Written by: Alexandra Uta // Last Updated: Jan 31, 2024
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Top Pick: What’s the Best Reverse Osmosis System?
The best reverse osmosis system in 2024 is the AquaTru, because it is NSF-certified to remove 80+ potentially harmful water contaminants, fast, installation-free, easy and affordable to maintain, water-saving, and it has a long filter life of up to 1,200 gallons.
With so many different reverse osmosis systems on the market – some are good, some are bad – it can be hard to find the best one for your needs.
That’s why we’ve spent hundreds of hours researching and reviewing more than 39 of the top reverse osmosis systems since our buying guide was first published on July 21, 2020. By evaluating, testing, comparing, and ranking the products, as well as updating and editing our guide, we hope to help you make the best buying decision.
In our opinion, the best reverse osmosis system in 2024 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!
Deal Includes Free Replacement Filter Set + 15% Discount Code
Alexa’s Video Review
Alexa, our inhouse video content producer, has ordered and tested the AquaTru Reverse Osmosis System. In other words, she set up the AquaTru with her own hands and used it in her home for several weeks to gain invaluable first-hand experience and insights. Alexa has documented the entire process and shares her opinion on the water filter in the video below:
The 3-part filtration system is quite impressive. It really removes everything out of the water. As far as water filtration systems go this will be a very high quality option for you. (…) Overall my review of this system is going to be a 4.5 out of 5.
Sara has also tested the AquaTru. And here review even includes lab testing, so a comparison of the unfiltered vs. filtered water:
The AquaTru Reverse Osmosis Countertop System has a very effective filtration process backed by NSF certifications, it has very little wastewater, it is an installation-free system and it is very easy to use, and the maintenance is pretty affordable.
AquaTru reverse osmosis water filtration system can be set up within a few minutes.
Space-saving design.
Very easy to use.
Clean water collects in removable front tank (great for cooling) and can be dispensed. Contaminants are captured in back tank ready to be discarded.
Uses combination of sediment filter and coconut shell activated carbon pre-filter to trap dust, rust, and other large particles, and adsorb bad tastes and odors as well as chlorine (96.6%) and a bunch of chemicals.
Reverse osmosis filter membrane removes heavy metals such as lead (99.1%) and chromium-6 (97.2%), fluoride (93.5%), cyst (99.99%), and TDS (87.1%).
Lastly, water passes through coconut shell activated carbon block post-filter. It reduces organics, PFOA and PFOS (97.5%), pesticides, pharmaceuticals, etc. Also filters any residual taste.
4-stage filtration process is NSF Standards 42, 53, 58, 401 and Protocol P473 certified.
Outstanding test results.
Guarantees pure drinking water and the safety of your health.
Booster pump included to force water through reverse osmosis membrane.
Fast filtration: The RO system purifies one gallon of water in 10-15 minutes.
Improves pure water:waste water ratio. Only 20% of the input water goes down the drain, compared to 3-5 gallons that standard reverse osmosis systems waste for every gallon of filtered water produced.
System maintenance doesn’t require much time or effort thanks to long-lasting filters that can be replaced with a simple twist.
AquaTru tracks time and the amount of water used to tell you when one or more of the filters require changing. You’re probably looking at annual/biannual replacements. Cost? Around $100-120 per year which is affordable compared to the competition.
All plastic is BPA and BPS-free.
Everything is covered by warranty for one year.
Cons
Potential leaking due to design flaw.
Some reviewers said their system malfunctioned after a couple of months use.
Our Rating
Filtration Performance: 4.5/5.0
Filter Life: 5.0/5.0
Price: 4.0/5.0
Annual Filter Replacement Cost: 5.0/5.0
Overall: 4.5/5.0
Best for
The AquaTru is best for people who want a reverse osmosis system that’s compact, installation-free, easy to use, very effective, and fast.
2. Best for Tankless Reverse Osmosis Water Filtration: Waterdrop G3
Delicious water, sleek design, straightforward under-sink install, and effortless filter changes – the Waterdrop G3 is our #1 tankless reverse osmosis filtration system in 2024. 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.
