis vs. Carbon Filters

We put reverse osmosis and carbon filtration to the test.

By: Alyssa Scavetta

Are you looking at water filters but confused about the differences between reverse osmosis and carbon filters?

These are some of the most popular water filters available to consumers and each has their own unique advantages and disadvantages. To help you make an informed decision about which is right for your home, we’ve compiled crucial information about these types of water filters.

Learn how reverse osmosis and carbon filters work, plus the benefits and drawbacks of each in addition to some helpful information about the certifications you should look for before purchasing a filter for your home.

what is reverse osmosis

Reverse osmosis (RO) is a process of separation that uses intense water pressure to force the source water through a semipermeable membrane that retains the solid contaminants on one side while allowing clean water to pass on to the other side.

In English? It’s like a mosquito net. It lets the water flow through the membrane while blocking out objects that are too big to pass through. That’s why this process is effective at removing anything bigger than a water molecule including common contaminants such as lead, asbestos, chlorine, and several others.

In English? Reverse Osmosis is like a mosquito net. It lets the water flow through the membrane while blocking out objects that are too big to pass through.

Benefits and Drawbacks of Reverse Osmosis Water Filters

The main advantages of reverse osmosis include its ability to remove more contaminants than other filtration methods, the ability to filter water down to a sub-micron level, and the fact that it provides the best water for cooking which is why its become popular among chefs.

So, what about the drawbacks?

During the process, RO systems produce quite a bit of wastewater; a typical system has a ratio of about 4:1. That’s four gallons wasted for every gallon of clean water produced. There are “zero waste” systems which use electricity to force water through the RO membrane or recycle wastewater, but this puts wear and tear on your system meaning you’ll have to replace filters more often.

Additionally, RO systems are so effective at removing solids that they also tend to remove healthy minerals that your body needs including calcium, potassium, and magnesium. To address this, Aquasana’s Aquasana OptimH2O® Reverse Osmosis + Claryum® Filter utilizes remineralization technology to retain these beneficial minerals and restore water to a good pH balance.

How do carbon filters work?

Most filters on the market use carbon filtration technology to retain contaminants inside your filter, preventing them from flowing through your tap. Carbon filters rely on the process of adsorption, in which the filter acts like a magnet — allowing contaminants to collect on a large surface area where molecules exert force for other molecules to attract to. The longer the water stays in contact with the carbon media, the more contaminants can be absorbed from the water.

There are two main types of carbon filters on the market, including:


  • Activated CarbonThe majority of water filters you’ll come across use an activated carbon media made from coconut shell, coal, or wood. These filters are incredibly porous and a single teaspoon has more surface area than a football field enabling it to remove contaminants through adsorption.
  • Catalytic CarbonCatalytic carbon is actually a class of activated carbon that shares the same base benefits, but also has the ability to promote chemical reactions which are used to further remove chlorine and chloramines from tap water.

Benefits and Drawbacks of Carbon Filters

Carbon filters are extremely effective at removing chlorine which will help improve the taste and safety of your tap water. These filters are also passive, meaning you won’t waste water or electricity as water passes through them. Another reason consumers are drawn to them is that they require very little maintenance, usually only needing a quick and easy filter swap every couple of months.

reverse osmosis vs. carbon filters

Both reverse osmosis and carbon filters have advantages and disadvantages you should consider when choosing a filter for your home. Carbon filters are great for removing chlorine which improves safety and taste, but a single stage carbon filter isn’t enough to sufficiently remove all the contaminants that may be present in tap water. Reverse osmosis filters on the other hand, will remove far more contaminants but you’ll lose healthy minerals unless the system you use features remineralization technology to add these back in.

Aquasana’s OptimH2O® Reverse Osmosis + Claryum® Filter utilizes reverse osmosis in conjunction with activated and catalytic carbon filters along with ion exchange to remove 88 contaminants from your water while retaining healthy minerals such as calcium, potassium, and magnesium.

whatever you choose, make sure it’s certified

Regardless of whether you choose a reverse osmosis or carbon filter for your home, it’s important to make sure the filter you purchase is certified by a trusted third-party to remove contaminants. That’s where NSF Certification comes in.

As we’ve previously written, NSF is a third-party, nonprofit organization that develops standards for and certifies goods including clean water, food and consumer products. Their goal is to help consumers identify which products are up to their standards, and which ones aren’t.

Before buying any water filter, find one that passes NSF/ANSI standards (including NSF #42 for aesthetic effects and NSF #53 for health effects).

NSF Standard 42 – Establishes a minimum requirement for water filtration systems to remove a total of three contaminants such as chlorine taste and odor, as well as particulates that may be present in drinking water.

NSF Standard 53 – Establishes a minimum requirement for water filtration systems to remove a total of 57 contaminants, including lead, mercury, cryptosporidium, giardia, volatile organic chemicals (VOCs), and other harmful contaminants from drinking water.

  • Note: This certification does not mean that all these contaminants are tested – manufacturers can choose any of them to test to get this certification, so be sure your shopping list includes filters that sift out lead, mercury, and any other elements for the healthiest drinking water.

Aquasana has a wide range of whole house, under sink, and countertop water filters that use carbon filtration and are NSF certified to remove up to 99% of lead, asbestos, chlorine, chloramines, and other harmful contaminants that may be in tap water. We were the first on the market with an NSF Certification for systems designed to remove PFOA/PFOS so you can drink up, knowing your water is clean, healthy, and safe for the whole family.

If you determine an RO filter is a better fit for your needs, our Aquasana OptimH2O® Reverse Osmosis + Claryum® Filter is well renowned for its ability to effectively remove contaminants without sacrificing the healthy minerals your body needs. Check out our RO filter page to learn how it can instantly transform your tap water into the best drinking water available.