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Best Reverse Osmosis Systems of 2023

Want purer water? You might want to think about getting a reverse osmosis system.

If you are concerned that your home’s water supply isn’t as pure as it should be, you have numerous water-softening and conditioning systems to choose from. Reverse osmosis systems are currently the industry standard, as they are low-maintenance and highly effective.

Reverse osmosis systems are available in various forms, with some that fit under your sink, on your countertop, or are attached to the main water supply for the entire home. With so many options, it can be daunting trying to find the right system.

We have reviewed ten of the leading products to help you find the best reverse osmosis system for your home. We chose these systems based on their installation type, flow rate, and whether or not they are tankless.

Our Top Picks

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Product Comparison Table

Product Image of the APEC Top Tier RO Drinking Water
Best Overall RO System
APEC Top Tier RO Drinking Water
  • Four-gallon tank
  • Comprehensive installation guide
  • Filters 75 to 90 gallons per day
Product Image of the iSpring Deluxe RO System
Best Under Sink RO System
iSpring Deluxe RO System
  • Can be connected to appliances
  • Simple push connections
  • Filters can be replaced independently
Product Image of the PureDrop RO Water System
Best Budget RO System
PureDrop RO Water System
  • Five-stage filtering
  • Should fit under any sink
  • FDA-approved materials
Product Image of the Home Master Undersink RO Filter
Best RO System for Well Water
Home Master Undersink RO Filter
  • UV filter
  • Battery-operated pump
  • Replace entire filter housing
Product Image of the Express Water House Filter
Best Whole House RO System
Express Water House Filter
  • Pressure gauges included
  • Can process 900 gallons per hour
  • Three-stage filtration
Product Image of the APEC Water Systems RO-90
Best RO System for Hard Water
APEC Water Systems RO-90
  • FDA-certified
  • 75 to 90 gallons per day
  • Lifetime technical support
Product Image of the Brondell RO Circle Filter
Best Compact RO System
Brondell RO Circle Filter
  • Water-saving technology
  • Auto filter-flushing
  • Compact 1.58-gallon tank
Product Image of the Reverse Osmosis RO System
Best Portable RO System
Reverse Osmosis RO System
  • Five-stage filtration
  • Filters will last about a year
  • 14-day satisfaction guaranteed
Product Image of the iSpring Commercial RO Water System
Best Commercial RO System
iSpring Commercial RO Water System
  • Filters process 100 gallons daily
  • Pump and gauge included
  • Freestanding frame
Product Image of the PuricomUSA RO Water Filter
Best Countertop RO System
PuricomUSA RO Water Filter
  • Four-filter system
  • Filter change alert
  • No installation required

The Best Reverse Osmosis Systems of 2023

To help you find the best reverse osmosis system for your home, we have reviewed ten of the leading products available today. We chose these systems based on their installation type, effectiveness, and how often their filters need to be replaced.

APEC Top Tier Reverse Osmosis Drinking Water

Best Overall Reverse Osmosis System

The APEC Top Tier under-sink reverse osmosis system has six filtration stages. These include a sediment removal filter, two carbon block filters, a tubular membrane filter (TMF), a coconut shell carbon filter, and a calcium carbonate replacement filter.

These filters can remove impurities including arsenic, fluoride, chromium, lead, and bacteria, among others. The final filter is made in the United States and adds food-grade calcium minerals to the processed water. This results in drinking water that is free from contaminants but still contains minerals with proven health benefits.

What We Like

Good Sized Tank

The system includes a water storage tank with a capacity of 4 gallons. This means your filtered water will be available on tap whenever you need it.

Easy Installation

The package contains all the parts and tools required to install the system:

  • Detailed manual
  • Dedicated wrench
  • Tank ball and feed water valves
  • Drain saddle
  • Teflon tape

The fittings are designed to connect quickly and there is a flow restrictor that should stay clog-free. All the tubing is of food-grade quality, and the faucet is lead-free. This means the water shouldn’t be contaminated by the system itself.

The manufacturer has uploaded several instructional videos to guide you through each stage of the installation process.

High Capacity

Depending on your water pressure, this system can filter between 75 and 90 gallons of water per day. This is based on a water pressure of 50 to 60 psi.

