Reverse Osmosis vs Carbon Filter Systems: Which is Best?

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There are tons of drinking water filters available today, and two of the most popular offerings are reverse osmosis filters and carbon filters.

What are the key differences between these filter types, and which is best? We’ve shared all the essential information in this guide.

📌 Key Takeaways:

  • Reverse osmosis filtration is a multi-stage system that uses membrane separation to remove up to 99.99% of all total dissolved solids in water.
  • Carbon filters use adsorption to remove contaminants that affect taste and odor, but they don’t remove all dissolved solids.
  • RO water is much purer and cleaner than carbon filtered water.

🤔 What Are Reverse Osmosis Systems?

Reverse osmosis systems typically consist of four filter stages: sediment filtration, carbon filtration, semi-permeable membrane filtration, and post-carbon filtration.

Reverse osmosis systems force water through a membrane with tiny pores, which rejects most tap water contaminants.

Some reverse osmosis systems use a final remineralization filter to add healthy minerals back into the filtered water supply.

Tank-based ro system

🧐 What Are Carbon Filters?

Carbon filters are porous filters made from natural, raw organic materials, like charcoal, bone char, and coconut shells.

These filters can be used in systems driven by water pressure or gravity. They’re designed to target specific contaminants affecting the taste and odor of municipal tap water – mainly chlorine.

Types of carbon filter cartridges

📊 Differences Between Reverse Osmosis Systems And Carbon Filters

Let’s look in more detail at the differences between reverse osmosis and carbon filtration across several categories.

Filter Stages & Process

Carbon Filtration

Carbon filtration provides the intended results with just a single carbon water filter cartridge (although some carbon-based systems may combine several types of filters for more thorough filtration). The two common types of activated carbon filters are carbon block and granular activated carbon (GAC) water filters.

The activated carbon filtration process is called adsorption. Carbon filter cartridges have large surface areas and are extremely porous, which allow the filter media to grab onto as many contaminants as possible as drinking water passes through the pores.

Reverse Osmosis Filtration

Reverse osmosis units typically have four filtration stages:

  1. Sediment pre-filtration
  2. Activated carbon filter
  3. Semipermeable membrane
  4. Post-carbon block filter

In RO drinking water filtration systems, water is forced quickly through these filter stages in order. The sediment filter removes sediment; the carbon filter removes contaminants affecting taste and odor; the semipermeable membrane removes up to 99.9% of TDS, and the post-carbon filter polishes water and removes lingering contaminants.

Membrane filtration process

Related Article: Why is Starbucks water so good?

Contaminants Removed

Carbon Filtration

Carbon filtration removes only a few specific contaminants: organic chemicals, and poor tastes (namely chlorine taste) and odors.

Some types of activated carbon filters can also remove some volatile organic compounds (VOCs), some pesticides and herbicides, disinfection byproducts, heavy metals, and chloramines.

Reverse osmosis Filtration

By offering numerous filtration methods within one system, reverse osmosis units provide incredibly thorough filtration.

Reverse osmosis removes almost all contaminants, including dissolved salts and minerals, heavy metals, harmful chemicals, volatile organic compounds, and other organic and inorganic materials. An RO filter will also remove beneficial minerals. Only water molecules can get through the semi-permeable membrane, and the majority of harmful particles are flushed down the drain.

Water Purity

Carbon Filtration

Carbon filters don’t purify water. They simply remove a selection of common tap water contaminants with the primary purpose of improving the water’s taste and odor. The water from a simple carbon filter is filtered, but not purified.

Carbon beside a glass of water

Reverse Osmosis Filtration

Reverse osmosis in many cases can purify water. RO systems remove virtually all TDS, from toxic metals to chemicals, as well as fluoride, arsenic, and other common contaminants, resulting in clean, fresh water.


Carbon Filtration

Carbon filters are commonly available and relatively cheap to make from natural materials, so they’re a good budget-friendly filtration method. You can buy a water filter pitcher containing a carbon filter for as little as $25. Single-stage under-sink carbon filtration systems cost around $50-$70.

