Best Reverse Osmosis System Reviews in 2021

best reverse osmosis system reviews

It’s only in recent years that America has started regulating its public water supply – and many people would argue that not enough is being done to protect us from harmful substances. While some contaminants must legally be reduced to trace amounts, there are emerging contaminants – including pharmaceutical drugs and chemicals – that aren’t currently regulated at all. 

Reverse osmosis, as you know, is one of the best means of removing all the bad stuff from your water, with more than 99.99% effectiveness. But we’re inundated with options nowadays, and it’s not always easy to know when you’re getting a good value for money. 

I know exactly how saturated today’s market is. With almost a decade of industry experience under my belt, and with works published in the likes of Water Quality Products Magazine and Simply Recipes, I make water filtration my business. I help 150,000 people just like you find their ideal at-home filtration solution every month. 

Reverse osmosis systems are my specialty. I’ve researched, read up on reviews, and in some cases, contacted the manufacturers and tried these systems in my own home. The resulting list highlights the only 14 reverse osmosis systems that I think are worth your money in 2021. 

In this in-depth guide, I’ve shared:

  • Reviews of my top 13 reverse osmosis systems
  • Guidance on buying a reverse osmosis filter
  • Answers to your FAQs

🥇 Best Reverse Osmosis Systems

  • Waterdrop G3P800
  • AquaTru
  • NU Aqua Efficiency Series Tankless Reverse Osmosis System
  • Aquasana OptimH2O
  • iSpring RCC1UP-AK
  • Home Master TMHP HydroPerfection
  • APEC RO-90 Ultimate Series
  • Express Water Alkaline Reverse Osmosis Filtration System
  • Global Water RO-505
  • Greatwell 400 GPD
  • Olympia Water Systems OROS-50
  • Brondell Circle
Waterdrop G3P800
Waterdrop G3P800
Efficiency Ratio: 3:1
Filtration: 7 stages
Type: Tankless
Water Production (GPD): 800
Dimensions: 18.11 x 5.67 x 17.72 inches
Contaminants Removed: All contaminants >0.0001 microns

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AquaTru Countertop Filtration System
AQUA TRU Countertop Water Filtration Purification System
Efficiency Ratio: 4:1
Filtration: 4 stages
Type: Countertop
Capacity: 1 gallon, 3 quarts
Dimensions: 18 x 18 x 15 inches
Weight: 22.9 pounds
Contaminants Removed: 99% of all contaminants

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👉 Read the full review
NU Aqua Efficiency Series Tankless Reverse Osmosis System
NU Aqua Efficiency Series Tankless Reverse Osmosis System
Efficiency Ratio: 2:1
Filtration: 4 stages
Type: Standard, Tankless
Water Production (GPD): 600
Dimensions: ‎27 x 16.9 x 13.7 inches
Weight: ‎31.9 pounds
Contaminants Removed: 1000+

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Aquasana OptimH2O
Aquasana OptimH2O
Efficiency Ratio: 1:3
Filtration: 4 stages
Type: Standard, under sink
Water Production (GPD): 13.32
Dimensions: 12 x 4.5 x 12.5 inches
Weight: 12.3 Pounds
Contaminants Removed: 88

👉 Read the full review
APEC ESSENCE ROES-PH75 Reverse Osmosis Water Filtration System
Efficiency Ratio: 1:3
Filtration: 6 stages
Type: Alkaline mineral pH+
Water Production (GPD): 75
Dimensions: 16 x 5.2 x 17.5 inches
Weight: 25 pounds
Contaminants Removed: 1000+

👉 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
Efficiency Ratio: 1:3
Filtration: 7 stages
Type: Remineralizing, UV
Water Production (GPD): 100
Dimensions: 15.3 x 9.1 x 18.1 inches
Weight: 35.3 pounds
Contaminants Removed: 1000+

👉 Read the full review
Home Master TMHP HydroPerfection
Home Master TMHP HydroPerfection Undersink Reverse Osmosis Water Filter System
Efficiency Ratio: 1:1
Filtration: 9 stages
Type: Remineralizing, UV filter
Water Production (GPD): 75
Dimensions: 5 x 15 x 15 inches
Weight: 18.75 pounds
Contaminants Removed: 1000+