Included Warranty

This system is protected by a two-year extended manufacturer’s warranty, as long as you register your purchase with the company. It also offers free lifetime technical support from qualified water specialists.

What We Don't Like

High Amount of Wastewater

The company advises that this system produces 3 gallons of wastewater for every gallon of filtered drinking water. Some users report that the real figure is even higher, in the 5-gallon range for each gallon of water produced.

Product Specs

Filter Stages 6
System Size 16″ wide x 5.25″ deep x 17.5″ high
Tank Size 4 gallons
Capacity Per Day 75–90 gallons
Weight 27 pounds

Our Ratings

Filtration Efficiency
4.5 / 5
Flow Rate
4.5 / 5
Filter Life
4.5 / 5
Installation Ease
4.5 / 5
Total Rating
4.5 / 5

iSpring Deluxe Under Sink 7-Stage RO System

Best Under Sink Reverse Osmosis System

This compact iSpring Deluxe under-sink unit measures 14.5 x 5.2 x 18.5 inches. If you don’t have a lot of space, this should fit in a cupboard below your faucet and can provide about 75 gallons of processed water per day.

It has a seven-stage filter system; five for contaminant removal, one to remineralize, and a UV light to disinfect. These will remove impurities including sodium, bacteria, chlorine, fluoride, and lead. Calcium and magnesium are reintroduced to the water at the sixth filter stage to make it healthier to drink.

The UV light is designed to remove microorganisms from well water supplies. The light won’t waste energy as it has a flow sensor switch that activates it automatically. This also extends the life of the UV lamp.


You will need an electrical outlet nearby to power the UV light.

What We Like

Different Water Outputs

This system includes a heavy-duty brushed nickel faucet that can be mounted on your countertop near your sink. You can also connect the output lines to a coffee maker or ice maker if you want to treat their water.

Easy to Fit

Your purchase includes all the parts you need to install your unit. There are written directions accompanied by illustrations and you can access instructional videos on the manufacturer’s website. iSpring’s technical support team is just a phone call away.

The fittings are color-coded and push-to-connect. This makes it easy to identify what goes where and how to connect them.

Easy-Change Filters

The initial filters are transparent, making it easy to see if any sediment is clogging them and replace them. You will also receive a filter wrench to undo each housing and change the filters.

Every filter can be replaced, but this will generally happen at different times. Check the manufacturer’s recommendations for each filter. Changing them at the appropriate times will ensure your water quality stays high, and your system should last longer.

What We Don't Like

Potential Leaks

Some users have reported leaks appearing from various parts of this system. Thankfully, there is a one-year warranty, so you should be able to have any faulty parts replaced.

Product Specs

Filter Stages 7
System Size 14.5” wide x 5.2” deep x 19.5” high
Tank Size 2.5 gallons
Capacity Per Day 75 gallons
Weight 31 pounds

Our Ratings

Filtration Efficiency
4.5 / 5
Flow Rate
4.5 / 5
Filter Life
4.5 / 5
Installation Ease
4.5 / 5
Total Rating
4.5 / 5

PureDrop 5-Stage RO Drinking Water System

Best Budget Reverse Osmosis System

This PureDrop five-stage RO system is designed for customers with a higher budget. It includes a set of three replacement pre-filters so you won’t need to purchase any more for a year. This is based on the manufacturer’s recommendation to replace the filters every six months.

A lead-free chrome faucet and fittings are also included, so all you need to do is install the system and you’re good to go. The connections are color-coded and quick-connect, and there are double O-rings to reduce the chance of leaks.

What We Like

Five-Stage Filtering

This five-stage system has three carbon pre-filters to remove large contaminant particles and chemicals such as chlorine. Once it has moved through these filters, the water enters the reverse osmosis chamber and passes through a membrane with 0.0001-micron holes. The final stage is a granulated active carbon (GAC) filter, which improves the smell and taste of the water (1).

Compact Design

PureDrop states that this system is compact enough to fit under any sink. The tank is 11 inches in diameter and the reverse osmosis filters are 5 inches wide. This means it should leave some storage space in all but the smallest cupboards.

Safe Materials

The BPA-free materials used in this system all comply with the standards set by the FDA. This means the system’s plastic parts won’t contaminate your drinking water.

