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Proper reverse osmosis systems remove almost all contaminants from water, usually at the point of use. The result: Highly pure, healthy, and refreshing drinking water.
Above that, RO systems provide enough filtered water for a whole family. Plus, they’re relatively easy to install and maintain, and cost-effective.
The only problem: How to find a unit that fits your needs? Don’t worry, here’s our collection of the best reverse osmosis systems in 2021.
On This Page You Will…
Best Reverse Osmosis Water Filtration System: AquaTru
Filter Stages: 4
Filtered Water: 1 Gallon of Purified Water in 10-15 Minutes
NSF Standards: 42, 53, 58, 401, P473
Annual Cost: ~$100-120
#1 Tankless RO System: Waterdrop WD-G3-W
Filter Stages: 3
Filtered Water: 0.28 Gallon Per Minute
NSF Standards: 58
Annual Cost: ~$115
#1 Under Sink RO System: Aquasana OptimH2O
Filter Stages: 4
Filtered Water: ~32 Gallons Per Day
NSF Standards: 42, 53, 58, 401, P473
Annual Cost: $180-220
Best for Well Water: Crystal Quest 1000C
Filter Stages: 12
Filtered Water: Up to 50 Gallons of Water Per Day
NSF Standards: –
Annual Cost: $100-155
In our opinion, the best reverse osmosis system in 2021 is the AquaTru. It’s tested and certified according to official NSF standards to remove up to 99.99% of more than 80 water contaminants. In other words, the purified water that comes out of an AquaTru is healthy and safe, and it tastes great!
But this is not even the main reason why we think the AquaTru RO system is the best of its kind. What we love about it is the plug & play functionality. Yep, this countertop unit is completely installation-free – no plumbing, no drilling. This is not only ideal for renters, it also saves you a lot of money if you’re not the kind of person that likes DIY projects. By the way, system maintenance is super simple and low-cost, too. 4.5 stars!
AquaTru RO Filtration System
|Purified Water:||1 Gallon in 10-15 Minutes|
|System Certifications:||NSF 42, 53, 58, 401, P473|
Delicious water, sleek design, straightforward under-sink install, and effortless filter changes – the Waterdrop WD-G3-W is our #1 tankless reverse osmosis filtration system in 2021. No tank means the unit filters water on demand rather than storing it in a tank which saves quite a bit of space under your kitchen sink. Taking into account the slightly higher price tag, it’s worth 4 stars from us.
Waterdrop WD-G3-W Tankless Under Sink RO System
|Reverse Osmosis Filter Stages:||3|
|Purified Water:||0.28 Gallon Per Minute|
|System Certifications:||NSF 58|
Our favorite under sink reverse osmosis system in 2021 is the Aquasana OptimH2O. Just like the AquaTru, it’s NSF certified to filter more than 80 harmful contaminants such as chlorine/chloramine (97.66%), mercury (>95.8%), lead (99.3%), VOCs (~99.4%), pentavalent arsenic (97.6%), chromium-6 (97.0%), fluoride (95.7%), overall TDS (95%), BPA (98.9%) and other chemicals, and PFOA & PFOS (96%).
Apart from effective contaminant removal which makes the water safe to drink, the Aquasana OptimH2O RO system also releases healthy calcium, potassium, and magnesium for improved taste and alkalinity.
Did we mention the affordable price and Aquasana’s reliable customer service? Bottom line: 4.5 stars!
Aquasana OptimH2O Under Sink Reverse Osmosis Water Filtration System
|Reverse Osmosis Filter Stages:||4|
|Pure Water:||32 Gallons Per Day (GPD)|
|System Certifications:||NSF 42, 53, 58, 401, P473|
The Crystal Quest 1000C respectively the 1000CP is best for well water. The only difference is that the latter comes with a pump in case your water is high in TDS or you don’t have enough water pressure from the well (65 psi is the optimum).
Why these water systems? Because they use more than 10 filtration steps to remove all contaminants commonly found in wells and more: Sediment, pesticides, industrial solvents, microorganisms, colloids, volatile organic compounds, PCBs, tastes, odors, metals especially iron, hardness, hydrogen sulfide (rotten egg smell), etc.