👉 Read the full review
APEC RO-90 Ultimate Series
APEC Water Systems RO-90 Ultimate Series
Efficiency Ratio: 1:3
Filtration: 5 stages
Type: Super capacity filters
Water Production (GPD): 90
Dimensions: 16 x 5.2 x 17.5 inches
Weight: 25 pounds
Contaminants Removed: 1000+

👉 Read the full review
Express Water Alkaline Reverse Osmosis Filtration System
Express Water Alkaline Reverse Osmosis Filtration System
Efficiency Ratio:
Filtration: 10 stages
Type: Remineralizing, pH+
Water Production (GPD): 100
Dimensions: 15 x 14 x 5 inches
Weight: 27 pounds
Contaminants Removed: 99% of all contaminants

👉 Read the full review
Global Water RO-505
Global Water RO-505 5-Stage Reverse Osmosis System Water Quality Filter
Efficiency Ratio: 1:4
Filtration: 5 stages
Type: Standard, quick-connect
Water Production (GPD): 50
Dimensions: 14 x 5 x 16 inches
Weight: 17 pounds
Contaminants Removed: 99% of all contaminants

👉 Read the full review
Greatwell 400 GPD
GREATWELL 400 GPD Tankless Reverse Osmosis (RO) Water Filtration System
Efficiency Ratio: 1:1
Filtration: 3 stages
Type: Compact design, under sink
Water Production (GPD): 400
Dimensions: 11 x 8 x 15 inches
Weight: 19 pounds
Contaminants Removed: 1000+

👉 Read the full review
Olympia Water Systems OROS-50
Olympia Water Systems OROS-50
Efficiency Ratio: 1:2
Filtration: 5 stages
Type: Standard, under sink
Water Production (GPD): 50
Dimensions: 16.5 x 16.5 x 19.7 inches
Weight: 24 pounds
Contaminants Removed: Bacteria, Viruses, Chlorine, Lead, Sediment, and Others

👉 Read the full review
Brondell Circle Reverse Osmosis System
Efficiency Ratio: 1:2
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
Contaminants Removed: Pesticides, Herbicides, Fluoride, Lead, Radium & Others

👉 Read the full review

⭐️ Reverse Osmosis System Reviews 2021

Waterdrop G3P800

Waterdrop G3P800

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The Waterdrop G3P800 is a compact, modern reverse osmosis water filter that comes with a smart faucet and a built-in UV light. This system offers a superior performance with three filter stages, including a 7-layer reverse osmosis membrane. 

Unique Features

  • UV light that lasts 50 years and reduces more than 99.99% of bacteria and viruses. 
  • Wastes only 1 gallon of water for every 3 gallons produced. 
  • Scale inhibiting technology that reduces calcium and magnesium and prevents scale formation. 
  • Monitors TDS and filter life with TDS and filter tracker.
  • Slim design, measuring just 5.67 inches across.


Q: Can I Install the G3P800 Myself?

A: Yes. Installation is straightforward and doesn’t require a plumber.

Q: What Can the Waterdrop G3P800 Remove?

A: The system can remove all contaminants bigger than 0.0001 microns, including chemicals, heavy metals, bacteria, viruses, fluoride, and more.

👍 What I Like

  • Delivers up to 800 gallons water/day
  • Efficient performance – pure water to wastewater ratio of 3:1
  • Easy to install and low-maintenance.
  • Tankless, on demand filtration
  • Space-saving design
  • Built in booster pump

👎 What I Don’t Like

  • Can’t be used for well water or connected to your fridge
  • Expensive upfront cost

Why It’s My Top Pick

The Waterdrop G3P800 replaced the G3, which was already one of the most efficient RO systems on the market. With its 3:1 pure- to wastewater ratio, the G3P800 gives even the most efficient RO models a run for their money. The extremely high flow rate and contaminant removal capability we expect make this system the best in 2021.

AquaTru Countertop Reverse Osmosis System


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The AquaTru Countertop Water Filtration Purification System is an independently certified under sink 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. The AquaTru requires no plumbing or installation, and is one of the most convenient countertop water filtration solutions available.

