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Best Reverse Osmosis System Reviews in 2020

best reverse osmosis system reviews

Table of Contents

What Is A Reverse Osmosis Water System?

Reverse osmosis is a popular type of water filter that can provide high-quality, safe and great-tasting drinking water. It works by using pressure to push water through a partially permeable membrane, removing impurities and making it clean and safe for drinking.

The best reverse osmosis system removes contaminants such as harmful chemicals, viruses, bacteria, total dissolved solids and more.

Read our reverse osmosis system reviews and learn how to select one for your specific needs with our detailed guide!

Best Reverse Osmosis Systems

Waterdrop WD-G3-W
Waterdrop RO Reverse Osmosis Water Filtration System
Filtration: 7 stages
Type: Tankless
Water Production (GPD): 400
Dimensions: 18.1 x 5.7 x 17.8 inches
Weight: 31 pounds

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👉 Read the full review
APEC ESSENCE ROES-PH75 Reverse Osmosis Water Filtration System
Filtration: 6 stages
Type: Alkaline mineral pH+
Water Production (GPD): 75
Dimensions: 16 x 5.2 x 17.5 inches
Weight: 25 pounds

👉 Read the full review
iSpring RCC1UP-AK 100GPD
iSpring RCC1UP-AK 100GPD High Capacity, Boosted Performance Under Sink 7-Stage Reverse Osmosis Drinking Water Filtration System
Filtration: 7 stages
Type: Remineralizing, UV
Water Production (GPD): 100
Dimensions: 15.3 x 9.1 x 18.1 inches
Weight: 35.3 pounds

👉 Read the full review
Home Master TMHP HydroPerfection
Home Master TMHP HydroPerfection Undersink Reverse Osmosis Water Filter System
Filtration: 9 stages
Type: Remineralizing, UV filter
Water Production (GPD): 75
Dimensions: 5 x 15 x 15 inches
Weight: 18.75 pounds

👉 Read the full review
APEC RO-90 Ultimate Series
APEC Water Systems RO-90 Ultimate Series
Filtration: 5 stages
Type: Super capacity filters
Water Production (GPD): 90
Dimensions: 16 x 5.2 x 17.5 inches
Weight: 25 pounds

👉 Read the full review
Express Water Alkaline Reverse Osmosis Filtration System
Express Water Alkaline Reverse Osmosis Filtration System
Filtration: 10 stages
Type: Remineralizing, pH+
Water Production (GPD): 100
Dimensions: 15 x 14 x 5 inches
Weight: 27 pounds

👉 Read the full review
Global Water RO-505
Global Water RO-505 5-Stage Reverse Osmosis System Water Quality Filter
Filtration: 5 stages
Type: Standard, quick-connect
Water Production (GPD): 50
Dimensions: 14 x 5 x 16 inches
Weight: 17 pounds

👉 Read the full review
Greatwell 400 GPD
GREATWELL 400 GPD Tankless Reverse Osmosis (RO) Water Filtration System
Filtration: 3 stages
Type: Compact design, under sink
Water Production (GPD): 400
Dimensions: 11 x 8 x 15 inches
Weight: 19 pounds

👉 Read the full review
NU Aqua Platinum Series
NU Aqua Platinum Series
Filtration: 5 stages
Type: Standard, under sink
Water Production (GPD): 100
Dimensions: 16.9 x 16.5 x 16.3 inches
Weight: 20 pounds

👉 Read the full review
Olympia Water Systems OROS-50
Olympia Water Systems OROS-50
Filtration: 5 stages
Type: Standard, under sink
Water Production (GPD): 50
Dimensions: 16.5 x 16.5 x 19.7 inches
Weight: 24 pounds

👉 Read the full review
Whirlpool WHER25
Whirlpool WHER25 Reverse Osmosis (RO) Filtration System
Filtration: 3 stages
Type: Standard, under sink
Water Production (GPD): 18.46
Dimensions: 4.7 x 12.2 x 13 inches
Weight: 12.7 pounds

👉 Read the full review
Brondell Circle Reverse Osmosis System
Filtration: 4 stages
Type: Under sink, non-electric
Water Production (GPD): 38
Dimensions: 13.8 x 9.2 x 16.5 inches
Weight: 14.6 pounds

👉 Read the full review
AQUA TRU Countertop Water Filtration System
AQUA TRU Countertop Water Filtration Purification System
Filtration: 4 stages
Type: Countertop
Capacity: 1 gallon, 3 quarts
Dimensions: 18 x 18 x 15 inches
Weight: 22.9 pounds

👉 Read the full review

Further Information

10 best whole house water filters – To learn about the best point of entry (POE) systems, click here.

Under sink or Countertop filters – Compare point of use (POU) drinking water systems.

Water softening systems – If you are trying to solve a hard water problem, learn more.

Best Reverse Osmosis System Reviews 2020

1. Waterdrop WD-G3-W

Waterdrop RO reverse osmosis system review

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The Waterdrop WD-G3-W is a 400 GPD fast flow tankless filtration system that effectively removes most common contaminants from drinking water, including fluoride, limescale, heavy metals and other total dissolved solids.

With a 1:1 pure water to drain ratio, this efficient water system works faster and wastes a smaller quantity of water during the RO process than other reverse osmosis filters. The system doesn’t use a storage tank, preventing secondary water pollution, but produces pure filtered water immediately at the touch of a button, ready for drinking.

The unit can be fitted easily in an under sink area, leaving more cupboard storage space. The system’s internal pump produces purified water at a rate of 400 gallons per day, filtering a cup of water in around 12 seconds.

