- 1 Introduction to Reverse Osmosis Filtration
- 2 Best Reverse Osmosis Water Filter System Reviews:
- 2.1 1. Home Master – (Model “TMHP HydroPerfection”) RO System
- 2.2 2. iSpring RO System – Model RCC7AK-UV (7 Filter Stages)
- 2.3 3. APEC Brand ROES-Ph75 RO Water Filtration System
- 2.4 4. Express Water Reverse Osmosis Filtration System: 10 and 11 Stage Models
- 2.5 5. Reverse Osmosis Revolution Countertop Portable Universal 5-stage Reverse Osmosis Water System
- 3 A Guide to Help Choose The Best Reverse Osmosis System
- 3.1 Reverse Osmosis Filtering Systems Explained:
- 3.2 Principles of Reverse Osmosis:
- 3.3 Reverse Osmosis Filters and how they work:
- 3.4 A Step-by-Step Explanation of Reverse Osmosis Filtration:
- 3.5 Some Reverse Osmosis FAQ:
- 4 What Contaminants are Removed by Reverse Osmosis Systems?
- 5 Sources Cited
Introduction to Reverse Osmosis Filtration
Reverse osmosis filtration systems are arguably one of the best and most popular options available to the homeowner as a method of providing your family with clean, fresh water. Known for their efficacy, their multi-stage filtration technology enables these systems to remove up to 99% of certain toxins and contaminants from the water (e.g. radionuclides, arsenic, uranium, radium, nitrate, etc) 1, and depending on the source, anywhere from 85% - 95% or more of other contaminants.2
On this page, we'll introduce you to the best reverse osmosis (RO) water filters and systems that we have found (updated for 2019). As with any system, there are different pros and cons which may affect your decision, depending on your primary concerns. We'll talk about what these systems can and cannot remove as well! For example, while RO can remove arsenic and fluoride, it cannot remove radon gas or hydrogen sulfide ("rotten egg" smell) on its own (both require filtration, and in the case of radon, aeration to keep it from getting into the air in your home).
Don't worry if you don't have a full understanding about reverse osmosis water filters yet. We'll explain things in a way that will clarify the different steps in this process so that as consider the best option for you and your family, it won't feel so overwhelming!
One of the things consumers seem to agree with over and over is that reverse osmosis filters are not difficult to install or maintain. Yes, you do need to switch out filters once in a while, but this is the case with nearly any type of unit.
As you begin reviewing the best reverse osmosis system option for your own needs, please remember that the best starting place is to ensure that what you are trying to get rid of in your water can be removed to begin with.
Since you probably want to have a look at some systems right away, let's jump in.
There's lots more reading about RO systems further on down this page below these initial previews!
Home Master HydroPerfection
Water Production: 75 GPM
Filtration: 5 Stages (Including UV)
Price Point: Approx $300
iSpring Under Sink 7-Stage
Water Production: 75 GPM
Filtration: 5 Stages (Including UV)
Price Point: Approx $300
APEC ESSENCE 6-Stage
Water Production: 75 GPM
Filtration: 6 Stages
Price Point: Between $200- $300
Express Alkaline UV 11-Stage
Water Production: 100 GPM
Filtration: 11 Stages (Including UV)
- For 10-Stage, Approx $200-$300
- For 11-Stage, Approx $300-$400
Reverse Osmosis Revolution Portable/Countertop
Water Production: Approx 3 Gallons per Hour
Filtration: 5 Stages
Price Point: Between $100-$200
A Guide to Help Choose The Best Reverse Osmosis System
Whether you are looking to install a portable or a built-in system, we know you’ll have questions. Some of the more common questions we get are not only “what are the BEST reverse osmosis systems,” but also: Which are the most efficient reverse osmosis systems? Which ones are best “under the sink” models? How about the “whole house” models?
And, now that you’ve seen a few top-rated RO systems and what some of them offer, you may begin to wonder if you need “just a little” bit of filtering, “a WHOLE LOT of filtering,” or if you need to use UV light or add minerals.
Reverse Osmosis Filtering Systems Explained:
In simple terms, a Reverse Osmosis System (aka RO), is a method designed to force water through a series of semipermeable membranes that have microscopic pores designed to keep the unwanted substances behind, allowing only the clean water through.
The way this is accomplished is that the pores in the membrane are so small, that the contaminants whose particles are larger than the water particles simply cannot pass through. Naturally, the result will be tastier and cleaner water on the “other side” of the RO membrane!