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 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 RO process. This ensures filters can continually flush out, extending their life.

👍 What I Like

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

👎 What I Don’t Like

  • Much smaller holding tank than traditional system
  • Les filtration stages than other systems
  • No remineralizing water filter
  • Not certified by the NSF itself

Read the full review: AquaTru Review

NU Aqua Efficiency Series Tankless Reverse Osmosis System

NU Aqua Efficiency Series Tankless Reverse Osmosis System

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With an impressive 600 gallon-per-day capacity and a space-saving tankless design, the NU Aqua Tankless Reverse Osmosis System is ideal for anyone on the hunt for an efficient, compact reverse osmosis unit. 

This system offers four stages of reverse osmosis filtration: a PP/CB filter (which offers two stages of filtration in one), a granular activated carbon filter, and a semi-permeable reverse osmosis membrane. 

The PP/CB filter has a 6 month lifespan, while the GAC filter lasts for 12 months and the RO membrane lasts for 36 months – an extra year longer than the average RO membrane

In all, the system can remove a broad range of common contaminants, including VOCs, chlorine, rust, sediment, hardness, organic chemicals, heavy metals, and salts. 

With a 2:1 pure to wastewater ratio, the NU Aqua RO System is far more efficient than a traditional reverse osmosis unit. Its tankless design also means you can get fast access to water as soon as you turn on the faucet.

👍 What I Like

  • Space-saving design
  • Efficient pure to wastewater ratio
  • RO membrane has a long lifespan
  • 120 day money back guarantee

👎 What I Don’t Like

  • Some customers had issues installing the smart faucet’s plug
  • Not NSF certified yet

Read the full review: NU Aqua Platinum Series

Aquasana OptimH2O

Aquasana OptimH2O Reverse Osmosis System

Combining reverse osmosis and Aquasana’s Claryum® technology, the OptimH20 is an under-sink reverse osmosis system that can remove more than 95% TDS, including fluoride and arsenic. 

This 4-stage filter is NSF certified to standards 42, 53, 58 and 401, for the removal of lead, chlorine, emerging contaminants, and more. 

The OptimH20 comes with a dedicated faucet to prevent metal leaching. It has a storage tank that holds filtered water ready for use.

There are 4 filters used in the OptimH20: a carbon pre-filter, an RO membrane, a Clayrum filter, and a remineralizer. 

The carbon filter uses absorption to remove pesticides, herbicides and other chemicals, while the RO membrane filters out impurities smaller than 1 micron, including nitrites and fluoride. 

The Claryum filter uses catalytic and activated carbon to remove chlorine and lead. The remineralization filter adds healthy minerals like magnesium and calcium back into water. 

You may choose to install the OptimH20 yourself, following the instructions in the user manual. However, installation may be too tricky if your DIY skills are limited. 

You’ll need to change the filters every 6-12 months. The OptimH20 comes with a 3-year warranty and a 90-day money back guarantee.

👍 What I Like

  • Average 1:3 efficiency ratio
  • Removes more than 95% TDS
  • User manual is clear & helpful

👎 What I Don’t Like

  • Lots of filters to change
  • Some customers had problems with water flow

Read the full review: Aquasana OptimH2O review (updated: 2021)



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 and magnesium 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 supply while still maintaining the alkaline taste.

👍 What I Like

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

👎 What I Don’t Like

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

Read the full review: APEC ROES-PH75

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 under sink 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 RO system comes with an advanced UV light filter kit, which inactivates up to 99% of bacteria and viruses from contaminated sources. This makes it possible to use well water, lake, stream or even contaminated city 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 purified water produced, 3 gallons of water are lost.

👍 What I Like

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

👎 What I Don’t Like

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

Read the full review: iSpring RCC1UP-AK

Home Master TMHP HydroPerfection

Home Master TMHP HydroPerfection​ review

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

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

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 a standard household water or well water supply.

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

This reverse osmosis filtering system includes a permeate pump that increases pressure. 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.