The Waterdrop RO WD-G3-W contains 3 filters that combine to provide 7 stages of filtration. 


  • Tankless, on demand filtration
  • Space-saving design
  • Built in booster pump
  • Backed by a good customer service
  • High volume of water per day filtered


  • Remineralization water filter adds small quantities of magnesium and calcium
  • May take slightly longer to fill larger bottles or jugs
  • Higher price point

Read the full review: Waterdrop RO


APEC ROES PH75 review

The APEC ESSENCE ROES-PH75 is a 6-stage reverse osmosis system that removes up to 99% of bacteria and other impurities from drinking water.

The unit consists of a 3-stage pre-filter set, a lead-free faucet, and a storage tank amongst other features. To improve the filtered water’s alkalinity and taste and odor, the APEC Essence also includes added calcium minerals from a food grade calcium alkaline inline filter.

With a 2 year extended manufacturer’s warranty. It has a 1:3 waste water ratio, slightly higher than the standard 1:4 ratio that applies in general to reverse osmosis systems.

The APEC Essence is a simple, cost-effective water filtration unit for anyone who wants to improve the cleanliness of their water while still maintaining the alkaline taste. I


  • Simply DIY installation
  • FDA certified components
  • Additional alkaline remineralizing water filter
  • Easy connect to refrigerator


  • May need additional booster or permeate pump 
  • No air gap faucet

Read the full review: APEC ROES-PH75

3. iSpring RCC1UP-AK

iSpring RCC1UP-AK 7-stage review

The iSpring RCC1UP-AK is a superior quality reverse osmosis system that uses 7 stages of filtration to remove contaminants and remineralize water for alkalinity.

With a high efficiency booster pump, the iSpring RCC1UP-AK applies additional pressure, minimizing backflow that can often lead to slower pure water production in other RO systems. This ultimately reduces water waste during the RO process and helps the water storage tank to fill to capacity at a faster rate.

This reverse osmosis system comes with an advanced UV filter kit, which inactivates up to 99% of bacteria and viruses from contaminated water sources. This makes it possible to use well, lake and stream water in the iSpring RCC1UP-AK with the peace of mind that the RO water produced will be clean and safe for drinking.

The system’s filtered water to water waste ratio is 1:3 – for every 1 gallon of water that is produced, 3 gallons are lost.


  • Built in booster pump
  • Alkaline remineralization water filter
  • Built in UV filter
  • Customer service is helpful and responsive


  • More complex installation
  • No option to remove remineralizing water filter

Read the full review: iSpring RCC1UP-AK

4. Home Master TMHP HydroPerfection

Home Master TMHP HydroPerfection​ review

The Home Master TMHP HydroPerfection is an under sink reverse osmosis system that uses advanced filtration and purification sages to remove up to 98% of total dissolved solids from drinking water.

With advanced, long lasting filters, the Home Master TMHP HydroPerfection removes common water contaminants like iron, chemicals, heavy metals and other sediment. The system’s filters can produce 2000 gallons of water before they require changing.

While other RO systems usually require a UV filter to be purchased separately, the Home Master TMHP HydroPerfection includes a built-in UV filter to destroy microorganisms in water without the use of harmful chemicals. The filter makes it possible to use this system for standard household water or well water, and can treat water without changing its chemistry.

The Home Master TMHP HydroPerfection remineralizes its produced water, adding calcium and magnesium twice during the purification process for better tasting, less acidic water.

The system includes a permeate pump that increases pressure, preventing the backflow of water that slows down other systems and leads to increased water wastage. The waste to pure ratio in the standard system is 4:1, or 1:1 with permeate pump.

This system provides nine stages of filtration, purification, sterilization, and enhancement to thoroughly clean water and remove impurities and contaminants.


  • Thorough filtration ideal for treating well water
  • Remineralizing filter adds calcium & magnesium back to filtered water
  • Simple installation DIY
  • Permeate pump included
  • Exemplary customer service


  • Additional number of filters makes for bulkier size
  • Higher price point

Read the full review: Home Master TMHP HydroPerfection

5. APEC Water Systems RO-90 Ultimate Series​

APEC RO-90 review

The APEC Water Systems RO-90 Ultimate Series Top Tier is a certified reverse osmosis water filter for providing ultra-safe pure drinking water.

Consisting of a super capacity sediment filter, two carbon blocks, semi-permeable reverse osmosis membrane, and refining coconut carbon filter, this water filtration system combines five total stages for optimal water filtration.

Designed, tested and assembled in the US, the APEC Water Systems RO-90 Ultimate Series Top Tier has been certified by the WQA to remove up to 99% of all contaminants in drinking water, including chlorine, arsenic, lead, heavy metals and much more.

With a 2 year manufacturer’s warranty with registration and great customer service, this RO unit guarantees safe drinking water for better health.


  • Simple, color-coded installation
  • Relatively cheap replacement filters
  • 5 comprehensive stages of filtration
  • Lower price point
  • Great customer service and warranty,


  • May require an additional booster or permeate pump
  • No remineralization water filter included

Read the full review: APEC Water Systems RO-90 Ultimate Series

6. Express Water 10 Stage RO Mineralizing Water Filter

Express Water 10 Stage reverse osmosis system review

Boasting 10 stages of water filtration, the Express Water Reverse Osmosis Filtration System produces the cleanest, healthiest alkaline water without the unwanted chemical contaminants and impurities.

This complex RO system doesn’t only remove up to 99% of chemicals and pollutants like arsenic, lead chlorine, fluoride and bacteria from water – it also remineralizes the water with calcium, magnesium, potassium, and other beneficial minerals your body needs from healthy alkaline water.