What We Don't Like

Small Water Tank

This unit’s relatively small 2.2-gallon water tank means it might not store as much water as you would like. You can always transfer the water into bottles or jugs to store more than the tank will hold.

Product Specs

Filter Stages 5
System Size 15” high x 14” wide x 5” deep
Tank Size 2.2 gallons
Capacity Per Day 50 gallons
Weight Not specified

Our Ratings

Filtration Efficiency
4.5 / 5
Flow Rate
4 / 5
Filter Life
4.5 / 5
Installation Ease
4.5 / 5
Total Rating
4.25 / 5

Home Master Undersink Reverse Osmosis Water Filter System

Best Reverse Osmosis System for Well Water

Iron is a common contaminant in water that comes from wells. It can make your water taste metallic, leave rust stains on your sink or bathtub, and ruin laundry and food (2).

This Home Master under-sink system has a pre-filter composed of coconut shell carbon and KDF85 to remove iron, hydrogen sulfide, and chloramines from water. This should mean better-tasting water for your home. It can also prolong the life of your RO filter, which can otherwise be damaged by these contaminants.

What We Like

UV Filter

In addition to iron, well water can contain many microorganisms. A UV filter eliminates many of these from your water in the final filtration stage. It tackles various viruses, spores, and cysts, making your water safer to drink (3).

Improved Water Pressure

This system is equipped with a battery-operated permeate pump. Home Master claims this can increase water production by up to 50% and reduce wastewater by up to 80%. This is great if you have to deal with low water pressure from a well supply.

The system also has flow restrictors in the company’s patented Fast Flow Kit, which can improve the flow rate to your faucet. You shouldn’t have to wait for the water to reach your faucet.

All-In-One Filter Change

Most reverse osmosis systems have filter cartridges housed in individual units, where you only replace the filter itself. This system’s replacement filters are a single piece, complete with new housings. They only need to be changed annually or after 3,000 gallons of water have been processed.


This Home Master reverse osmosis system arrives pre-assembled. This means you won’t need to worry about fitting the various components together.

A comprehensive instruction booklet with color photos will guide you through installing the system. It also includes a troubleshooting guide.

What We Don't Like

UV Light Stays On

The UV light has no flow switch installed to turn it off automatically when there is no water flowing through. This means it is active constantly, wasting energy and shortening the life of the bulb.

Product Specs

Filter Stages 6
System Size 12” deep x 16” wide x 20” high
Tank Size 3.2 gallons
Capacity Per Day 50 gallons
Weight 17.35 pounds

Our Ratings

Filtration Efficiency
4.5 / 5
Flow Rate
4 / 5
Filter Life
4.5 / 5
Installation Ease
4 / 5
Total Rating
4.25 / 5

Express Water Whole House Water Filter

Best Whole House Reverse Osmosis System

This Express Water system has three high-capacity water filters to remove contaminants — they only need replacing every six to twelve months or after 100,000 gallons of water have been filtered. The system also produces no wastewater so it won’t increase your water bills.

The first of the filters are in a clear housing so you can see sediment accumulating inside them, indicating that they need to be replaced. Each filter is easy to change with housings that twist off. Simply remove one, take out the old filter, put the new one in, and twist it back into place.

What We Like

Pressure Gauges Included

The system is fitted with a pressure gauge for each of the filters. This lets you monitor how your system is performing. If the pressure drops on one filter, it could be a sign that the specific filter needs to be replaced.

Solid Mount

Your purchase includes a solid stainless steel mounting cage. This can be used to mount the system on a wall where it is connected to your water supply. Alternatively, it can be used freestanding on a flat, dry surface.

High Output

This system can process about 0.25 gallons of water per second or about 900 gallons per hour. This is enough to use filtered water from more than one faucet or appliance in your home at the same time. This system apparently doesn’t affect the water pressure in your home even while maintaining a high output.

Three-Stage Filtration

The water that enters this system is filtered three times before it reaches your home’s outlets — it should be installed near the main water supply.