Get 5% Off on Top of Any Current Waterdrop Sale! Use Code: G3P600BOS
Sara’s Video Review
Being part of the BOS team, Sara has ordered and tested the Waterdrop G3 Reverse Osmosis System, which means she has installed the system with her own hands and used it for several weeks for some genuine first-hand experience! Sara has documented the entire process, including her findings and personal verdict, in the video provided below:
Right now the Waterdrop G3P600 is our #1 under sink RO system and also our favorite tankless model. That’s because it offers the complete package: Fast and effective water filtration with a solid pure-to-drain ratio, great usability, a quality build, and acceptable upfront and long-term cost.
3-layer composite filter (polypropylene cotton + coconut shell activated carbon block) removes chlorine, bad tastes and smell, and sediment like sand and rust.
RO filter membrane rejects harmful metals, bacteria, viruses, and much more.
Another activated carbon filter block gives the water a finishing touch improving aesthetics.
System is NSF Standard 58 certified for TDS rejection.
System comes with pump which increases pressure to push water flow rate to 0.42 gallon per minute. One cup fills in little more than 8 seconds so no long waiting times.
The pump also reduces waste water flowing down the drain from the standard 3-5 gallons for every gallon of filtered water to as little as 0.67 gallon.
All plastic is BPA-free to avoid recontamination.
The dispenser is metal for high durability.
Waterdrop reverse osmosis systems can be installed by non-professionals within one to two hours.
You shouldn’t have problems if you’re handy with tools and as long as you follow the instructions provided.
Smart faucet uses LED to indicate filter status. White light means your RO filters are working just fine. When you see yellow light you have less than 40 gallons of reverse osmosis drinking water left (about 15 days). Change filters immediately once you see red light and hear beeping sound when dispensing water.
Similar lights are found on system front panel.
You no longer need to remember date of next filter change.
TDS monitor on system front panel + faucet base also indicate filtration effectiveness which is another feature to oversee filter status.
Filter replacements can be done in 10 seconds with no need for tools and closing feed water line. Yearly cost: We estimate roughly $145.
Waterdrop G3 reverse osmosis water filtration system comes with a 30-day money-back guarantee that allows you to return the product for a full refund + manufacturer warranty (one year).
Cons
We have little doubt that the Waterdrop is effective but we would have preferred more NSF certifications.
You may need to drain up to a full gallon of water before the system achieves optimum TDS (TDS creep).
Our Rating
Filtration Performance: 4.0/5.0
Filter Life: 5.0/5.0
Price: 3.5/5.0
Annual Filter Replacement Cost: 4.5/5.0
Overall: 4.0/5.0
Best for
The Waterdrop G3 is best for people who want a tankless reverse osmosis system that’s compact, easy to use and service, effective, and fast.
3. Best for Under the Sink: Aquasana OptimH2O Reverse Osmosis System (with Remineralization!)
Our favorite tank-based under sink reverse osmosis system in 2024 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
Most people are more than happy with their purchase.
3-stage system removes 88+ contaminants from water.
Full system is certified according to NSF/ANSI standards 42, 53, 58, 401, and P473 for guaranteed performance.
Uses activated carbon filter to eliminate chlorine and larger particulates.
RO membrane filters out heavy metals, microorganisms, and many other potentially harmful contaminants.
Claryum (filter stage 3) combines activated with catalytic carbon and ion exchange resin to adsorb pesticides, herbicides, chloramine, a bunch of heavy metals, drug residues, etc.
Alkaline remineralization filter enriches water with healthy calcium, magnesium, and potassium to improve taste and balance pH.
3 full-metal water faucet designs to choose from: Chrome, brushed nickel, and oil-rubbed bronze.
RO system can be DIY-installed. All required parts + step-by-step installation instructions are included in the package.
Just make sure to follow every single step as disclosed in the manual. Contact customer service if you don’t know what to do next.
Aquasana OptimH2O reverse osmosis system is easy to maintain thanks to twist on/off filter housings and quick-connect fittings.