The Express Water Reverse Osmosis Filtration System’s simple design makes it easy for users to set up the system without having to waste money on professional installation. 

With a 1 year guarantee, this reverse osmosis system automatically refills its pure water tank whenever water levels drop below full, without the need to manually refill or activate the system. The system fits in most under sink areas and is most convenient when installed at a kitchen sink.

The system can produce 100 gallons per day, meaning water will always be available to flow from the faucet as per the user’s requirements. The unit’s built-in leak stop valve shuts off water flow if a potential leak is detected.


  • Multiple remineralization filters
  • Simple installation
  • Built in pressure gauge allows you to monitor flow rate easily


  • No option to skip remineralization
  • May require purchase of additional booster or permeate pump

Read the full review: Express Water 10 Stage RO Mineralizing Water Filter

7. Global Water RO-505​

Global Water RO-505 5-Stage Reverse Osmosis Filtration System Review

The Global Water RO-505 is a 5 stage reverse osmosis system with 4 extra filters for removing up to 99% of contaminants such as chlorine, bacteria and lead from drinking water.

The filtration unit’s quick connect fittings make for simple and secure installation. The system is compatible with a normal household water pressure range of 40 to 80 PSI, with a pressure of 60 PSI providing the least water wastage and the fastest tank refill time. The filters and RO membrane can purify up to 50 gallons per day.

Included in the system’s setup are a sediment filter, a GAC coconut shell filter, a coconut shell filter, an RO membrane, and an inline filter. These filters work to remove larger particles of sand and dust, chemicals and odors like chlorine, heavy metals, bad mineral substances, and any other rough taste and odor from water.

Filters require replacing after 6 to 12 months, depending on water quality and level of use. It comes with an extra set of filters, so the first replacement will be free.

NSF tested and certified, this system is produced in the US. The system has a water ratio of 1:3, exceeding the standard RO water ratio of 1:4. 


  • Pre-assembled allows super easy installation
  • Great value for money
  • 4 extra filters included


  • Large physical size. Measure before purchasing
  • No remineralization water filter included

Read the full review: Global Water RO-505

8. Greatwell 400 GPD​

Greatwell 400 GPD Tankless Reverse Osmosis Water Filtration System review

The Greatwell 400 GPD is a tankless reverse osmosis water filter that is designed to produce pure drinking water with a wastewater reduction of up to 450%.

Designed seamlessly with a leak-proof water route, easy-change filters and a slim body, the Greatwell 400 GPD can be stored easily in a standard under sink space. With an all-in-one tankless body, this system looks smart and saves countertop or cupboard space.

The RO system produces thorough filtration results with a 3 stage water purification system that removes up to 99% of over 100 contaminants that are often found in unfiltered drinking water, including lead, chloramine, fluoride, bacteria, sodium and viruses.

With a one-year limited manufacturer’s warranty, and lifetime technical support from top customer service, the Greatwell 400 GPD boasts premium quality components that are designed for efficiency and durability. All materials are FDA approved and meet NSF standards.

Filters will need replacing between every 6 months and a year, and cost around $100 in total.


  • Compact space saving design
  • No external storage tank
  • Extremely simple installation and filter change
  • Produces 400 gallons per day


  • Lack of storage tank may not be ideal for some users
  • Water is not remineralized
  • May require additional tubing to connect to refrigerator 

Read the full review: Greatwell 400 GPD

9. NU Aqua Platinum Series

NU Aqua Platinum Series review

The NU Aqua Platinum Series is a high capacity 5 stage reverse osmosis water purifier that offers clean, great tasting, healthy water on demand. With a flow rate of 100 gallons per day, this RO unit produces pure drinking water at double the output speed of a standard reverse osmosis system.

For users looking to test the quality of their filtered water, the NU Aqua Platinum Series comes with a PPM meter to test the level of total dissolved solids left in their water after the reverse osmosis process.

The system filters water through 5 different cleansing stages: the sediment filter, the carbon GAC filter, the carbon block filter, the reverse osmosis membrane, and the post filter. These stages combined allow the system to remove up to 99% of more than 1,000 contaminants found in drinking water, including arsenic, lead, fluoride, chlorine and bacteria.

Depending on the pressure of household tap water, the NU Aqua Platinum Series produces RO water at a rate of approximately 1:2, producing 1 gallon of water for every 2 gallons of water wasted.

While this is higher than the standard ratio of 1:4 for most RO systems, the user can purchase an additional booster or permeate pump if their incoming water pressure is significantly lower than the recommended 60 PSI. This would improve efficiency, speeding up filtered water production and reducing water waste.


  • Built in PPM meter allows you to monitor TDS
  • High 100 gallons per day flow rate
  • Helpful video content for installation included


  • No remineralization water filter
  • Does not work well with water pressures of 45 psi or below

Read the full review: NU Aqua Platinum Series

10. Olympia Water Systems OROS-50

Olympia Water Systems OROS-50 review

The Olympia Water Systems OROS-50 is an NSF certified 5 stage reverse osmosis water filter for providing clean, high-quality drinking water with minimal total dissolved solids.

With a 3.2 gallon storage tank, this RO unit is designed to produce up to 50 gallons per day. The system is compact enough to fit in most under sink cabinets in a kitchen, and can be stored upright or laid flat on its side.

The system features five stages of water filtration: the polypropylene sediment filter, 2 coconut shell carbon block filters, the 50 gallons per day semi-permeable RO membrane, and the coconut shell post filter.