👍 What I Like

  • Thorough filtration ideal for treating well water
  • Remineralizing filter adds calcium & magnesium back to filtered water
  • Simple installation DIY
  • Permeate pump included
  • Long-lasting filters

👎 What I Don’t Like

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

Read the full review: Home Master TMHP HydroPerfection

APEC Water Systems RO-90 Ultimate Series​

APEC RO-90 review

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

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

Designed, tested and assembled in the US, the APEC RO-90 Ultimate Series Top Tier has been a WQA Gold Seal certification 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.

👍 What I Like

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

👎 What I Don’t Like

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

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

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

👍 What I Like

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

👎 What I Don’t Like

  • 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

Global Water RO-505​

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

The Global Water RO-505 is a 5 stage RO 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 that removes 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 six months up to 12 months, depending on water quality and level of use. The system 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. 

👍 What I Like

  • Pre-assembled allows super easy installation
  • Great value for money – filters last at least six months
  • 4 extra filters included

👎 What I Don’t Like

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

Read the full review: Global Water RO-505

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 design, this system looks smart and saves countertop or cupboard space.

The RO system produces thorough filtration results with a 3 stage water purification filter that removes up to 99 percent 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.

👍 What I Like

  • Compact space saving design
  • No external storage tank
  • Extremely easy to install and change filters
  • Produces 400 gallons per day

👎 What I Don’t Like

  • 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

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 needs replacing every two years, and the post carbon filter around 1 to 2 years. 

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

👍 What I Like

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

👎 What I Don’t Like

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

Read the full review: Olympia Water Systems OROS-50

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 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 ensures the system can produce a larger quantity of water with less water waste. 

Easy installation and maintenance, with everything needed for installation included, the Brondell Circle RO 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 you about filter changes 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.

👍 What I Like

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

👎 What I Don’t Like

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

Read the full review: Brondell Circle Reverse Osmosis System

🧾 Reverse Osmosis System Buyer’s Guide

I know how difficult it can be deciding whether or not you need to install an RO 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.

I’ve covered everything you need to know to help you make the most informed decision.

If you’re considering buying an RO system, you’ll want to understand exactly how reverse osmosis works, 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 I’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 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.

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.

👍 Benefits Of Reverse Osmosis Filter Systems

Reverse osmosis filtration systems are 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 chlorine, pesticides, nitrates, bacteria, fluoride and even arsenic.

The only way to remove these impurities is by filtering them – and reverse osmosis systems remove all the bad stuff, guaranteed.

Improves Taste

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 sulfide 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

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, especially with the more modern countertop systems.

Nobody wants to spend hours maintaining their water filtration equipment, and with the best reverse osmosis 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.

🧫 Contaminants Removed By Reverse Osmosis Filters

When it comes to any type of water filtration, the more effective methods will be proficient in removing a higher percentage of TDS 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 healthy minerals, salt, pesticides, cations, metals, and other substances that might have made it into your drinking water.

It is impossible to find a water filtration system that can fully remove 100% of TDS from water.

However, reverse osmosis filtration systems offer 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.

TDS in water

💭 Considerations When Purchasing An RO System

Water Source

Your well water or city 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 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 in water filtration systems can only work effectively when enough pressure is applied to force the water through the semi-permeable membrane (the RO filter) to the other side.

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

Storage Capacity

You’ll find that some RO filters have a high-capacity tank that can store up to 75 gallons of filtered water – but keep in mind that paying more for water filtration systems with a bigger tank isn’t always necessary.

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

Remineralization Needs

Some people enjoy being able to drink certain healthy minerals in water, which can be good for our health. These include magnesium and calcium.

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 healthy minerals are important to you. You can do this by adding a few minerals back into your water, or adding an extra filter to your RO system, which will add these beneficial minerals back for you.

Replacement Filters

Even the best reverse osmosis system will require some basic maintenance if you want to keep it working at its 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 water filters in a little more detail.

Untreated water first flows into the RO filter tank through a combination carbon and 5-micron sediment filter cartridges. The role of the carbon filter is to remove chemicals from the water, including chlorine, or fluoride from well water or municipal water.