RO system is covered by 2-year limited warranty + 90-day satisfaction guarantee for peace of mind.
Cons
A few people had problems with leaking.
Aquasana sends replacement parts free of charge.
Issues with overall quality, especially water dispenser which feels flimsy.
Relatively low water flow rate.
Annual replacement filter cost: About $240 depending on water quality and usage.
More than what you pay with most of the competition.
Join the Water for Life filter program to get discount.
Our Rating
Filtration Performance: 5.0/5.0
Filter Life: 4.5/5.0
Price: 4.0/5.0
Annual Filter Replacement Cost: 4.0/5.0
Overall: 4.5/5.0
Best for
The Aquasana OptimH2O is best for people who want an under sink reverse osmosis system that’s easy to install and service, effective, and that provides remineralized drinking water.
4. System Best for Well Water Source: Crystal Quest 1000C or 1000CP (Optional UV Filter)
The Crystal Quest 1000C/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
Reverse osmosis under sink water filter systems use 12 stages of filtration.
Filter stage 1 is an activated carbon block (5-micron nominal). It adsorbs chlorine and all kinds of chemicals. Furthermore, it traps undissolved matter to protect the following filter stages from clogging.
Stage 2 is a 0.02-micron ultrafiltration membrane. Ultrafiltration is effective for the reduction of microorganisms and other organic and inorganic molecules.
At stage 4, the water passes through granular activated carbon (GAC). Say goodbye to 99.9% chlorine, bad taste and odor, and dozens or even hundreds of chemicals that may be lurking in your water source.
Next comes an ion exchange resin. It filters metals – think lead – and hard water minerals.
Stage 6 + 7 is Eagle Redox Alloy filter media, a blend of copper and zinc. They combine electrochemical oxidation & reduction with adsorption. This takes care of hydrogen sulfide, iron, mercury, chromium, cadmium and other dissolved metals. The media also inhibits bacterial growth throughout the entire system.
The semi-permeable membrane (stage 9) rejects all particles larger than 0.0001 micron.
And lastly, filter stage 11 is another GAC filter that removes any residual tastes.
Stages 3, 8, 10, and 12 are filter pads. Rated at 1 micron, they remove suspended particles like silt, sand, rust, sediment, and cyst.
Enough output water flow for family use.
Optional: Ultraviolet light filter. Kills 99.99% of bacteria, viruses, and protozoa.
Optional: Nitrate filter. You may need this if you live close to agricultural lands or animal feedlots.
Optional: Fluoride filter. For high organic fluoride in well water.
No more difficult to install than other under sink RO systems.
Maintenance requirements are kept at a bare minimum. Cost: $100-155 per year. You can subscribe to save 5%.
1-year warranty.
Cons
Installations directions are a bit vague.
No NSF tests.
Our Rating
Filtration Performance: 4.0/5.0
Filter Life: 5.0/5.0
Price: 5.0/5.0
Annual Filter Replacement Cost: 4.5/5.0
Overall: 4.5/5.0
Best for
The Crystal Quest 1000C is best for people who want an RO system suited for well water purification.
5. Best for Portability: Crystal Quest Thunder RO System
The Crystal Quest Thunder is our number one portable reverse osmosis system. 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 real issue is that we’re missing NSF testing/certifications with specific contaminant reduction rates. 4.0 stars!
Crystal Quest Thunder Reverse Osmosis Water Filter
Filter Process: GAC, RO, KDF, Ion Exchange, 1-Micron Filter Pads
Membrane Rating: 50 gpd
Filtering Capacity: 1-3 Years
WxHxD: 16″x7″x7″
Water Temperature: 40-85 °F
Operating Pressure: 45 psi Minimum
Warranty: 1 Year
Key Features & Pros
Don’t have much space? Measuring 16x7x7 inches, the Crystal Quest Thunder is one of the smallest and thus most portable RO water filtration systems we know.
10-stage filtration process removes sediment, cyst, chlorine, VOCs, bad taste/odor, pesticides, metals, salts…
Granular activated carbon, RO membrane, copper-zinc redox alloy (KDF), and ion exchange resin are separated by 1-micron filter pads.