The first 3 filters will require changing every 6 to 12 months for maximum efficiency. The RO membrane tends to last for around 2 to 3 years, and the post carbon filter around 1 to 2 years. 

The operating pressure for this system is 50 – 100 PSI and has a ratio of drain water to reverse osmosis water in this filter is 4:1. The system does not remineralize pure water after the reverse osmosis stage.


  • Great customer support
  • Easy, color-coded DIY installation
  • Dual carbon block filters


  • Does not function well with water pressures below 40 psi
  • No remineralizing filter included

Read the full review: Olympia Water Systems OROS-50

11. Whirlpool WHER25

Whirlpool WHER25​ review

With an extra long-life filter, this system is designed for longer use between filter changes, with an RO membrane that lasts for years. The system’s built-in EX Change Indicator Light notifies a user when filters need changing, ensuring consistently clean water production.

The Whirlpool WHER25 RO system features a space-saving design with a small footprint that won’t take up too much under sink space. The system can be connected to a coffee machine, refrigerator or ice machine to provide quality drinking water to every taste.

Users looking for quality assurance will appreciate that the Whirlpool WHER25 is USA-built and NSF certified, meaning it has been third party tested to ensure it performs as advertised by the manufacturer.

When it’s time for a filter change, the user does not need to switch off water supply to get the job done. The system features a WHEERF pre and post filter, which require changing every 6 months, and a WHEERM membrane, which should be changed every 2 years. The system operates with a 1:4 filtered water to wastewater ratio.


  • Fewer filters creating less hassle during maintenance
  • FDA approved
  • No tools required for installation


  • Not as efficient as other systems
  • Users less mechanically inclined may need to hire a plumber to assist in installation
  • Larger physical size takes up lots of under sink space

Read the full review: Whirlpool WHER25

12. Brondell Circle Reverse Osmosis System

brondell circle review

The Brondell Circle Reverse Osmosis System is a sleek, modern reverse osmosis water filter that produces high quality filtered drinking water while minimizing water waste.

With four separate filters, this system is designed to deliver optimum water filtration, removing industrial and harmful chemicals, including pesticides, herbicides, fluoride, lead, radium, a number of other chemicals, and any bad tastes or odors from water.

Containing a patented water saving technology, the system’s smart valve eliminates back pressure, which is the biggest cause of inefficiency in most standard reverse osmosis systems. This helps the filtration unit to produce a larger quantity of water with less water waste. 

Easy to install and maintain, with everything needed for installation included, the Brondell Circle Reverse Osmosis System is relatively compact in design and fits easily in the space underneath a kitchen sink. 

The faucet’s built-in LED water filter change indicator can alert a user to when a filter needs changing to ensure the unit works efficiently for longer. 

It’s recommended that filters are changed every 6 to 12 months, depending on level of use and water type. The tank requires flushing before initial use, but no additional cleaning is needed.


  • One of the most efficient systems available
  • Compact design& simple installation
  • Automatic water filter flushing


  • No remineralization filter
  • May not fit under all sinks. Measure before purchasing

Read the full review: Brondell Circle Reverse Osmosis System

13. AquaTru Countertop Water Filtration Purification System

aquatru review

The AquaTru Countertop Water Filtration Purification System is a NSF certified reverse osmosis system for the removal of toxins, hormones, microplastics, carcinogens, and other contaminants from unfiltered drinking water.

Consisting of four filter stages, including the all-important reverse osmosis process, this RO water system is convenient for both home and office use, and takes just minutes to set up. While most reverse osmosis units require self-assembly, the AquaTru requires no plumbing or installation, and is one of the most convenient countertop water filtration solutions available. This RO system costs considerably less than a standard reverse osmosis system, while delivering the same quality of clean, pure water.

There’s no need to guess at when filters require changing – the machine’s digital display will let you know when it’s time. Sleek and compact in design, this reverse osmosis system ticks all the boxes when it comes to visual aesthetics.

Compared to other under the sink RO systems, which usually work off a 1:4 water ratio, the AquaTru is more efficient, discarding only around 25% of water as part of the reverse osmosis process. This ensures filters can continually flush out, extending their life.


  • 3-minute setup
  • Sleek visually appealing design
  • Lower price point
  • More efficient


  • Much smaller holding tank than traditional system
  • Les filtration stages than other systems
  • No remineralizing water filter

Read the full review: AquaTru Countertop Water Filtration Purification System

Reverse Osmosis System Buyer’s Guide

We know how difficult it can be deciding whether or not you need to install a reverse osmosis system in your home or not. And once you make that decision, how to sift through the numerous products on the market to find one for your specific needs.

We cover everything you need to know to help you make the most informed decision.

If you’re considering buying a reverse osmosis system, you’ll need to learn a lot before you can go ahead and make a purchase.

You’ll first want to understand exactly how reverse osmosis works, and how a reverse osmosis water filtration system might be relevant for you. You’ll also want to know the basics about under sink reverse osmosis, and how a system is installed.

Finally, it will be good to understand the factors that might affect, and what makes a reverse osmosis system the best, if performance and value for money are important to you.

There’s no need to spend hours trawling through forums and Google-searching the specifics when we’ve covered everything you need to know in one single buying guide below.


What’s Wrong With Unfiltered Water?

Unfiltered water is generally considered safe to drink but it contains a number of harmful chemicals and pollutants that some scientists believe could cause damage to our long-term health.

We put our trust in water treatment facilities to remove the worst of contaminants from water, but their regulations allow for some to remain. Some chemicals, such as chlorine, are even added to water to disinfect it, and remove any micro-organisms that it may pick up during its journey to your home.