And if you want you can add a UV light water treatment stage on top for 99.99% reduction of bacteria, viruses, and protozoa. This turns the Crystal Quest 1000C into the 3000C, and the 1000CP into the 3000CP.
Please note: According to Crystal Quest, the above reverse osmosis water filtration systems can handle very hard water with up to 15 gpg hardness. Iron content shouldn’t exceed 2 ppm. This will result in a filtration capacity decrease of no more than 5%. At higher iron/hardness levels, the filters and membranes will clog prematurely. Tip: Contact Crystal Quest live support to discuss custom pretreatment.
Crystal Quest Under Sink RO Filtration System – Model 1000C
|RO Filter Stages:||12|
|Pure Water:||Up to 50 Gallons Per Day|
The Crystal Quest Thunder is our number one portable reverse osmosis system this year. That’s because it can be attached to any standard faucet in a matter of seconds – at home, in your RV, or while you’re on the move. This plus the compact design make it the ideal travel companion.
Customer satisfaction is high and the price tag is reasonable. Our only issue is that we’re missing NSF testing/certifications with specific contaminant reduction rates. 4.5 stars!
Crystal Quest Thunder Reverse Osmosis Water Filter
|RO Filter Stages:||10|
|Pure Water:||~50 Gallons Per Day (GPD)|
The NU Aqua Platinum Series 5-stage reverse osmosis system is perfect for people on a tight budget. It comes at a fraction of the cost of what you pay for the units of some of the leading brands. And not only that, you also get free shipping, a TDS meter, a 180-day satisfaction guarantee (refund or credit of original purchase amount if RO water doesn’t meet your expectations), and a full 5-year warranty. On top of that, replacement filters for one year cost as little as $50 which is unheard of.
How can the Nu Aqua RO system be so cheap? According to the company, that’s because Nu Aqua is the manufacturer of their own products. There’re no middle men so they can offer the best possible prices. We like! 3.5 stars.
NU Aqua Platinum Series 100-Gallon-Per-Day 5-Stage Reverse Osmosis System
|RO Filter Stages:||5|
|Pure Water:||100 GPD (Theoretical)|
In the last of our reverse osmosis system reviews: The HydroPerfection, or TMHP, which combines the best of all Home Master filters – an ultra-safe reverse osmosis filtration process including UV light treatment suited for both well water and city water, remineralization, and a built-in permeate pump to increase total daily water production while reducing waste water.
The result is an unlimited amount of highly purified and great-tasting alkaline drinking water. You just need to be willing to pay a premium. 4.5 stars!
Make sure to use our coupon code BOSFREERO at checkout and get FREE SHIPPING!
Home Master HydroPerfection (TMHP) Reverse Osmosis Filtering System
|RO Filter Stages:||9|
|Pure Water:||75 Gallons Per Day (GPD)|
How do the best reverse osmosis systems compare to each other?