The three filter stages are:

  • Sediment filter
  • Granular activated carbon filter
  • Activated carbon block

What We Don't Like

Not Strictly a Reverse Osmosis System

This system uses pressure to filter your water but it does not have a reverse osmosis membrane. Many filters are touted as whole-house RO systems even though they aren’t. Even among the few whole-house reverse osmosis systems available today, customer feedback is very limited.

This unit still uses a similar process. It can remove chlorine, VOCs, chemicals, and radon from your water supply, as well as odors, colors, tastes, and cloudiness. It doesn’t remove beneficial minerals such as calcium and magnesium, so it could be a better choice for drinking water.

Product Specs

Filter Stages 3
System Size 29.25″ high x 23.5” long x 8.5 inches deep
Tank Size Tankless
Capacity 0.25 gallons per second
Weight 62.8 pounds

Our Ratings

Filtration Efficiency
4 / 5
Flow Rate
4.5 / 5
Filter Life
4.5 / 5
Installation Ease
4 / 5
Total Rating
4.25 / 5

APEC Water Systems RO-90 Ultimate Series

Best Reverse Osmosis System for Hard Water

If you want an American-made product, this one from APEC is designed, engineered, and assembled in the United States. It is FDA-certified as having food-grade tubing and it has a 100% lead-free faucet.

This system has been tested and certified by the Water Quality Association as being capable of removing 99% of water contaminants (4). These include lead, fluoride, chlorine, arsenic, viruses, heavy metals, and bacteria.

APEC states that this system is fully automated and can effectively remove contaminants in homes with very hard water or inconsistent water pressure.

What We Like

Large Filters

This system’s filters have high capacities and are larger than many under-sink reverse osmosis systems. This means they won’t need to be replaced as often.

The first stage sediment filter is made from polypropylene and can remove rust, dust, and other particles. The second and third ones are made from extruded carbon blocks and remove chlorine, bad tastes, and smells. They also remove common chemicals and VOCs.

The fourth stage has a membrane from Dow, an industry leader in high-quality innovation. It can remove 99% of the dissolved solids from your water. These include chromium, lead, fluoride, bacteria, radium, and viruses (5).


APEC has confidence in its products and provides peace of mind with a two-year warranty. It also offers lifetime technical support.

What We Don't Like

Occupies More Room

Although this system’s large filters can process more water, they also occupy more space. This system measures 11 inches by 11 inches by 15 inches, so it will occupy a lot of space under your sink.

Difficult Installation

You might need professional help to install this product, especially if you have no plumbing experience. Many customers found it too difficult to install alone, though some have managed it solo.

Product Specs

Filter Stages 5
System Size 11″ wide x 11″ deep x 15″ high
Tank Size 4 gallons
Capacity Per Day 75–90 gallons
Weight 2 pounds

Our Ratings

Filtration Efficiency
4.5 / 5
Flow Rate
3.5 / 5
Filter Life
4.5 / 5
Installation Ease
2.5 / 5
Total Rating
3.75 / 5

Brondell RO Circle Water Saving Filter System

Best Compact Reverse Osmosis System

If you are worried that you don’t have enough space for a reverse osmosis system, Brondell might have the answer. This compact system can hold 4 filters, with the water tank housed in one unit measuring 13.8 inches by 9.2 inches by 16.5 inches. This means it should fit comfortably into a corner of your under-sink cupboard.

It comes equipped with a sleek chrome faucet that has a built-in LED. This light will alert you when it is time to replace your filters, removing any guesswork.

What We Like

Water-Saving Technology

Brondell claims the patented technology in this unit will waste less water than many conventional reverse osmosis systems. Its circle system eliminates back pressure, resulting in a water loss ratio of 2:1.

It also includes a proprietary smart valve and a flexible water tank that improves efficiency when delivering filtered water.

Auto Filter-Flushing

The membrane filter in the reverse osmosis section of this system flushes automatically. This will prolong the life of the filter and prevent sediment from building up.

Quick Tank Refill

This system’s tank is relatively small at 1.58 gallons. It should recharge in about an hour.


The Water Quality Association (WQA) has awarded this system its gold seal for performance. It also meets the quality standards set by the NSF and ANSI.

What We Don't Like

Slow Flow Rate

Despite reviewers praising the quality of the water this unit produces, some are disappointed by the faucet’s slow flow rate.