Bacteriostatic filter media inhibits fouling.
Filtered drinking water tastes very clean.
Tool-free installation is quick and easy – faucet adapters included.
Replacing the high-capacity filters is child’s play thanks to quick-connect fittings.
Replace granular activated carbon cartridge every 12-18 months, RO membrane and SMART filter every two years, maybe three. Average annual cost: $65-100 which is cheap.
Crystal Quest customer service is great.
High-efficiency unit is covered by a 1-year warranty.
Cons
No NSF certifications. No contaminant reduction rates.
Only fits standard-sized faucets.
System is rated at .03 gallon per minute water flow which equals about 2 gallons per hour.
Not super fast but fast enough when used in combination with a large container to store the purified water in.
Our Rating
Filtration Performance: 4.0/5.0
Filter Life: 5.0/5.0
Price: 4.5/5.0
Annual Filter Replacement Cost: 5.0/5.0
Overall: 4.0/5.0
Best for
The Crystal Quest Thunder is best for people who want a portable reverse osmosis water filter.
6. Best Budget Option: NU Aqua Platinum Series 100-Gallon-Per-Day 5-Stage Reverse Osmosis System
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 120-day satisfaction guarantee (refund or credit of original purchase amount if RO water doesn’t meet your expectations), and a full 3-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
1-micron polypropylene sediment filter rids incoming water of visible particulate matter: Dirt, sand, dust, rust, debris. Extends the life of the other filters in the system.
Clear filter housing allows for easy monitoring.
Granular carbon fiber removes chlorine, pesticides, color, bad taste, odor-causing compounds, and overall finer particles that the first filter stage may have missed.
The thin-film composite semi-permeable membrane rejects even the smallest dissolved solids: Salts, metals like lead, arsenic, fluoride, sulfate, radium…
Before the RO water comes out of the chrome dispenser it passes through an inline post-filter made of activated coconut shell carbon. It removes any last traces of flavor or odor to make sure you get the freshest possible taste.
High flow membrane (100 gallons of water per day) fills tank in less than 2 hours, perfect for large households with up to 6 people.
All parts are BPA-free to keep water as pure as possible.
Almost anyone can install this RO system in one afternoon. Step-by-step installation DVD and owner’s manual included.
Nu Aqua reverse osmosis systems are “a breeze to maintain”.
Change filters about every six months and RO membrane every 1-1.5 years.
Replacement sets are super cheap.
TDS meter as free bonus.
5-stage RO system is backed by 120-day satisfaction guarantee (only when bought on nuaquasystems.com) and full 3-year warranty.
Cons
Written installation directions could do with an upgrade.
Most parts are plastic.
Our Rating
Filtration Performance: 3.5/5.0
Filter Life: 3.5/5.0
Price: 5.0/5.0
Annual Filter Replacement Cost: 5.0/5.0
Overall: 3.5/5.0
Best for
The NU Aqua Platinum Series is best for people looking for a budget-friendly RO filter system.
7. Home Master TMHP HydroPerfection Reverse Osmosis Drinking Water Filter System
Finally, the HydroPerfection, or TMHP, which combines the best of all Home Master systems – a 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 wastewater.
The result is highly-purified and great-tasting alkaline drinking water. You just need to be willing to pay a premium. 4.0 stars!
Home Master HydroPerfection (TMHP) Reverse Osmosis Filtering System
One of the few companies that produces their filter elements in the U.S.
Uses 5-micron sediment pre-filter, 5-micron coconut shell catalytic carbon + KDF-85 pre-filter, DOW FILMTEC RO membrane, UV light filtration, and coconut shell GAC remineralization filter to trap sediment, remove cloudiness, taste, and odor, and reduce contaminants like arsenic, chromium-6, lead, radium, chlorine, chloramine, iron, hydrogen sulfide, and chemicals and organic contaminants including pesticides.
UV filter kills 99.99% of bacteria, viruses, and other microorganisms.