At the same time, the 5-micron sediment filter removes the larger portions of the sediment in the water, which could damage the semipermeable 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 – the systems feed water in one end, which flows out the other end where the wastewater is flowing out through a drain. 

When the purified water reaches the tank for storage, it can be used when you turn on your faucet. When this happens, the now high-quality water passes from the tank through one last carbon filter, then flows to the faucet that you’ll have installed at your kitchen sink.

The Reverse Osmosis Process: Step By Step

Typically reverse osmosis water filters follow a basic 5 step process. When you see RO systems 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 RO systems, it needs to undergo sediment removal. Sediment filters remove charge particles from your water at this stage, including sand, dirt and rust.
  2. First carbon filter – This filter will remove impurities that would otherwise damage the semi-permeable membrane, such as chlorine and other chemicals. It can also improve the odor 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 – It’s becoming more common for RO systems to have at least a second filter for maximum efficiency. A second carbon filter will help to ensure that the greatest quantity of particles are removed. 
  4. Reverse osmosis membrane – The RO membrane is at the heart of all reverse osmosis systems. Because the membrane contains thousands of tiny holes, the water molecules can pass through the membrane under pressure, but any larger contaminants stay behind. 
  5. Impurities removed – The impurities flow out of RO systems through a separate pipe, so there’s no risk of the particles finding their way back into the purified water.
  6. Remineralization – You can look to add a remineralization filter to your RO system, which can add in healthy minerals like calcium and magnesium, balancing the water’s pH and improving its taste.
  7. Optional step: UV light filter systems – One optional addition you can make to your RO system is to add a UV light. The purpose of a UV light is to make sure your water is microorganism-free, improving water quality further.
RO system diagram

Reverse Osmosis Water Efficiency Ratio

The wastewater ratio of your reverse osmosis system determines the amount of water that is being filtered through the semi-permeable membrane in comparison to how much wastewater containing harmful contaminants is being lost down your drain. The less water is wasted during the RO treatment, the more efficient a unit is.

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

If you want to get the most back from your RO 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.

✅ The Components Of A Reverse Osmosis System

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

Pre Filter

Pre-filters are essential in all reverse osmosis systems. The role of pre-filters is to filter water by removing 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 RO system is the semi-permeable membrane, which traps unwanted elements of unfiltered water, including harmful contaminants like pesticides.

reverse osmosis semipermeable membrane diagram

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, an RO 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

The speed at which an RO filter can feed water through its filters can affect how much purified water 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. Figure out a gallon per day calculation to learn the right size storage tank you need for continuous access to water.

Remineralization Filters

Because RO filters remove all particles from water, they also remove minerals like calcium, magnesium, iron and zinc. 

We can get these minerals from our food, but it’s handy to be able to obtain them from our water, too – which is where remineralization comes into play.

A remineralization filter allows for minerals to be added back into the filtered water before it reaches the tank for storage.

reverse osmosis remineralizing filer


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 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.

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 RO process.

Electric Pump

Electric pumps work very similarly to permeate pumps in RO systems, 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 for RO systems 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 (and high quality water) 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. If you’re using another water treatment system before your RO system, such as a water softener for treating hard water, be aware that this may affect water pressure somewhat.

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. You can only allow cold water through an RO system, however, as hot water could damage the filters.

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’s fairly easy to install a system 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.

under sink reverse osmosis system

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 RO 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. At this stage, you should also install a shut-off valve if your system has one.
  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. 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.

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.

Maintenance and Changing Filters

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

As well as changing your filters, RO systems require cleaning out every half a year to a year with hot, soapy water. The tubing and housing can be washed, but don’t wash any of the filters or the membrane.

❕ The Verdict: Which Reverse Osmosis System is the Best?

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; some may be made more cheaply than otherss and some may allow for more water per day to be filtered. It’s best to take these differences into account when considering what reverse osmosis system is right for you!

❔ Frequently Asked Questions

How much does a reverse osmosis system cost to install?

If you need to hire a plumber to install your system, there’ll be an extra fee to factor in for the service, usually between $100 and $350.

How long does a reverse osmosis system last for?

The quality of your reverse osmosis system will determine how long the filters last 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 waste water 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.

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 better than their competitors out there.