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|RO Systems||Price||Filters||Additional Info|
|AquaTru RO System||$$$||4-Stage Reverse Osmosis Water Purification System, Separate Water Storage Tank||Reverse Osmosis Water System Filters Most Contaminants (According to Company Testing Results), Requires Electricity, Easy to Install & Maintain, Carbon Filtration|
|Waterdrop WD-G3-W RO System without Tank||$$$||3-Stage Reverse Osmosis Water System, No Water Tank, Dedicated Faucet||Tankless Design, Makes Use of Double Carbon Blocks, Booster Pump Included to Increase Amount of Water that Can Be Produced + Filtered Water Efficiency (Less Water Waste), Easy Installation + Maintenance|
|Aquasana OptimH2O Under Sink RO System||$$||4-Stage Reverse Osmosis Water Filter, Separate Water Tank, Dedicated Faucet||Lower Water Pressure, Filters Most Contaminants (According to Manufacturer Testing Data), Makes Use of Catalytic Carbon, Remineralization Stage Adds Healthy Minerals Back to Clean Water (Raises pH), Regular Under Sink Install|
|Crystal Quest 1000C & 1000CP RO Systems for Well Water||$$||5 (12) Water Filters, Separate Water Storage Tank, Dedicated Faucet||Filters Hydrogen Sulfide, Regular Under Sink Installation, UV Filter|
|Crystal Quest Thunder Portable Reverse Osmosis Filtering System||$$||5 (10) Filters Process, No Tank, Dedicated Faucet||Compact Design, RO Filter is Easy to Install (System Includes Everyting You Need)|
|NU Aqua Platinum Series 5-Stage Reverse Osmosis System||$||5 Water Filters, Separate Water Tank, Dedicated Faucet||Cheap, Easy Installation Process (System Includes Everyting You Need)|
|Home Master TMHP HydroPerfection 9-Stage RO System||$$$||9 Filter Stages, Separate Water Tank, Dedicated Faucet||75 Gallons Per Day TFC RO Membrane, Uses 5-Micron Sediment Filter + Catalytic Carbon Filter, Home Master Remineralization Stage Adds Beneficial Minerals Back to Clean Water (Raises pH), UV Light Kills Bacteria and Viruses + Other Types of Microorganisms, Permeate Pump Included to Boost Amount of Water that System Can Produce + Pure Water Efficiency (Less Water Waste), Straightforward Installation + Maintenance|
What do you need to consider when searching for your ideal RO system?
They may be more important with other water filtering solutions, but with RO systems, too, one should choose a unit that’s NSF certified (or tested) if possible. NSF certifications not only ensure a reverse osmosis system’s performance (as claimed by the manufacturer), but also that it’s made from high-quality materials.
Some reverse osmosis systems are also certified by the FDA which we consider less important.
Generally, top-notch RO systems feature at least 4 to 5 stages of filtration water has to pass through before it comes out of the dispenser:
Some pricier reverse osmosis systems come with additional components, for example to remineralize the water and balance pH by adding bits of calcium and magnesium.
There are 3 types of RO systems: Countertop reverse osmosis water filters, undersink reverse osmosis filtration systems, and whole house RO filters. You’re probably looking for option 1 or 2. A whole house RO system is usually hard to find in residential homes.
Personally, we prefer countertop-style systems because they’re installation-free and thus portable. That said, installing a standard RO system under the kitchen sink is not that big of a deal either (more info below). Performance-wise, there’s no difference between the best products from either categories.
A product must be able to meet your water demand. This means you want a large enough storage tank or, if there is no storage tank, a high enough flow rate.
Countertop RO systems are either autarchic or they connect to any standard kitchen faucet in under 5 minutes. It doesn’t get any easier than that.
In contrast, even well-designed under counter RO systems require proper installation which includes a few intrusive changes. Most importantly, you need to drill a hole in your kitchen countertop or sink (unless there’s a spare one) to accommodate the RO faucet. And you have to establish a drain connection which involves drilling in the sink’s drain line.
As for filter/membrane replacements, RO water systems featuring a modular design are the preferred choice here. Whenever you replace one of the filter elements you dispose the entire housing. This prevents bacteria and other germs from accumulating, plus the whole process doesn’t take more than a few minutes. No need to turn off the water supply, no spilling, no worries. The only drawback: Modular filters can be more costly than those with separate housings.
All RO systems waste water. That’s just how the reverse osmosis process works. However, the issue becomes worse if you’re homes feed water pressure is below the optimum. Fortunately, there’re electric pressure pumps to improve the pure water:waste water ratio significantly. Some RO systems already have them built-in, like the AquaTru, others can be upgraded. Another example is the Home Master TMHP; it uses a permeate pump.
We get it, people’s budget is rarely unlimited. Still, don’t make the mistake and buy an RO filtration system that’s low-quality. Those things can be a source of trouble – think leaking. Furthermore, cheap materials might leach new contaminants into your water that weren’t there in the first place.
You should also pay attention to cost and availability of replacement filters and RO membranes.