It isn’t just homeowners like us who love a Reverse Osmosis system. It is exceptional for treating water in a variety of industrial settings as well. More and more farmers are using it in their operations (it is also popular in hydroponic farming). In addition, breweries love it because it means a higher quality water for their beers – and higher quality water means a higher quality beer. The same goes for restaurants and coffee houses. It is used in desalinization plants. The military has even developed a portable RO system that can not only be used in the field, but also for disaster recovery, such as the Water Assessment and Purification Toolkit or WAsP. 3 The use for RO systems is endless.
Principles of Reverse Osmosis:
Let’s first look at the principle of osmosis to begin with. We experience osmosis every day since it is a totally natural process in our lives!
Most scientific explanations of osmosis refer to a “solvent” of a lesser concentration being moved through a semi-permeable membrane into a more concentrated solution. A “solvent” is something that can dissolve another substance; therefore, water is a solvent since it can dissolve another material.
For example, water can dissolve salt or sugar.
So, let’s use the example of salt water for our explanation. In osmosis, you have two solutions separated by the “semi-permeable” membrane: On one side is a less concentrated (less salty) liquid, and on the other side is a more concentrated (more salty) liquid.
In osmosis, what will happen is that the less concentrated (less salty) water naturally wants to move toward the more concentrated (more salty) water because it wants to create an equilibrium between the two sides.
Using another example: our own bodies! If you are dehydrated, your cells shrink from lack of water – and your cells would be the “more concentrated side” of the equation. When you drink water, the water is naturally delivered to your water-starved cells through the semi-permeable membrane of the cell until the equilibrium is achieved.
Now, you may ask, “But what if I don’t WANT the water to be salty?” THAT is where REVERSE Osmosis comes in. It takes the process we just illustrated and REVERSES it. So, in the case of the salty water example, instead of the less salty water migrating to the more salty water, we exert a force on the salty water and move it through the membrane to keep the salt particles BEHIND, resulting in clear water on the other side of the membrane.
Remember that in a real life situation, there are going to be different particles that we want to remove from our drinking water, and the system that you choose will have the filters and the semipermeable membranes designed for those purposes. So let’s have a look at these filters and how they work.
Reverse Osmosis Filters and how they work:
As we just illustrated, the general way in which reverse osmosis filters work is that the water containing the undesirable particles is forced through a semi-permeable membrane. As it does this:
- The reverse osmosis membrane’s pores (which are very, very small) blocks the vast majority of the particles (estimates are that anywhere from 95% – 99% of contaminates can be removed via RO)…
- These blocked particles are considered waste (wastewater) and are discarded and drained away (the technical term for this is “reject water” or “concentrate water”).
- This concentrate is “rinsed away” with more water. In some systems, this wastewater can be recycled; although for homeowner use, it is more likely to simply be discarded unless the consumer desires to use it for purposes where filtered water is not required.
You are probably wondering how much pressure is needed to move this water. It’s a good question, and the answer is, “it depends,” because water with less contaminants will not need as much pressure as water with higher levels of contaminants.
The technical name of the water that comes through “the other side” of the filters is “permeate” water in scientific and industrial terminology; however, as a homeowner, you can simply call it “filtered” (in some cases you may hear it referred to as “pure” water; however, it should be noted that NO filtration system will remove 100% of particles).
How the “Reject Water” Is Separated from “Permeate Water”
Unlike other filtration systems (where the filters themselves collect or absorb the undesirable particles), with reverse osmosis, one “outlet” is necessary to get rid of the “reject water,” and another “outlet” is necessary to carry the clean, filtered water to a tank or its point of use. This setup is called “cross filtration.”
Cross filtration also accomplishes another task; and that is to keep the semipermeable membrane clean so the contaminants that are left behind don’t clog up the membrane. Consumers still need to replace filters occasionally, but not nearly as much as they would be if the contaminants were left in the system.
A Step-by-Step Explanation of Reverse Osmosis Filtration:
While some RO systems have fewer stages than others (we’re seeing anywhere from 3 stages to 11 stages), we’ll outline the steps in one that uses more so that you can get an overview of a larger system. When you investigate the various options available to you, you’ll see the number of stages/steps each system offers right up front (e.g. “Home Master 6-Stage TM ULTRA-ERP Reverse Osmosis System,” “APEC ROES PH75 6 Stage Reverse Osmosis Water System,” or “iSpring RCC7AK-UV Deluxe Under Sink 7-Stage Reverse Osmosis Drinking Water Filtration System,” or the 11-Stage “Express Water Alkaline Ultraviolet Reverse Osmosis Filtration System.”)