In most unfiltered water, you’ll find a combination of contaminants including fluoride, chlorine, lead, arsenic, radioactive substances, copper, PFOA, and pesticides. These can cause a number of underlying health concerns, including fatigue, cognitive decline, digestive and gastrointestinal issues, and even some forms of cancer and brain damage.

Worryingly, we still don’t know how drinking unfiltered water might affect us in the long run. Drinking water that’s been filtered in the reverse osmosis filtering system reduces the risk of all number of health problems, some of which scientists may not even be aware of today.

Benefits Of Reverse Osmosis Filter Systems

Reverse osmosis is one of the most popular water filtration treatments, and boasts a number of benefits that puts it ahead of alternative methods. The advantages of filtering with one of these systems include the following:

Removes Impurities

Water that’s been treated can contain impurities and pollutants, including pesticides, nitrates, bacteria, fluoride and even arsenic.

The only way to remove these impurities is by filtering them – and reverse osmosis is a method that guarantees clean, pure water.

Most RO filter systems also contain carbon filters, which remove chlorine and chloramines. These disinfect water as it moves through pipes to your home, but may cause a number of health concerns when ingested in larger quantities

Improves Taste

There’s no taste quite like that of clean, pure water. You might not realize just what effect unfiltered water’s impurities can have on its taste until you try a sip of filtered water – and then there’s no going back.

There may be a number of reasons why your unfiltered water tastes funny, the worst – a rotten egg sort of flavor – being down to the water’s hydrogen sulphide content or various bacteria.

The best way to get rid of this taste is to get rid of its source, filtering out the bad stuff with a reverse osmosis filtration system.

Easy to Maintain

The problem with some water filtration systems is that they can be a nightmare to clean, and even worse if something needs fixing.

Because a RO system is fairly simple in design, you won’t need to worry about taking everything apart for a stringent regular cleaning process, and nor will it be a fuss to replace something when it’s seen better days.

Nobody wants to spend hours maintaining their water filtration equipment, and with an RO system, you won’t need to.


You might not consider a reverse osmosis water filtration system to be your cheapest purchase, but when you weigh it up against the alternatives, the cost is more than worth it.

You’ll no longer need to spend money buying your own filtered water from the supermarket, which, if you do the math, totals up to be quite a significant yearly cost.

You’ll find that reverse osmosis filtering provides even better-quality water than filtered bottled water at a fraction of the price.

Contaminants Removed By Reverse Osmosis Filters

When it comes to any type of water filtration, the more effective treatments will be proficient in removing a higher percentage of total dissolved solids from the water.

A water’s TDS, or total dissolved solids is the number of substances, both organic and inorganic, that the water contains.

Typically, these include a mixture of minerals, salt, pesticides, cations, metals, and other substances that might have made it into your drinking water, depending on how it is treated locally and how it makes its way to your home.

It is impossible to find a water filtration system that can fully remove 100% of TDS from water, as the process would take far too long, and wouldn’t be considered a good value for money from a consumer’s perspective.

However, reverse osmosis is a particularly effective means of water filtration that can generally remove at the very minimum 75% of total dissolved solids from water. The best reverse osmosis systems may even be able to remove between 90-99% TDS from water.


It’s worth noting that some pesticide molecules are smaller than water. This means these particles can pass through the semi-permeable membrane, making it impossible for the initial reverse osmosis process to filter them out completely.

However, a number of the modern best reverse osmosis systems now include an additional carbon filtration stage which removes any remaining pesticides from the water prior to drinking.

Considerations When Purchasing An RO System

Water Source

Your water source might have an effect on the reverse osmosis process, depending on the type and number of contaminants it contains.

Generally, the more contaminants your unfiltered water contains, the more difficult it will be for a semi-permeable membrane to filter out these contaminants effectively.

Water Usage

You can expect that reverse osmosis systems for a household or small business, used for the purpose of producing pure drinking water, will filter more water than you consume.

You’ll be fine to turn on the faucet whenever you need a drink, as once you’ve used a certain amount of water, your reverse osmosis unit will get to work creating more clean water to replace what’s been lost.

Average US Household Water Usage

Water Pressure

The reverse osmosis process can only work effectively when enough pressure is applied to force the water through the semi-permeable membrane to the other side.

Low water pressure will lead to a reduced production of filtered water, and may even cause the semi-permeable membrane to become ineffective more quickly.

It’s recommended that reverse osmosis systems have a pressure of around 60 PSI for optimal functioning.

Storage Capacity

When it comes to storage, all reverse osmosis systems are slightly different in what they can hold. You’ll find that some units have tanks that can store up to 75 gallons of filtered water – but keep in mind that paying more for a bigger tank isn’t always necessary.

Keep in mind that your tank will consistently replenish whatever you use, so there’s no need to worry about it running out.

Your reverse osmosis system will be able to refill at a rate of around a gallon per hour, which, for most consumers, is more than enough to keep them going.

Remineralization Needs

Some people enjoy being able to drink certain beneficial minerals in water, which can be fairly good for our health. These include magnesium and calcium, both of which we need to maintain good bone health, ward off diabetes, prevent headaches, provide relief from anxiety symptoms, improve heart health, and much more.

While we can get magnesium and calcium from other sources, obtaining them through drinking water is an easy way to ensure we’re getting our daily mineral requirements.

As reverse osmosis removes all minerals from your water, you’ll have to look at remineralizing your water if certain beneficial minerals are important to you. You can do this by adding a few mineral drops to your water, or adding an extra filter to your RO system. Another simpler method is to take calcium or magnesium supplements in tablet form to make up for what you might be missing from your water.