Small Storage Tank

This unit’s water storage tank is quite small at 1.58 gallons. It can take between 40 minutes to an hour to recharge, so you can do it during low-demand times.

Product Specs

Filter Stages 4
System Size 13.8 x 9.2 x 16.5 inches
Tank Size 1.58 gallons
Capacity Per Day Not specified
Weight 14.6 pounds

Our Ratings

Filtration Efficiency
4 / 5
Flow Rate
2.5 / 5
Filter Life
4 / 5
Installation Ease
4 / 5
Total Rating
3.5 / 5

Reverse Osmosis Revolution Portable Portable 5-Stage RO System

Best Portable Reverse Osmosis System

If you want a reverse osmosis system for your RV or camper, that can be moved from your faucet to your washing machine, or anywhere else in your home or garden, this is a great option.

This countertop system from Reverse Osmosis Revolution includes an adapter that will fit most faucets. However, there are eight adapters to choose from; if you email the company, they will send you a different one.

While this system is smaller than most at just 14 inches x 6 inches x 6 inches, it can still process 75 gallons of water per day.

What We Like

Five-Stage Filtration

Each filter in this system is designed to connect quickly, making them a breeze to change.

  • Stage 1: Removes rust and dust with a 5-micron sediment filter.
  • Stage 2: A coconut-activated carbon filter removes the more common chemicals and VOCs. It also removes chlorine, bad tastes and odors, and cloudiness.
  • Stage 3: The third stage is a TFC high-rejection reverse osmosis membrane that removes dissolved solids.
  • Stage 4: The fourth is a deionizing bed that can remove radiation,
  • Stage 5: The final stage is a coconut carbon that prevents any remaining sediment from getting through.

Long-Lasting Filters

The company claims that its filters should last eight to twelve months or 1,000 gallons of water. This should mean less money spent on replacement filters.

Satisfaction Guarantee

If you purchase one of these systems and quickly decide that you aren’t happy with it, the company offers a 14-day, 100% satisfaction money-back guarantee.

What We Don't Like

Slow Water Production

The flow of filtered water from this unit can apparently be slow. It is probably worth using a water pitcher to collect the water ahead of time, so it is ready when you need it.

Product Specs

Filter Stages 5
System Size 14 x 6 x 6 inches
Tank Size Tankless
Capacity Per Day 72 gallons per day
Weight 5 pounds

Our Ratings

Filtration Efficiency
4 / 5
Flow Rate
2 / 5
Filter Life
4.5 / 5
Installation Ease
5 / 5
Total Rating
3.75 / 5

iSpring Commercial Grade Reverse Osmosis Water System

Best Commercial Reverse Osmosis System

Reverse osmosis systems are a great addition to an office, restaurant, car wash, or home for brewing drinks, watering plants, or filling aquariums. This commercial-grade iSpring unit can provide up to 300 gallons of water per day. That should be enough to provide filtered water for most homes or small businesses.

The system doesn’t include a tank and the high output level means you will need quite a large one. iSpring does sell a 20-gallon tank, or you could purchase a larger one such as this 55-gallon model from Water Prepared.

The system requires a feed water pressure of between 22 psi and 95 psi to be able to filter your water effectively.

What We Like

Oversized Filters

This system’s pre-filters each measure 20 inches and can process about 30,000 gallons of water. There are also three reverse osmosis membranes that can process 100 gallons of water per day. This means the filters won’t need to be replaced frequently, despite filtering more water than most other models.

Pump and Gauge

This package includes a pressure gauge and an automatic booster pump. These will help you monitor the water pressure and ensure the pump is performing effectively.

If the water pressure drops, it often indicates that it is time to replace the reverse osmosis filters. iSpring states that they should last between two to three years.

Freestanding Frame

The entire system is housed in a freestanding frame. This means everything is safely contained, and you should be able to find an appropriate space for it near your water supply.

What We Don't Like

Not a Whole-House System

Like the majority of reverse osmosis systems, this one is designed to fit one water source. Some users overcome this by installing a large water storage tank to provide water throughout their homes. However, you will need some plumbing expertise to do this, or you can hire a professional.