In our opinion, the best place to buy a reverse osmosis system is online. You not only have the largest product selection possible, you also get the best prices. Above that, with point-of-use RO systems there’s usually no need to consult a local water expert.
More on Reverse Osmosis Systems
Reverse osmosis is one of the safest water filtration methods which many U.S bottlers rely on. But what exactly is reverse osmosis and how does it work?
We like to explain reverse osmosis by first explaining the natural osmosis process:
In chemistry class, you may have learned that if two salt solutions are separated by a semipermeable membrane the solvent always moves from the low to the high concentrated side due to what’s called “osmotic pressure”. The process continues until both salt concentrations on either side of the membrane are equal.
In reverse osmosis the exact opposite happens. External hydraulic pressure (your home’s feed water pressure) is used to overcome the osmotic pressure and the flow of the solvent, usually water, is reversed. Now the water molecules move from the high concentrate solution (feed water) to the low concentrate solution (drinking water). The aim is to separate the water molecules from the dissolved impurities resulting in purified water.
Bottom line: Reverse osmosis is a great method to produce high quality water with almost no impurities left.
Based on the previous section you might be thinking a reverse osmosis water filtration system is composed of an RO membrane, a water storage tank, a faucet, and some tubing. In reality, it’s a bit more complicated…
We don’t know of any reverse osmosis water filter that doesn’t feature at least one pre-filter stage. Pre-filters are used to protect the delicate RO membrane from fouling. Usually, they’re sediment or carbon filters or a combination of the two.
As the name suggests, a sediment filter removes sediments from water; sand, silt, and other large particles.
Carbon filters contain either granular carbon or a carbon filter block. We can also differentiate between activated carbon and catalytic carbon. The latter is more effective at removing a broader range of harmful contaminants such as chloramine. Generally speaking, carbon is good for adsorbing disinfectants and their byproducts, organic contaminants, and various chemicals.
At stage 2 or 3, the semipermeable membrane comes into play. It more or less rejects all remaining water contaminants including heavy metals, salts, fluoride, radiation, BPA, and microorganisms.
The purified water leaves the membrane to continue its journey through the RO system. A second water stream that carries the concentrated contaminants is flushed down the drain.
Following the semi-permeable membrane come one or more post-filters. This is usually another granular activated carbon filter which removes any residual taste and odor.
Most reverse osmosis systems feature a water storage tank because they’re too slow to produce water on demand. The tank contains a pressurized water bladder to ensure fast flow when you open the water dispenser.
As the water storage tank fills it exerts increasing backpressure. Once the backpressure reaches about two-third of the incoming water pressure a piston in the so-called automatic shut-off valve (ASO) closes, preventing more water from entering the RO system. Only when water is dispensed by opening the RO faucet causing the storage tank backpressure to drop does the automatic shut-off valve re-open to allow new water to flow into the unit.
There are two types of faucets: Standard and air-gap faucets. An air-gap faucet features and air gap which acts as a siphon break to prevent drain water from flowing backward into the RO unit causing damage. Also, if the drain line is stopped up, the drain water can leave through the air gap.
Reverse osmosis systems that come with a regular non air-gap faucet usually feature one or more check valves to guard against drain backflow.
Air-gap faucet or regular faucet, which should you choose? Personally, we wouldn’t pay too much attention to this.
A check valve is a one-way valve. It allows reject water to flow to the drain but prevents it from flowing backwards toward the RO membrane in case of a blocked drain pipe.
A flow restrictor creates pressure in the semi-permeable membrane to control the flow ratio of pure water to reject water. In other words, it controls how much water flows down the drain and must be matched to the capacity of the RO membrane.
RO water lacks minerals and thus tends to be slightly acidic. You can counter this by adding an alkaline remineralization filter. It balances water pH and the healthy minerals will add to your daily nutritional intake.
An optional UV light stage is great if you’re dealing with microorganisms. The UV light will render them harmless.
A non-electric permeate pump improves the pure water:waste water ratio so that less water waste goes down the drain.
Electric pressure pumps also lower the amount of water waste while boosting overall water production.