Mineral stage restores calcium and magnesium content (30-60 ppm) for alkaline, great-tasting taste water. Also prevents storage tank degradation.
Non-electric permeate pump reduces water waste from the average four gallons wasted for every gallon of purified water produced down to one.
Faster than normal output water flow from the RO faucet lets you fill a large pitcher in no time.
Easy and straightforward DIY installation. Quick-connect fittings, color-coded tubing, detailed instruction manual + video series, live support.
Modular high-capacity filters are easy to change without tools (replace cartridge + entire housing).
Filters last a full 2,000 gallons of water or one year. Reverse osmosis membrane is good for 3 to 5 years. Yearly replacement cost: Around $150 which is okay taking into account the number of filtration stages.
Modular design prevents flooding and accumulation of germs.
Home Master reverse osmosis systems are backed by 5-year limited warranty + 30-day satisfaction guarantee.
Cons
High initial price tag.
A few people had difficulties with the install.
We would have liked more testing against NSF standards.
Our Rating
Filtration Performance: 4.0/5.0
Filter Life: 5.0/5.0
Price: 4.0/5.0
Annual Filter Replacement Cost: 5.0/5.0
Overall: 4.0/5.0
Best for
The Home Master TMHP is best for people looking for an under sink reverse osmosis water system combining the standard filtration process with UV purification and remineralization.
Buying Guide: How to Choose the Home RO System That’s Best for You
The following are key features worth considering when shopping for an RO system. They will help you choose the right on for your needs and budget.
Reverse Osmosis Systems and NSF Certifications
They may be more important with other water treatment 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.
NSF Standard 42 tests water filtration systems for the reduction of aesthetic non-health-related contaminants, most importantly chlorine. The scope of the standard also includes material safety and structural integrity.
Standard 53 tests systems for the reduction of contaminants with health effects regulated by the U.S. Environmental Protection Agency (EPA). These include cysts, some heavy metals, and volatile organic compounds (VOCs) among others. Again, the scope also covers material safety and structural integrity of a product.
Standard 401 tests filtration systems for the reduction of 15 different “emerging compounds“. These are pharmaceuticals and chemicals not yet regulated by the EPA.
NSF Standard 58 is for reverse osmosis systems specifically. It establishes the minimum requirements for the reduction of a whole range of contaminants, such as TDS (Total Dissolved Solids), chromium 3 and 6, arsenic, nitrate/nitrite, and lead. Material safety and structural integrity are included.
Some reverse osmosis systems are also certified by the FDA which we consider less important.
The Water Filtration Process
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:
2. Carbon pre-filters – Remove tap water disinfectants, organics, chemicals, unpleasant odors and tastes, a few heavy metals, and even cysts if the micron rating is small enough.
3. Granular carbon pre-filters – Same as stage 2.
4. Reverse osmosis membrane – The reverse osmosis membrane rejects more or less all remaining contaminants including salts, metals, bacteria, and viruses.
5. Coconut shell post-filters – Remove any residual taste.
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.
RO Filter Style
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.
Water Demand
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.
RO System Installation and Filter (Membrane) Replacements
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.
Water Pressure and Water Wastage
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.
Cost
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.
Where to Buy
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.
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.
How Does a Reverse Osmosis System Work?
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…
The Different RO System Components and the X-Stage Filtration Process
Pre-Filters
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.
RO Membrane
At stage 2 or 3, the semipermeable membrane comes into play. It more or less rejects all remaining water contaminants including heavy metals, salts, radiation, BPA, and microorganisms. Reverse osmosis even removes fluoride.
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.
Post-Filter
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.
Storage Tank
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.
Automatic Shut-Off Valve
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.
Faucet
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.
Check Valve
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.
Flow Restrictor
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.
Optional Components
Remineralizer
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.
UV Light
An optional UV light stage is great if you’re dealing with microorganisms. The UV light will render them harmless.
Permeate Pump
A non-electric permeate pump improves the pure water:waste water ratio so that less water waste goes down the drain.