Product Specs

Filter Stages 3
System Size 14 x 10 x 30 inches
Tank Size Not included
Capacity Per Day 300 gallons
Weight 52 pounds

Our Ratings

Filtration Efficiency
4 / 5
Flow Rate
4.5 / 5
Filter Life
4 / 5
Installation Ease
3 / 5
Total Rating
3.75 / 5

PuricomUSA Countertop Reverse Osmosis Water Filter

Best Countertop Reverse Osmosis System

If you want a reverse osmosis filter without a complicated installation process, consider a self-contained countertop unit. This model from PuricomUSA is available in either silver-white or space-black to complement your kitchen’s decor.

There are no hoses or faucet connections, and you won’t have to worry about it occupying cupboard space. You simply plug it in, fill it with water, and you will receive filtered water.

Measuring 9.5 inches by 14.5 inches by 16.25 inches, you will need a suitable surface to place it on. Fortunately, it doesn’t require any clearance at the top or sides as the water is loaded and dispensed from the front of the machine.

What We Like

Four-Filter System

This unit has four filters:

  • 1st: A five-micron sediment filter removes larger particles such as rust and dust.
  • 2nd: A coconut-based active carbon filter block removes pesticides, chlorine, and organic matter.
  • 3rd: The water passes through the reverse osmosis membrane, which can process 75 gallons of water per day. It removes any remaining contaminants such as heavy metals from the pre-filtered water.
  • 4th: The final stage adds magnesium and carbon to the water, improving its taste and mineral content.

Filter Change Alert

A red light on the machine notifies you when your filters need changing. A flashing red light means the pre and post-filters need to be replaced, which should happen approximately every 12 months. A steady red light means the reverse osmosis membrane has expired, which should happen about every 24 months.

No Installation Required

You won’t need any plumbing expertise to use this unit. It is filled with water from your faucet and filters it into a half-gallon tank. The tank takes about 15 minutes to fill and switches itself off when done.

What We Don't Like

Take Care Removing the Reservoir Tank

This system’s wastewater drains back into the empty reservoir tank and needs to be disposed of. Some users reported that it can leak when removed and they needed to place a towel under it to catch the water.

Product Specs

Filter Stages 4
System Size 9.5 x 14.5 x 16.25 inches
Tank Size 0.5 gallons
Capacity Per Day Not specified
Weight 23 pounds

Our Ratings

Filtration Efficiency
4 / 5
Flow Rate
3 / 5
Filter Life
4 / 5
Installation Ease
5 / 5
Total Rating
4 / 5

Product Comparison Chart

Product Best Filter Stages System Size Tank Size Capacity Per Day Weight
APEC Top Tier RO System Overall 6 16″ x 5.25″ x 17.5″ 4 gal. 75–90 gal. 27 lbs
iSpring 7-Stage RO System Under Sink 7 14.5” x 5.2” x 19.5” 2.5 gal. 75 gal. 31 lbs
PureDrop 5-Stage RO System Budget Pick 5 15” x 14” x 5” 2.2 gal. 50 gal. N/A
Home Master Undersink Filter Well Water 6 12” x 16” x 20” 3.2 gal. 50 gal. 17.35 lbs
Express Water Water Filter Whole House 3 29.25″ x 23.5” x 8.5″ Tankless 0.25 gal. p/s 62.8 lbs
APEC Water Systems RO-90 Hard Water 5 11″ x 11″ x 15″ 4 gal. 75–90 gal. 2 lbs
Brondell RO Saving Filter Compact 4 13.8 x 9.2 x 16.5″ 1.58 gal. N/A 14.6 lbs
Reverse Osmosis Revolution Portable 5 14 x 6 x 6″ Tankless 72 gal. 5 lbs
iSpring Commercial Grade RO System Commercial 3 14 x 10 x 30″ N/A 300 gal. 52 lbs
PuricomUSA RO Water Filter Countertop 4 9.5 x 14.5 x 16.25″ 0.5 gal. N/A 23 lbs

What is a Reverse Osmosis System?

A reverse osmosis (RO) system works by pushing water through a semipermeable membrane to filter out impurities. This is similar to the filter in a coffee machine that allows the flavored water to pass through, but not the coffee grounds.