Replacement Filters

Reverse osmosis systems require some basic maintenance if you want to keep them working at their best. 

Generally, it’s recommended that you change your sediment filter, carbon filter and polishing filter at least once a year, and your semi-permeable membrane every two years.

reverse osmosis system replacement filters


How Does a Reverse Osmosis Water Filtration System Work?

Let’s look at reverse osmosis filters in a little more detail. The process begins in the area of the unit that’s connected to the cold water system which feeds your whole house. The water comes in at this end of the unit, where it can be filtered before it reaches your taps for drinking.

The untreated water first flows through a combination carbon and 5-micron sediment filter cartridges. The role of the carbon is to remove chemicals from the water, most commonly the likes of chlorine, or fluoride from municipal water. In well situations or in rural applications, often the chemicals in the water are things like herbicides or pesticides, which may have entered the water via surface run-off.

At the same time, the 5-micron sediment filter removes the larger portions of the sediment in the water, which could damage the semi-permeable membrane in the later stages of the filtration process.

reverse osmosis filter

The ro membrane is very dense, making it very difficult for the water to get through. It filters out all the larger particles, leaving only high-quality drinking water. The process is continuous – water flows in one end and flows out the other end where the waste water is flowing out through a drain. 

When the purified water reaches the tank for storage, it can be used by you when you turn on your faucet. When this happens, the water passes from the tank through one last carbon filter, which acts as a precautionary filter in case the water has picked up any odors in the tank. Finally, the water will flow to the separate water faucet that you’ll have installed at your kitchen sink.

The Reverse Osmosis Process: Step By Step

Typically reverse osmosis filtration follows a basic 5 step process. When you see a product claiming more than 5 steps, it means the manufacturer has split one of these 5 into sub-steps. Here is a quick overview of how the process works.

  1. Sediment removal – Before water can pass through the semi-permeable membrane in reverse osmosis, it needs to undergo sediment removal. This is the first treatment that your unfiltered drinking water will receive once it makes it into your filtration system. The bigger particles will be removed from your water at this stage, including sand, dirt and rust. These could potentially damage or clog up the semi-permeable membrane and other parts of the system, so they need to be cleared from the water before it can pass onto the next stage of filtration.
  2. First carbon filter – This filter will remove impurities that would otherwise damage the semi-permeable membrane, such as chlorine and other chemicals. All reverse osmosis systems for home contain at least one carbon filter for essential removal of these particles. These filters can also improve the scent and taste of the water, and remove some pesticides and smaller particles that might be able to pass through the semi-permeable membrane along with the water.
  3. Second carbon filter – Not all RO filtration systems contain multiple carbon filters, but it’s becoming more common for a unit to have at least a second filter for maximum efficiency. A second carbon filter will help to ensure that all particles are removed before the water can pass through into the area containing the semi-permeable membrane. 
  4. Reverse osmosis membrane – The reverse osmosis membrane is at the heart of all reverse osmosis systems. Once the water has had larger sediment and particles removed in the previous stages, it will be able to pass through the semi-permeable membrane the most effectively. Because the membrane contains thousands of tiny holes, the water molecules can pass through the membrane under pressure, but any larger particles stay behind. 
  5. Impurities removed – The impurities flow out of reverse osmosis systems through a separate pipe, so there’s no risk of the particles finding their way back into the purified water. The speed at which the impurities are removed generally depends on the pressure applied to the water passing through the semi-permeable membrane, and the temperature of the water in your system.
  6. Remineralization – You can look to add a remineralization filter to your reverse osmosis system, which can add in healthy minerals like calcium and magnesium, balancing the water’s pH and improving its taste.
  7. Optional step: UV filters – One optional addition you can make to your reverse osmosis system is to add UV filters. The purpose of this treatment is to make sure your water is microorganism-free, which reverse osmosis can’t do on a continual basis. When the ultraviolet light is switched on, it kills any bacteria or viruses that flow through it, making it even cleaner and safer to drink.

Most people won’t need to UV-treat their water, because the water that comes into your home has already been treated to make it safe to drink. If you’re using well or surface water for drinking, however, or you simply want to further purify your water, you’ll find a UV light to be a handy addition to your reverse osmosis system. You can purchase one to add on yourself, or inquire about them when you’re arranging for your reverse osmosis system to be installed.


Reverse Osmosis Water Efficiency Ratio

The waste water ratio of your reverse osmosis system determines how much of your water is being filtered through the semi-permeable membrane in comparison to how much wastewater containing harmful contaminants is being lost down your drain. It goes without saying that the less water is wasted during the reverse osmosis treatment, the more efficient a unit is.

You won’t find a set water efficiency ratio for reverse osmosis systems generally, as there are a number of varying factors that affect how well each different system works. The better-quality a system’s parts, and the higher water pressure, the less water will be wasted.

You can expect most RO systems to work on a 4:1 waste water ratio, meaning that for every 1 gallon of water that’s filtered, 4 gallons of wastewater will pass down the drain. 

If you want to get the most back from your reverse osmosis system, you’ll need to look for a unit that is well-designed and operates at a pressure of 60 PSI. Anything below 40 PSI is considered insufficient, and will produce far more wastewater, as there won’t be enough power to push water through the semi-permeable membrane.

The Components Of A Reverse Osmosis System

Even with some knowledge about the reverse osmosis process, it’s hard to imagine what a reverse osmosis system actually looks like. You’ll find that most systems are similar in design, and contain the same sorts of components.