You may not need an 11-Stage or even a 7-Stage system, depending on your reasons for purchasing an RO system. If you don’t have many contaminants in your water, you may be completely fine with a 3-Stage system! If you want to remove a number of compounds such as fluoride, lead, chlorine, arsenic, etc, you may opt for a system with multiple stages. No matter how many “stages” are in each system, they will share a few commonalities – especially when it comes to the reverse osmosis semi-permeable membrane itself.
Generally speaking, all reverse osmosis systems are going to have a “pre-filter” for sediment, followed by one or more pre-carbon filters, then the semipermeable reverse osmosis membrane filter (or filters), another, “post-carbon” filter, and in some cases, an alkaline remineralization option (since RO removes the minerals from water) and even a UV sterilizing option in some.
The General Steps/Stages of a Reverse Osmosis System:
- 1st Step/Stage: Pre-Filter (Sediment Filter) – In this stage, the feed water passes through a sediment filter designed to remove larger particles such as rust, dirt, or silt that may be in in the feed water. It’s important to remove these particles before they get to the RO membrane – there is no need to put these larger impurities through a reverse osmosis membrane when a simple sediment filter can take care of them immediately (and thereby saving unnecessary wear and tear on your membrane and the system overall).
- 2nd Step/Stage: Pre-Filter (Carbon Filters – can encompass several stages in this step) – There may be more than one carbon filter in this stage. In systems that include 2 carbon filters, for example, then this would be considered 2 separate stages. In systems that include 3 of these filters, each of these is a separate stage. As the water passes through the “pre-carbon” stage, chemical tastes and odors (such as chlorine) will be removed, as will a number of other organic contaminants, or VOCs (Volatile Organic Chemicals). In systems where there are more than 1 carbon pre-filter, you are likely to see both the Granulated Activated Carbon (GAC) and Carbon Block (CTO) filters.
- 3rd Step/Stage: Reverse Osmosis Membrane – This is where the RO magic happens! The water is now pushed, under pressure, through the semipermeable membrane, which blocks up to 95%-99% of the smallest particles in the water, allowing only fresh, clean water to filter through. THIS is where you’ll get rid of the fluoride, radionuclides, lead, etc.
- 4th Step/Stage: Post-Carbon/Additional Carbon Filtering (“polishing”) – Once the water has passed through the reverse osmosis membrane, it continues through another carbon filter (usually made from coconut shell) to ensure that any remaining odors and residual particulates are removed.
- 5th Step/Stage: Ultraviolet (UV) Light Treatment (Optional) – Used to ensure that any residual bacteria or other microorganisms that somehow makes it through the RO membrane is eradicated. Note that this stage is not used as frequently, and there are mixed opinions as to whether or not to include them. Some of the arguments against adding UV is that it takes electricity to run, the heat from the light can cause the components under the sink to weaken or otherwise become brittle, or the water may come out hot. While most consumers don’t opt for this particular stage, some do, and therefore a number of manufacturers offer systems that include a UV sterilization stage.
- 6th Step/Stage (up to even 11 Stage): Remineralization (also Optional) – At this point in the RO process, pretty much all the minerals have been removed from the water (approximately 95%), including those which some people DO want (e.g. calcium). Also, some people don’t particularly care for the taste of demineralized water, saying that it tastes “flat” or “bland” (also a common complaint about drinking distilled water). This is where the “remineralization” comes in. In some units, a filter does the trick to replace some of the calcium. You can see in numerous highly-rated and best-selling RO systems featured here on the site, this stage is added. For example, with the iSpring RCC7AK product, after water passes through the first 5 stages of the system, there is an additional stage called the “Alkaline Remineralization (AK) stage.” So, if mineral depletion is a concern, this additional stage can be helpful.
Do Reverse Osmosis Systems Require Electricity?
On their own, household RO water filtration systems do not require electricity since it is the pressure of the water itself that moves it through the system. However, if the system you are using includes a pressure booster pump, or a UV sterilization stage, then you will need electricity. If the water coming into your home doesn’t have enough pressure on its own, chances are you would need a pump (see next question). Reverse osmosis systems used for industrial purposes use pumps, and therefore, those would need electricity to run.
Will I need a pressure booster pump?
Because RO systems depend on pressure to work, if your household water pressure isn’t high enough, you will need a pump. According to iSpring, which manufactures some of the highest rated reverse osmosis water filtration systems on Amazon, if your pressure is less than 45 psi, the system cannot work. If your water comes in at 60 psi (which they say is fairly typical for most city water supplies), you should be fine. One of iSpring’s higher end units states that their system runs best at 80 psi, which is what their own pressure boost pump supplies.