During normal osmosis, clean water slowly moves back to the side where the dirty water is (6). The “thinner” water mixes with the “thicker” water to create equilibrium.

However, in reverse osmosis, the pressure of the incoming water or a pump forces the dirty water through the membrane, reversing the process. The filtered water is collected and sent to your faucet.

Eventually, it becomes difficult for the system to push dirty water through the membrane, and it is drained. It is replaced by fresh water and the process begins again (7).

Reverse osmosis systems can waste a significant amount of water as they usually drain the dirty water into the sewage system (8). They can waste as much as 20% to 30% of the water they process, potentially increasing your water bills (9).

What Does an RO System Remove from Water?

Reverse osmosis systems contain multiple filters that each remove different contaminants from your water. They generally number between two and seven filters (10).

Stage 1

This is a prefilter stage that usually uses a membrane to remove large contaminant particles such as stones, silt, rust, and clay. They prevent particles above a specific size from passing through, usually 5 microns.

Stage 2

A carbon filter is usually used at this point to remove materials such as chlorine, chemicals, and volatile organic compounds (VOCs) from water. These contaminants can alter the taste of your water and could be harmful (11).

Stage 3

A second carbon filter might be used to remove even more particles from the water. This one uses a denser and more compact form of carbon to block even smaller particles.

This means that by the time the water reaches the reverse osmosis membrane, it is already much cleaner. The prefilters can also protect your system and prolong its lifespan, as chlorine and other contaminants could damage the reverse osmosis membrane.

Stage 4

This is the stage where reverse osmosis occurs. The membrane used in this stage can remove even the smallest particles from your water, often anything larger than 0.001 microns, including contaminants such as heavy metals and radioactive material.

During this stage, the contaminated water is directed to the drainage system and the clean water to the final filter stages. Between 93% and 99% of impurities could be removed, including arsenic, fluoride, chlorine, heavy metals, lead, viruses, and bacteria (12).

Stage 5

This is the final step in many reverse osmosis systems and it removes contaminants that can affect the smell and taste of your water. These include chlorine, sulfur, viruses, and bacteria. This stage is usually another carbon filter that is finer than the first two.

If your system doesn’t have any more filter stages, the purified water now moves to your storage tank or faucet.

Stage 6

The filtration stages remove contaminants but they can also remove beneficial minerals. This stage restores some of those minerals to improve the taste and ensure you still receive all the health benefits of drinking water. The minerals added often include calcium and magnesium, both essential for healthy teeth and bones (13).

This stage also alters the pH level of the water. Following the reverse osmosis process, due to the amount of carbon dioxide in the water, it can be slightly acidic (14). By remineralizing the water, the pH balance is restored to about seven or eight, making it neutral on the pH scale (15).

Stage 7

Some reverse osmosis systems have a seventh stage, which uses an ultraviolet filter to disinfect the water. Typically using a UV bulb, this filter can remove viruses, bacteria, algae, and mold spores. It can remove pathogens such as giardia, cryptosporidium, and salmonella (16).

Systems with this final stage will require an external power supply to function.

Additional Stages

Some manufacturers include extra stages beyond the seventh one, but these generally don’t add anything meaningful to the process. They sometimes include reintroducing more minerals to the water.

What is Reverse Osmosis Water Used For?

Water that has been filtered by a reverse osmosis system has several possible uses (17).

Drinking Water

If you spend a lot of money on bottled water, investing in a reverse osmosis system could allow you to produce water of similar quality. Filtered water from an RO system should be contaminant-free, better-tasting, and beneficial for your health.


Impurities in your municipal water supply or well could include chlorine, which can discolor your food and negatively alter its taste. Using water from a reverse osmosis system could improve the taste of your cakes, pasta, bread, and soup.

Clear Ice Cubes

If you have noticed impurities floating around in your glass after ice cubes have melted in it, they could be coming from your water supply. The purified water from a reverse osmosis system should give you clearer ice cubes, making your drink look and taste better.

Washing the Car

As this water has had the minerals filtered out of it, it shouldn’t leave any watermarks if you use it to wash your car.

Pros and Cons of Reverse Osmosis Systems

Reverse osmosis systems have numerous benefits but they aren’t perfect. Let’s take a closer look at some of their pros and cons.