As mentioned before, no matter how well-designed and efficient a system is, based on the nature of the reverse osmosis process it will always produce some wastewater. The waste water contains all the impurities rejected by the RO membrane and is usually flushed directly down the drain. In rare cases, usually with whole house RO system setups, the reject water is fed back into the water supply for recycling.
The ratio of pure drinking water to wastewater is a function of RO membrane pore size, solute concentration, feed water temperature, and feed water pressure. Larger pores, lower solute concentration, and higher water temp and pressure result in higher system efficiency.
However, you cannot or shouldn’t mess with the first three parameters. But what you very well can do is use a pump to increase low water pressure. 60 psi are considered ideal for most point-of-use RO filters. Anything below 30 psi is generally considered insufficient.
How much water does a standard reverse osmosis water filtration system waste? Around 3 to 5 gallons for every gallon of pure water. In comparison, reverse osmosis systems with an electric pump like the AquaTru waste no more than 0.25 per 1 gallon filtered. RO filters featuring a non-electric permeate pump can achieve a 1:1 water ratio at least.
Listing every single water contaminant that an RO system can possibly remove would take far too long. Instead, we decided to provide you with a list of contaminant groups:
TDS stands for Total dissolved solids and measures the combined total of dissolved organic and inorganic substances in a water source. The unit for TDS concentration is parts per million (ppm) and can be determined with the help of a TDS meter.
Is a reverse osmosis system worth it? That’s a good question. In our opinion it is if you’re dealing with contamination that regular filtration alone cannot solve. What we mean by that is more stubborn contaminants such as chromium 6 or arsenic – both very harmful when consumed – that can only be removed by ion exchange or, well, reverse osmosis.
Apart from the health aspect, an RO system will also greatly improve the taste and smell of your drinking water (although some people describe the taste as “rather flat”).
Another pro is ease of installation and maintenance, especially with countertop reverse osmosis filters. Speaking of maintenance, although usually a tad more expensive to purchase when compared to regular water filters, most reverse osmosis filter systems are pretty cost-effective in the long run. And filtering your own tap water is certainly much, much cheaper than buying bottled water.
A last benefit that comes to mind is clear ice cubes. Yep, RO water is so pure that even when frozen it’s crystal clear.
As far as disadvantages are concerned, we have the fact that, over time, reverse osmosis produces gallons of wastewater; the pure water is free from all impurities including healthy minerals; and the systems are relatively pricey at purchase.
Drinking water treatment by means of reverse osmosis filtration removes almost all impurities which is great. Only distillation can compete with the technology in terms of achieved water purity. But there’s one downside: An RO filter system cannot differentiate between healthy and harmful substances. As a result, it also removes essential minerals from water which in turn affects pH.
Let’s take calcium as an example: About 20% of our recommended daily intake (RDI) comes from the water we drink. The remaining 80% comes from our food. So if we drink RO purified water instead of bottled water chances are that we may not cover our calcium RDI entirely. The same applies to magnesium. For all other minerals, including iodine, iron and zinc, drinking water provides less than 5% of the RDI.
Water that has been deprived of its mineral content also tends to be slightly acidic which, according to our research, shouldn’t pose a problem. It might be more corrosive but that doesn’t make a difference when stored in an RO tank or consumed directly.
You’re concerned about using RO water for drinking and cooking and therefore not meeting your daily demand for essential minerals? The most convenient solution is to add a remineralization stage to your reverse osmosis filtration system. During the additional treatment step, beneficial minerals like calcium, magnesium, and potassium are released into the water. Access to high quality water – it doesn’t get any easier!
Another option is to use an electrolyte blend. The main focus here should be a balanced mineral composition. About 60 ppm calcium and 25 ppm of magnesium are ideal. An alternative to electrolyte blends are green powder blends and mineral-rich salts, e.g. Himalayan salt.
There’s only one way to answer this question: Identifying the type(s) of water contamination you’re dealing with. You can do this by checking your water quality report. If you’re on well water and don’t have access to an annual water quality report, you can send a direct sample to a professional test lab in your area or do the testing yourself.
