Water Filter vs Reverse Osmosis: Difference + Which Is Better?
Written by: Alexandra Uta // Last Updated: Jun 26, 2023
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If you’ve been looking into water filters, it’s highly likely that you’ve come across information about reverse osmosis at some point.
You might be wondering what the difference between reverse osmosis and regular water filtration is. Also, which is the better option?
Learn everything you need to know below in our article about reverse osmosis vs filtration.
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Key Takeaways
- Traditional water filters use filter media for contaminant removal. Carbon, ion exchange resin, KDF, and other types of media trap, block, adsorb, absorb, or bind contaminants.
- Reverse osmosis forces water through a thin, semipermeable membrane at high pressure. Any impurities are rejected on the membrane surface and sent down the drain.
- While regular water filtration is limited in regards to the types of contaminant that can be removed, reverse osmosis removes pretty much everything.
- Reverse osmosis is one method of water filtration.
Water Filter vs Reverse Osmosis | Summary
Before we begin, it’s important to understand that reverse osmosis is technically one method for filtering water. So to those who are already familiar with water purification in general, it might not make much sense to compare reverse osmosis to water filtration. What’s usually meant by filtration in this case are traditional purification methods involving filter media like activated carbon.
The main difference is that traditional water filtration usually relies on having water pass through some type of filter media (activated carbon, ion exchange resin, KDF, etc.) which adsorbs, absorbs, binds, traps, or blocks contaminants.
Reverse osmosis, on the other hand, forces water through a specially crafted membrane which only allows water molecules to diffuse through. Pretty much all impurities are rejected on the membrane surface and flushed down the drain in a wastewater stream.
Both approaches have their advantages and disadvantages. It’s hard to say which one is better overall, especially when you consider the different types of contaminants addressed. In some cases, combining reverse osmosis with regular water filtration might make a lot of sense.
That being said, let’s get into the nitty gritty details.
What Is a Water Filter and How Does It Work?
A water filter is a relatively simple contraption designed to capture contaminants as water passes through it. Water filters come in many different versions designed to address different types of contaminants. It also isn’t rare to see different types of filters used alongside each other when a large number of contaminant types are to be targeted.
The most commonly used types of filter media include polypropylene, cotton, and other sediment filtering media; activated or catalytic carbon for removing organic chemicals, and ion exchange resin and KDF for removing dissolved ions such as heavy metals and salts.
Carbon Filters
Carbon filters, as the name implies, rely on carbon as their main filtration media. This carbon has been specially treated to make it as porous as possible – thus “activated” carbon. This allows it to adsorb contaminants into its surface pores as they pass through. It’s a simple idea, but a very effective one.
Carbon filters can effectively deal with a large number of different chemicals and organics that can be harmful to consume and also make water taste or smell unpleasant. That’s why they are the default option in many filtration systems. They are also often used as pre-filtration steps in reverse osmosis systems. More on that below.
Further Reading:
What Is Reverse Osmosis and How Does It Work?
Reverse osmosis relies on a thin, semipermeable membrane. The membrane’s pores are so fine that almost only water molecules can pass through them. Water is pushed through this membrane at a very high pressure. The water diffuses through but the contaminants accumulate on the membrane’s input side and are eventually flushed down the drain (the feed water stream is divided into 2: the filtered or permeate water and the waste or reject water). The latter is flushed down the drain containing all the contamination.
Reverse osmosis is highly effective, leaving behind nothing but pure, fresh water. It does have some disadvantages though:
- Most notably, reverse osmosis is sensitive to the presence of certain contaminants (sediments and chlorine), which can negatively impact its performance. Because of this, reverse osmosis systems usually rely on additional pre-filtration stages to purify water before it goes through the RO membrane element.
- Another minor drawback to reverse osmosis is that it removes some potentially beneficial elements along with all the contaminants. Water naturally contains various minerals (calcium for example) which are good for your health in reasonable concentrations. You might be used to obtaining those minerals from your daily water intake. If you switch to drinking reverse osmosis water, you might have to compensate in other ways. Don’t worry though, this is a trivial problem. It’s very easy to adjust your diet with the use of supplements. That way you will actually have more control over what you are eating on a daily basis because you will know the exact amounts of all of those minerals.
- And finally, and as mentioned before, reverse osmosis produces wastewater.
Difference Between Reverse Osmosis and Water Filtration
So, what’s the difference between reverse osmosis and filtration?
As you can see, the main idea is seemingly the same on both sides. Water is passed through a filtering device which captures contaminants and allows pure water to pass through. Or at least that’s how it looks on the surface. Once you start exploring both processes in detail, you will realize that they are actually quite different.
Filtering Process
With traditional filtration, water is forced to through the filter media using the pressure in your plumbing system or gravity. There are even filter straws that require sucking. The filter is designed to capture contaminants along the way, while still allowing water to flow mostly unobstructed.
On the other hand, with reverse osmosis, high pressure is necessary to force water through the membrane. Water temperature and salinity play a key role, but without adequate pressure reverse osmosis becomes highly inefficient.