Electric Pressure Pump
Electric pressure pumps also lower the amount of water waste while boosting overall water production.
About Reverse Osmosis System Efficiency Ratios
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.
What Do Reverse Osmosis Filtration Systems Remove from Water?
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:
Sediment
Water disinfectants (e.g. chlorine, chloramine)
Disinfection byproducts (e.g. TTHMs)
Volatile organic compounds
Nitrite/nitrates
Pesticides
Herbicides
Heavy Metals (e.g. lead)
Metalloids (e.g. arsenic)
Transition metals (e.g. chromium 6)
Salts & minerals
PFAS
Emerging chemicals/pharmaceuticals (e.g. BPA)
Microorganisms (bacteria, viruses, cyst)
Overall TDS
What Does TDS Mean?
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 Home Reverse Osmosis System Worth It? – Pros & Cons
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.
Reverse Osmosis Water: Risks
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.
How to Remineralize RO Water
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.
Do You Need a Reverse Osmosis Filtration System?
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.
And doing your own testing at best can only give you a very rough idea of what you’re facing.
How to Install a Reverse Osmosis System
Location
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.
Tools & Supplies
Do yourself a favor and gather all the necessary tools and supplies before you start with the actual installation:
Power drill
¼” (⅜”) (½”) drill bit (size depends on faucet type used)
Screwdriver
Tubing cutter
Utility knife
Adjustable wrench
Towel
Bucket
Installation Process – Step by Step Instructions
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.
1. Faucet
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.
2. Drain Saddle
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.
3. Feed Valve
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.
4. Storage Tank
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.
5. Set Up RO Module
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.
6. Filter Elements
Install the different filtration elements including the reverse osmosis membrane as instructed in the manual.
For regular filters, remove housing, insert cartridge, screw housing back, and carefully tighten with wrench.
For RO membrane, remove housing cap, push membrane into socket, and put housing cap back on.
7. Finishing the Installation
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.
Reverse Osmosis Water Filter Maintenance
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.
RO Water Filter Changes
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:
Close the incoming water and storage tank valves.
Depressurize.
Remove filter housings.
Insert new filter cartridges.
Screw housings back on.
Open valves.
Flush new filters while checking for leaks.
Membrane Replacement
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.
System Cleaning
Although not necessary in all cases, ideally you want to clean (and sanitize) your reverse osmosis water filtration system once a year.
Start by removing all filter elements.
Scrub the inside of each filter housing with warm dishwater and rinse afterwards.
Optional: For sanitizing, add unscented household bleach into the housing of filter stage one. Then screw all other empty filter housings back on. Allow the storage tank to fill and let the bleach to stay in the system for at least 30 minutes. Flush the entire tank. Let the tank refill a second time and flush out. While you wait: Soak the RO membrane in the right chemical solutions as recommended by the manufacturer to prevent fouling and scaling.
Reinstall all filter elements.
Frequently Asked Questions (FAQ)
How long do reverse osmosis filters last?
This depends on your water source and water usage. An RO system that produces nothing but drinking and cooking water can last a long time – up to several years.
Is an RO filtration system worth the money?
Absolutely, if you want high-quality water.
What is the pH of reverse osmosis (RO) water?
The pH of most RO waters is slightly acidic. That’s because it lacks minerals like calcium and magnesium. We suggest remineralization before use which will raise the pH.
How much does it cost to install a reverse osmosis system?
Portable RO filters are installation-free so it costs nothing. As for under sink water systems, prices start at $150. You can also do this yourself if you’re not afraid to drill a hole in your kitchen counter and drain pipe. If you decide to hire a plumber make sure to reach out to more than one company so that you can compare estimates.
Standard RO system or water softener?
Quality reverse osmosis water filters filter water and remove up to 99 percent of contaminants; a water softener takes care of water hardness – two entirely different things.
Questions? Ask away!
About the Author Alexandra Uta
Alex is a content writer with an affinity for research and a methodical attention to detail. Since 2020, she has fully immersed herself into the home water treatment industry only to become an expert herself. Alex has been using water filters and similar products for years which has gained her lots of hands-on experience.