Each option has its own pros and cons. A water quality report has to be provided for free but utilities are only required to test for certain contaminants and contamination that happens while the water travels from the utility to your home cannot be detected.
Hiring a professional lab such as this one can get really expensive if you want thorough testing.
And doing your own testing at best can only give you a very rough idea of what you’re facing.
Under-the-sink installation on the cold water line is the standard, obviously. If space is limited, consider your basement, garage, or a utility room and run a water line to the kitchen sink.
What you need to avoid is freezing temperatures. And always install a reverse osmosis water system downstream of any other water treatment equipment.
Do yourself a favor and gather all the necessary tools and supplies before you start with the actual installation:
Equipped with the right tools and detailed instructions, a reverse osmosis system DIY installation shouldn’t be too difficult to pull off for most people. Plus, you can find plenty of helpful tutorials on YouTube.
The following is a general description of the installation process. Please keep in mind that individual steps may vary from system to system and your specific plumbing setup.
First of all, drill a hole for the new water faucet. It should be positioned with convenience in mind.
Mark the spot with a center punch. Then drill the hole. Go extra slow when you are about to hit any metal. For a ⅜” or ½” hole, drill a smaller pilot hole first. Clean up any sharp edges before inserting the faucet stem through the hole and securing it from the bottom. Attach the quick-connect fitting.
For the drain saddle or adapter, you need to drill into your sink drain line. Go above and as far away as possible from the dishwasher discharge and garbage disposal, and at least 6″ above the p-trap.
Drill a ¼” hole in the top or the side of the drain line. Attach the drain clamps with screws. Be careful not to overtighten.
The feed valve connects your reverse osmosis system to the cold water line.
Start by closing the cold water supply. Open your regular kitchen faucet to release any pressure and remove the tubing from the cold water valve over a bucket. Install the new feed valve and close it for now. Connect the cold water tubing to the new valve and turn the water back on.
Place the water storage tank within 10 feet of the dispenser. Wrap enough Teflon tape around the threaded port at the top. Screw on the tank valve/connector.
You can mount the RO module if you want. When done, establish each connection using the color-coded tubing. Most reverse osmosis system feature quick-connect fittings. Simply push in the tubing as far as it goes. Pull back gently to check each connection.
Install the different filtration elements including the reverse osmosis membrane as instructed in the manual.
Almost done! Now it’s time to open the feed water valve and the dispenser to check for leaks.
It may take 10-15 minutes for the water to start dribbling out of the dispenser. Close the RO faucet and open the storage tank valve. Wait for the tank to fill completely. As soon as you can’t hear any more water running down the drain, drain the entire tank. Repeat the process and flush a second time.
Regular filter replacements are critical when it comes to reverse osmosis water system maintenance. Most filters require changing every six months, sometimes 12. A high-capacity RO membrane can be good for up to 3-5 years.
We also recommend annual system cleaning/sanitizing and making sure storage tank pressure is correct.
Sediment or carbon filter, both needs to be replaced sooner or later. How often? It depends on the filter itself as well as feed water condition and your water consumption. Our tip: Check the manufacturer recommendations.
How to replace? In a nutshell:
Most RO membranes last around 3 years. For a more scientific approach, you can test the remaining effectiveness of your membrane with the help of a TDS meter. How? Measure feed water and permeate water TDS. Then use this formula to calculate your current TDS rejection rate:
Rejection rate in % = (Total Dissolved Solids of untreated tap water – Total Dissolved Solids of pure water) / Total Dissolved Solids of untreated tap water x 100
If the rejection rate of your current membrane is below 80% it’s time for a new one.
Side note: In perfect condition, membranes remove up to 99 percent TDS.
Although not necessary in all cases, ideally you want to clean (and sanitize) your reverse osmosis water filtration system once a year.
Questions about reverse osmosis systems? Ask Away!
And keep in mind to revisit this buying guide from time to time as we are going to continue our hunt for the best reverse osmosis system and add new reverse osmosis system reviews occasionally.