Do I need a permeate pump?
You may not need to use a permeate pump if your system fills quickly enough to suit your needs. Some manufacturers say that a permeate pump can reduce the waste water by up to 80%, while increasing the efficiency of your RO system tank’s fill time by 65%. You do not need electricity to use a permeate pump since it runs on the pressure in the system. A lot of people DO opt to have a system that uses a pump since they would prefer a slightly more water-saving option. In some of the reviews of RO systems above, you can see that a few of them come with the pump. Check out this short video that shows how a common permeate pump is installed.
How Much Water Does Reverse Osmosis Waste? This is one of the most common questions with regard to RO systems, and understandably so since water that is used to wash the impurities from the RO membrane goes down the drain (unless it is collected and recycled). However, it is important to understand that the process of reverse osmosis USES water to “flush” away the debris and contaminants left behind so that these residuals don’t harm or plug up the membrane. Think of a toilet flushing waste away – and for the most part, we certainly don’t think of the toilet as “wasting” water. With reverse osmosis, the water that is used to wash away the residual impurities only runs when the system itself is in operation. So, once your system has filled the pressure tank, it stops running – and of course, so does the water.
There is another thing to consider when we think about “waste.” Did you know that numerous brands of bottled water are also produced by Reverse Osmosis? So, even you feel that you might just go back to bottled water, not only might you be purchasing filtered water produced via RO (which will also have used water to clean and clear the membranes at an industrial level), but you will be going right back to using plastic bottles (which is another problem altogether).
Should I go with a Whole-House Filter or a Point of Use Filter?
The answer to this depends on a number of factors. Is the water discoloring clothes? Does the water leave iron or other metallic residue in your tub/shower/sink? Does the water smell foul throughout the system? How much water does your household use? Also, consider the “waste water” factor – if you honestly don’t think you need an whole house filtration system, you will see less water waste using an under counter reverse osmosis water system. However, if your water supply affects your quality of life in every aspect of your day to day existence, you may want to consider treating your water at the point of entry to alleviate all concerns.
What do Point of Use Reverse Osmosis Systems include?
Most systems will come to you complete with all the filters and membranes, the tubing, pressurized storage tank (which will hold the filtered water – aka permeate), You will notice that with a lot of these under sink reverse osmosis water filters, there is an additional, dispensing faucet on the countertop. That is because when installing an RO system for cooking and drinking water, there is no need to put all your water – for example, water you’re going to use to wash dishes – through the system, so the smaller tap is installed to specifically deliver only the water filtered via reverse osmosis. The exception would be a countertop reverse osmosis system such as the one we featured above, which is a portable unit and therefore would not have a pressure tank to store the filtered water.
How much filtered water will my RO System produce each day?
Each system is different. In our comparison chart and reviews, we include the metric of “gallons per day” or “GPD” reported by each manufacturer. Some advertise 50 GPD while others state 75 GPD, 100 GPD, etc. Related to this question is “water flow” or output at the faucet, which will also depend on whether you are using a pressure tank or not. For example, if you are not using a pressure tank, the flow from the system to the tap will be slower than if the tap was being fed from the pressure tank.
How long will my filters last?
Reverse osmosis systems are quite simple to maintain. And each manufacturer will give you an estimate of when you should change the filters.
Of course it depends largely on each system as well. In our review of the Reverse Osmosis Revolution’s PORTABLE, countertop unit, they estimate that their filters will last about 500-700 gallons. This is considerably different from a more permanently installed system.
For example, take a look at this illustration from iSpring, which shows you about how long each of the filters in their iSpring RCC1UP-AK 7-Stage Maximum Performance 100 GPD system will last. No matter which system you use, it’s a given that you will be saving a lot of money over continued purchases of bottled water.
What Contaminants are Removed by Reverse Osmosis Systems?
This is one of the reasons why RO systems are so highly recommended by the CDC. Depending on the system, you can reasonably expect to see a 95% – 99.99% reduction in contaminants. Some systems claim that they remove up to 1,000 different substances. We have created this page that discusses the basics of what each main type of filtration option removes. We’ll go into a little more depth here.
As far as what the RO membrane itself is able to remove, it may be helpful to realize that the pores are so tiny that anything larger than 0.0001 microns is likely to be blocked! If you consider that an average human hair measures about 50 microns, you can understand why the reverse osmosis process is so effective!