Reverse Osmosis Filtration

Because a reverse osmosis system comprises numerous filter stages and provides such a pure end result, this type of filtration is one of the most expensive methods available today. The average cost of an under-sink RO system is $300+, and whole-home reverse osmosis filters cost in the thousands.

Use Point

Carbon Filtration

Carbon filters can be installed in almost every type of water filter application, including countertop filters, gravity water pitchers and dispensers, under-sink systems, faucet filters, and whole-home filters.

Activated carbon filter cartridges

Reverse Osmosis Filtration

Reverse osmosis filtration systems are bigger and have more filter stages, which means they’re limited to three use points: under-sink, countertop, and whole-home. Under-sink RO systems are the most popular.

Installation & Maintenance

Carbon Filtration

Installing a carbon filter is easy to moderately challenging, depending on the filter’s use point. Gravity and countertop carbon filters require no setup whatsoever, while under-sink carbon systems usually have a simple installation process.

It’s easy to properly maintain a carbon filter – just replace the filter when the carbon’s surface is clogged and no longer capable of removing chlorine effectively. Carbon water filtration cartridges last 2-9 months on average, depending on the cartridge size and chlorine levels.

Reverse Osmosis Filtration

RO water filtration systems are more challenging to install because they combine numerous filter stages, a drain line, and – for conventional tank-based systems – a water storage tank. More room is required at the installation location, and more work is needed to install the system. Point of use filters are easier to install than point of entry systems.

Maintaining an RO system is a bigger job than maintaining a carbon filter because there are multiple filters to change, including the pre-filter, post-filter, and RO membrane. There are also more parts in the system that may become worn or clogged over time. The filters in an RO unit last 6-12 months on average, and the RO membrane lasts 24 months .

Installing an apec ro system


Carbon Filtration

Carbon filters are more efficient than reverse osmosis filters for a simple reason: they don’t waste water.

Water simply flows through one end of the filter and out of the other. Organic chemicals, bad tastes and odors are trapped in the filter media, while water particles pass through the filter pores.

Reverse Osmosis Filtration

An RO drinking water system wastes a small amount of water while it’s in operation. The wasted water carries rejected contaminants out of the RO chamber as the RO filtration process takes place.

Traditionally, RO systems would waste up to 4 gallons of water for every 1 gallon of water produced. Now, there are efficient systems that only waste 1 gallon of water for every 1 or 2 gallons of filtered water produced. Still, these systems are less efficient than carbon filtration, which wastes no water whatsoever.

Biggest Setbacks

Carbon Filtration

The biggest setback of most carbon filters is that they’re only capable of filtering, not purifying, water. Carbon filtration removes chlorine and a few contaminants that affect water’s taste and smell. That’s just how carbon filters work – they can’t filter water more thoroughly unless they’re combined with other filtration processes.

Aquatru filters 4 stages

Reverse Osmosis Filtration

The biggest setback of RO filters is that they remove healthy minerals from water. These minerals contribute to tap water’s pleasant alkaline taste, so removing them can make water taste less appealing. However, many RO water systems now come with optional remineralization filters that add healthy inorganic minerals back into the water after the RO process.

🆚 Which Is Best: Reverse Osmosis Or Carbon Filtration?

There are pros and cons of both carbon water filters and reverse osmosis filtration systems. Water filtered by carbon filtration isn’t as pure as water produced by RO, which removes many more contaminants.

However, a reverse osmosis system is bulkier, more expensive, and in many ways more limited than a carbon-based alternative. Carbon filter cartridges can be used in affordable filtration systems like pitcher filters, and they’re ideal for people who just want to remove chlorine and improve their water’s taste without spending a fortune.

In short, reverse osmosis is the best filtration method, but that doesn’t mean it’s your best suited choice of the two technologies.

  • Brian Campbell
    President & CEO, CWS, CWR

    Brian Campbell, a WQA Certified Water Specialist (CWS) and Certified Water Treatment Representative (CWR) with 5+ years of experience, helps homeowners navigate the world of water treatment. After honing his skills at Hach Company, he founded his business to empower homeowners with the knowledge and tools to achieve safe, healthy water. Brian's tested countless devices, from simple pitchers to complex systems, helping his readers find the perfect fit for their unique needs.

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