Contaminant Removal
A reverse osmosis membrane removes rejects pretty much all types of contaminants on its surface, with some minor exceptions. It doesn’t do so well against dissolved gases and some pesticides, for example. But for pretty much everything else, it’s unmatched.
Regular water filtration is often not as thorough. Take activated carbon filtration: It’s great for removing chlorine, bad tastes and odors, sediments, and possibly VOCs, pesticides, disinfection byproducts, pharmaceuticals, and other organics. It might even reduce certain heavy metals, but that’s about it.
Flow Rates
In both cases, the flow rate of water is limited in some way. Reverse osmosis systems tend to be particularly slow in this regard. That’s why most setups usually incorporate a storage tank as a buffer. This is typically not necessary with traditional water filters, although it can still help in large households with multiple users.
Filter Life (Maintenance)
A reverse osmosis membrane can last a long time without being replaced. In some cases, you can go up to 5 years without swapping it out.
In comparison, traditional filtration systems require much more frequent maintenance. You shouldn’t dissipate replacing the filter every 3 to 6 (12) months. In some cases, like portable pitchers, you might even have to do it as frequently as every month or so.
Wastewater
One major drawback to reverse osmosis is that it may waste a lot of water. There are ways to mitigate this and reduce the amount of water that gets wasted, but in the end, you cannot make the process 100% efficient. Without any special measures in place, you can expect to waste as much as 3-5 gallons of water for every gallon you have filtered.
This is not the case with carbon filtration and similar filtration methods. No water is wasted or lost in the process.
Installation
Traditional filtration systems vary a lot in their installation complexity. Some are pretty straightforward, while others require a lot of work and might even involve calling a specialist.
Compared to that, most reverse osmosis systems require some additional effort to install. That’s because there are multiple filter stages, a storage tank, a separate water faucet, and a drain connection.
Cost
If you’re on a tight budget, you might want to go with a regular water filter. Pitchers are readily available at $20-30, more sophisticated ones come in at around $50-70. Countertop and under sink filters start at $50-100.
Reverse osmosis systems are usually more expensive. You’ll probably need to invest $200 at the least.
This doesn’t account for the long-term maintenance costs though. Sometimes buying a reverse osmosis system and maintaining it over time can be more economical than investing in a regular water filter.
Similarities
As mentioned before, there are some similarities in both traditional water filtration systems and ROs. In the end, they both rely on using some kind of barrier to prevent contaminants from making their way into your drinking water. However, the actual science behind the filtration process is very different on both sides.
These systems also look pretty similar visually in some cases. What you see from the outside is a sump that houses the filter cartridge, along with some tubing connections to hook it up to your plumbing.
Pros and Cons of Water Filters
- Pro: many different types of filter media that address specific types of contaminants
- Pro: lower price (for most models)
- Pro: easy to install in most cases
- Con: often only effective against specific contaminant types
- Con: requires more frequent filter replacements
Pros and Cons of RO
- Pro: very thorough filtration that effectively removes close to all contamination
- Pro: low overall maintenance requirements
- Pro: doesn’t use any chemicals, better for the environment
- Con: removes some healthy minerals
- Con: usually requires pre-filtration
- Con: wastes water
- Con: works slowly, requires a storage tank for optimal operation
- Con: requires significant water pressure
Water Filter vs Reverse Osmosis – Which Is Better for You?
With all that said, which of the two should you go for – water filter or reverse osmosis system?
As usually happens in the world of water filtration, the answer depends. You have to identify your specific requirements. Namely, the types of contaminants you’re dealing with and their concentrations. Then you have to have a good overview of your budget. These points will allow you to narrow down your search to a solution that covers all your bases.
Test Your Water Supply Quality
It’s important to have your water tested so that you know where you stand. You can generally do this in two ways.
- The easy one is to buy a test kit from your local hardware store. However, that is not a very precise method. Also, diy test kits are limited in regards to what contaminant types they can detect.
- A much better option, if you’re serious about your water filtration, is to have your water professionally tested at a laboratory. This costs more money and takes time, but it will provide you with a complete overview of what you’re dealing with. You will get a list of all contaminants present in your water and their exact concentrations.
- If you don’t like either of the two options, you can check your latest water quality report (provided you’re on a public water supply).
This will allow you to identify the exact type of filtration that fits your situation. Some of you will find that they are perfectly fine using a simple activated carbon filter. Others face heavy water contamination where reverse osmosis is often the only solution.
What Is It That You Want?
Another point to consider is how you intend to use your new water filter. What is truly important to you? Do you want to have constant access to fresh water on demand without having to wait? Do you care about improving the smell and taste of your water? Do you want the healthiest of waters you can get? And how much maintenance can you see yourself realistically putting into a system in the long term?
Being honest with yourself about these points will go a long way toward helping you identify a suitable solution. Sometimes you might realize that you don’t actually know what you want. That’s perfectly fine. In that case, talk to a water treatment expert. They will be able to guide you through your purchase and help you identify the points that actually matter to you.
If you have any questions about reverse osmosis vs filtration please don’t hesitate to leave a comment below!
About the Author Alexandra Uta
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