When you’re looking to purchase an RO system yourself, the biggest difference you’ll find is in the quality of the system and the individual parts that make it up. 

components of a reverse osmosis system
Source: Amazon.com

Pre Filter

A pre filter is essential in all of the best reverse osmosis systems. This is where the water from your pipes will enter before it is filtered. It removes larger grains of sediment from the water, like dirt, which could obstruct other parts of the system and prevent it from working as well.

Semi-Permeable Membrane

Undoubtedly the most important feature of the reverse osmosis system is the semi-permeable membrane itself, trapping unwanted elements of unfiltered water, including harmful contaminants like pesticides.

reverse osmosis semipermeable membrane diagram

Post Filter

Just as all reverse osmosis systems have a pre filter, they also have a post filter. Post-filtering takes place once the water leaves the pressurized tank, but before it enters your taps for drinking. The process gives the water one final treatment, which usually removes any remaining carbon, helping to give water the best appearance and taste possible

Shut-Off Valve

Without a shut-off valve, a reverse osmosis system would struggle to function as efficiently. Shut-off valves are usually automatic, and detect when the water tank is full and thus shutting off the system.

Flow Restrictor

Believe it or not, the speed at which water flows through a reverse osmosis system can affect how much purified water actually passes into the storage tank after filtration. The flow restrictor applies pressure to the water and pushes it through the membrane.

Storage Tank

Most reverse osmosis systems have their own storage tanks for holding purified water before use.

Remineralization Filters

Remineralization stage filters are used to replace some of the healthy minerals that are removed during the filtering process.

Because RO filters remove all particles from water, there’s no way to prevent harmless minerals like calcium, magnesium, iron and zinc. 

We can get calcium, magnesium, iron and zinc from our food, but it’s handy to be able to obtain them from our drinking water, too – which is where the remineralization stage comes into play.

The remineralization process allows for minerals to be added back into the filtered water before it reaches the tank for storage. It can be quite easily attached to your existing reverse osmosis system, and contains a number of minerals that absorb back into the water as it passes through.

reverse osmosis remineralizing filer
Source: Walmart.com


When you get a reverse osmosis system installed, you’ll usually have to switch up your faucet for one that comes with your system. This is normally fitted in your kitchen sink for convenience.

Air Gap Faucet

An air gap faucet is sometimes used for providing a literal air gap for the reverse osmosis filtration systems drain. It’s handy for stopping water from being siphoned back into your RO system through the system’s drain connection. 

An air gap faucet requires you to drill a hole in your sink to install it.

It’s worth being aware that an air gap faucet is not essential, and actually, non-air gap reverse osmosis systems tend to be more modern nowadays.

air gap faucet


Permeate Pump

The purpose of a permeate pump is to improve the efficiency of purified water production in a reverse osmosis system. Without this permeate pump, much more water would be wasted and efficiency of the system decreased. A permeate pump itself can help to prevent up to 80% of wastewater.

The permeate pump stores the water containing impurities in a chamber and uses it to produce energy, which speeds up the production of purified water during the reverse osmosis process.

Electric Pump

Electric pumps work very similarly to permeate pumps, but are different in design. The device uses a pressure switch to monitor water pressure in your system’s water storage tank, and turns on a pump to increase water pressure when necessary.

Not all reverse osmosis systems will need an electric booster pump. However, if your water pressure falls below 40 PSI and you want less water waste and more efficiency, an electric pump will be beneficial.

What Might Affect A Reverse Osmosis System’s Performance?

There are a number of different factors that you should take into consideration if you’re looking to get optimum performance out of your reverse osmosis system. Namely, efficiency of operation is affected by the following:

Quality of Components

Cheaper reverse osmosis systems with poorer-quality parts slow down the water filtration process. You may also find that a poorer-quality system has a shorter lifespan and requires more maintenance and upkeep.

Water Pressure

The pressure of the water flowing through the system will determine how effectively water passes through the semi-permeable membrane. Water pressure that’s too low will cause poor operation.

Water Temperature

There’s not a lot you can do about the temperature of the water that flows through your pipes, but usually, the colder the water, the longer the filtration process works. 

Unfiltered Water Contaminant Contents

The more contaminants a water sample contains, the harder RO filters will have to work, which may impact performance.

Installation & Maintenance of Your Reverse Osmosis Filter System

While you might prefer to hire a plumber to install your RO system for you, it isn’t too difficult to do yourself. You can save a lot of money from doing this, and if you’re feeling up for the job, follow the simple step by step system installation process below.

If you’re looking to install a standard under sink reverse osmosis system, these simple steps will help you to do the job correctly. 

Before you get started with the installation, you need to make sure your reverse osmosis system has all the required parts you need for it to work. Make sure your system has all of its key components, including the storage tank, the reverse osmosis unit complete with filters and semi-permeable membrane, and the new faucet for your sink. under sink reverse osmosis system

You should also make sure you have the required tools on hand to help you carry out the installation properly. You’ll normally need wrenches in various sizes, as well as drill, and a screwdriver and removable screw heads in various sizes. 