Learn more about Alex and the rest of the BOS Team.
Information provided on BOS is for educational purposes only. The products and services we review may not be right for your individual circumstances.
We adhere to strict editorial guidelines. Rest assured, the opinions expressed have not been provided, reviewed, or otherwise endorsed by our partners – they are unbiased, independent, and the author’s alone. We fact-check all content for accuracy. It is accurate as of the date posted and to the best of our knowledge.
Leave a Comment:
Carl says
May 30, 2017
Hello,
I am wondering if the Home Master RO systems are from the same manufacturer as the Tap Master systems that I used a couple of years ago. The quality was really nice and the processed water’s purity level was that high that the water almost tasted sweet.
Thank you for your question. Actually, the Tap Master brand was renamed to Home Master. As far as I know the manufacturer considered it to be more suitable to convey the right message to their customers. So typical marketing strategy. I don’t think that they actually came up with a lot of new product features. Though, as you already said, Home Master (or Tap Master) has set the bar really high for years…
thanks for doing the work and collecting all that information. I listened to your advice and bought the APEC Essence with 50 gpd and couldn’t be happier with it. After 2 months of using the system everything still works exactly as it should. The water is very delicious.
Thank you for your kind words. We’ve put a lot of effort into creating this site and still continue do so. It’s nice to hear that the information was useful to you :).
Hey everybody! Just wanted to reach out to you and say thank you for the free info you provide. You guys literally saved me from hours of research and browsing the web. Thumbs up and keep up your great attitude 😉
Hi, I would be interested to know what you guys think about demineralized water, which according to multiple sources that can be found on the web, could actually be harmful to our health.
Before I can give you my opinion on the topic, I want to point out that I’m no doctor whatsoever and therefore can’t give you any medical advice!
It is true, a number of sources online make that claim you are talking about. First of all, you need to know that we only get about 5% of our daily mineral intake from drinking water. We digest the remaining 95% from our food. Therefore it is important to eat a sufficient amount of healthy foods that contain those minerals. Furthermore, what you can do is use a remineralization stage to get those minerals back into your drinking water in case you are still concerned.
After that Flint crisis a couple of years ago I’m most concerned about lead. Can you tell me how I can get more information on the drinking water where I live (in Wisconsin)? I would like to find out about what poisonous stuff can be found in there. Also do you have a system that you can specifically recommend for removing lead?
The quality of water that you’re receiving depends on what water utility your home is connected to. There are hundreds or even thousands of utilities in Wisconsin, so I cannot answer your question, I’m afraid. But what you can do is use this database: https://www.ewg.org/tapwater/index.php. Just enter your zip code and hit enter and chances are that you will find your water utility there. Unless you are getting your water from a private well. The database doesn’t cover those, unfortunately.
Regarding water filters suited for lead removal, check out our article section in the sidebar. We’ve recently added a new article with the topic ‘What’s the Best Water Filter for Lead Removal’.
You are claimed in YouTube comments that”we prefer the AquaTru due to its NSF certifications” which is misleading and false. AquaTru do not have NSF certifications for counter top at all. They are certified by IAPMO to NSF standards thats all.
Hello, I just watched Sara’s video on the 10 best countertop RO systems. She did an honorable mention on the BlueVua except there were no findings of the tests being NSF certified. I was wondering your thoughts or knowledge of the BlueVua ROP Lite system (the smaller unit)? It has all four cartridges compressed into one cartridge. I was wondering if you believe it is just as effective or less so? I saw Sara’s video after a week of owning the BlueVua Lite and just second guessing my purchase. Thank you in advance for your response. Wendy
Hi Wendy,
So we haven’t lab-tested the Bluevua ROPOT-Lite. However, because all filter stages are compressed in a single cartridge, I would assume that you get less filter media in total as compared to the regular Bluevua RO100ROPOT. If so, then this could result in lower filtration effectiveness – but please note that this is pure speculation. Again, we haven’t lab-tested the Bluevua ROPOT-Lite.