Here’s an idea of what the instruction manual would include standard under sink reverse osmosis filtration systems:

Step by Step System Installation

  1. Choose your installation location – Your first task is to find a location that’s most appropriate for installing your reverse osmosis water system. In most cases, the system fits nicely underneath your kitchen sink, but you can choose to put it elsewhere if it suits you more. 
  2. Turn off your water – It would be a bad idea to install a filtration system without first switching off your cold water valve. This is usually found under the sink, and is probably connected to copper piping.
  3. Connect your system to your cold water line – Before you do anything else, twist your cold faucet “on” to relieve any line pressure. Next, you can get to work connecting your RO filter to your water line.
  4. Connect your drain line – At this stage, if there’s noticeable corrosion of your drain line, you’ll want to replace it before you continue with installation. If your drain line is fine, you’re good to go. Drill a hole into the outside wall of your pipe, and attach the drain clamp. Tighten the clamp, again being careful not to go in too hard.
  5. Install your faucet – When installing your faucet, it’s usually a good idea to keep it as close to where your previous faucet was as possible. Drill a hole in your sink if you do not already have one. Position your faucet stem inside the hole and make sure the base is in the right location over the sink. Tighten the faucet in place, making sure to align it in the direction you wish to use it (over the sink is the obvious best). Then attach the appropriate tubing to the bottom of the stem.
  6. Put your unit in place – It’s now time to put the unit in the desired location underneath your sink. You might need to hang your system on a wall if there’s no shelf for it to rest on. Connect the units to the piping, and go back for one final check to make sure everything is sufficiently tightened and in place before giving your system a go.

Once you’re sure everything looks good, turn on the cold water valve slowly. Look out for leaks, and if you notice any, turn the water back off and repair them before going again. Your reverse osmosis tank will take several hours to fill, so you’ll need some patience during this period of time. It’s a good idea to continue to check for leaks during the first few hours of use, and make amendments if necessary.

Maintenance and Changing Filters

There will come a time when you’ll need to change your filters in order to keep your whole house RO system working as efficiently as possible.

To change the pre-filters, turn off the system and turn off your cold water valve, then lift the faucet lever to prevent a build-up of pressure in the system. Use a wrench to open the first-stage filter housing, then remove the old filter and replace it with the new one. Finally, hand-turn the housing to close it back up.

If you’re changing your semi-permeable membrane, follow the same instructions as above, turning off the system and your cold water valve, then lifting the faucet lever to prevent a build-up of pressure. Disconnect the tubing from your membrane housing, then remove the cap from the membrane housing and use a pair of pliers to remove the old membrane. Use the same pliers to insert the new membrane and close the cap, turning it clockwise to tighten it.

To change the 5-stage post carbon filter, after you’ve switched off your system and cold water valve, you’ll need to drain the purified water tank. It might take around ten minutes for the tank to drain fully. Next, disconnect the output tubing and remove the existing filter from the membrane housing. Replace as necessary and reattach to the reverse osmosis unit.

As well as changing your filters, it’s also a good idea to clean out your system every half a year to a year with hot, soapy water. Make sure you turn off your system and water supply before taking it apart. The tubing and housing can be washed, but don’t wash any of the filters or the membrane.

The Verdict: What is the Best Reverse Osmosis System?

It’s important that you choose the right reverse osmosis system for your home or business. Make a careful, considered purchase based on reviews, the trustworthiness of the manufacturer, and your own personal requirements. Don’t be afraid to ask more questions if you have them.

Not all RO systems are the same! Some contain a different number of filters, offering a lengthier or shorter water filtration process. Some may be made more cheaply than others, and some may allow for more water per day to be filtered. Its best to take these differences into account when you’re considering what reverse osmosis system is right for you!

Frequently Asked Questions

🛠 How much does a reverse osmosis system cost to install?

You can expect to spend anything between $100 and $300 for an RO system. If you need to hire a plumber to install your system, there’ll be an extra fee to factor in for the service. There is also the cost of yearly filter replacement to consider.

📅 How long does a reverse osmosis system last for?

The quality of your reverse osmosis system will determine how long it lasts for. You might need to replace parts every year or two, such as your filters and storage tank. There’s no need to replace the whole system, only the parts that are worn out.

💦 How much wastewater do reverse osmosis systems produce?

It’s true that a reverse osmosis filter system generally uses more water than it produces, but in terms of waste, it’s not so bad. You won’t see anything noticeable on your water bill after using a reverse osmosis filtration system for a month or two – it’s similar to your other appliances that use water, like washing machines and dishwashers. 

💲 Does an RO system work better if it costs more?

Not necessarily. While systems containing more expensive parts – and therefore costing more – tend to be more efficient and durable, there are some reverse osmosis systems that cost an inflated amount of money, with no evidence to suggest they’re doing anything other than their competitors out there. 

🔬 How important is water mineral content?

There’s been controversy around the mineral content of water for a number of years now. Most people believe that minerals like calcium, sodium and magnesium are good for your health, but some scientists argue otherwise. Generally speaking, there’s not enough evidence to argue for or against it either way, but water mineral content really isn’t as important as it’s made to be. That said, you can always purchase a filter that adds the minerals back into your reverse osmosis water if that’s your preference.

Best RO System Comparison Chart

SystemRelative PriceFiltration StagesTypeWater Production
Waterdrop RO
Tankless400 GPD
$$$6Alkaline mineral pH+75 GPD
iSpring RCC1UP-AK 100GPD
Remineralizing, UV100 GPD
Home Master TMHP$$$$9
Remineralizing, UV filter75 GPD
APEC RO-90 Ultimate Series
Super capacity filters90 GPD
Express Water Alkaline Reverse Osmosis Filtration System
Remineralizing, pH+100 GPD
Global Water RO-505
Standard, quick-connect50 GPD
Greatwell 400 GPD
Compact design, under sink400 GPD
NU Aqua Platinum Series
Standard, under sink100 GPD
Olympia Water Systems OROS-50
Standard, under sink50 GPD
Whirlpool WHER25
Standard, under sink18.46 GPD
Brondell Circle Reverse Osmosis System
Under sink, non-electric38 GPD
AQUA TRU Countertop Water Filtration System$$$4

Countertop54 GPD