  • No added salt: Many domestic water softener systems use salt as part of the softening process. This can be dangerous if you are on a low sodium diet for health reasons (18). Reverse osmosis filters don’t add salt, making them a safer option.
  • Cleaner appliances: Using water from a reverse osmosis system in appliances such as your coffee maker can reduce mineral buildup and prolong its lifespan. This is especially true if you have a system that does not replace calcium and magnesium — the two main causes of scale (19). If you have a whole house system, your dishwasher, washing machine, showers, pipes, and faucets could all be protected against scale.
  • More effective cleaning products: The reduced pH of reverse osmosis water means its hardness has been removed. This allows your shampoos, soaps, detergents, and dishwashing liquids to clean more effectively (20).
  • Money-saving: Installing a reverse osmosis system can help you save money in multiple ways: you won’t need to buy bottled water, your plumbing appliances should last longer, and you won’t need to use as much soap for an effective clean.


  • One faucet only: Reverse osmosis systems are usually designed to be attached to one faucet in your home. This could be a countertop model or beneath a sink in your kitchen or bathroom.
  • Mineral removal: This doesn’t apply to every model, but the majority of reverse osmosis systems also filter out beneficial minerals. Some add specific minerals back into the water via a post-filter at the end of the process.

Types of Reverse Osmosis System

There are four main types of reverse osmosis systems for commercial or domestic use:

Under-sink systems are designed to fit, unsurprisingly, below a sink in your home, often hidden inside a cupboard. They could have three or more filters in addition to the reverse osmosis membrane. They usually include a faucet that supplies drinking water, a storage tank, and a drain hose for wastewater.


  • Low maintenance
  • Long-lasting filters
  • Good for drinking and cooking water
  • Easy to install


  • Occupies cupboard space
  • Only provides filtered water to one faucet

As the name suggests, this is a reverse osmosis system that sits on your countertop. There are two types to choose from:

  • Attached to faucet: These are a combination of filters that are designed to be attached to your current faucet. They tend to be smaller than their under-sink counterparts.
  • Standalone: This is a standalone unit that you pour water into from your faucet, and it then passes through filters and a reverse osmosis membrane. While this is a compact option, they usually have a small capacity to store the processed water.


  • Can be moved from one faucet to another
  • Some require no fitting; just plug and go
  • Smaller than under-sink systems
  • Ideal for drinking water and ice cubes


  • Lower water output
  • Occupies space on your counter

Although there are whole-house reverse osmosis systems, they are very expensive and have little or no customer feedback. However, there are many excellent whole-house filter units.

These filter units don’t have an RO membrane but they operate on a similar principle, removing chemicals, chlorine, radon, and VOCs from your water supply. They can also remove bad tastes, odors, cloudiness, and discoloration.

An advantage of these systems is that they don’t remove calcium and magnesium, so your water will still contain beneficial minerals. They treat the entirety of your home’s water supply, fitting onto your main water inlet.


  • Easy to install
  • Simple filter change
  • Don’t remove beneficial minerals


  • Not strictly a  reverse osmosis system
  • More expensive than smaller options

Portable systems are very similar to countertop systems. They can easily be moved from one faucet to another, taken with you when you travel, or placed in your RV or camper for road trips.

Like countertop systems, they can be standalone or attached to a faucet.


  • Easy to install and remove
  • Can be taken when traveling
  • Suitable for RVs and camper vans
  • Can be moved from faucet to faucet


  • Filters less water at a time
  • Require more frequent filter replacement

How to Choose a Reverse Osmosis System

There are a few things to consider when choosing a reverse osmosis system:

Flow Rate

Check the water flow rate closely and ensure the unit can supply enough water for your needs and the rest of your household. This is usually specified in gallons per day for countertop and under-sink systems, or gallons per minute for whole house systems.


The number of filters in the system can vary, as can their type. Check that a unit has the right filters to deal with specific water issues. Some will work better for well water with high iron content, while others will remineralize your softened water.

It is worth asking your water supplier for a water quality report before choosing, as this will ensure you cover every base (21).

You should also consider the cost and frequency of replacing the filters. Filters have a limited lifespan and will need to be replaced at some point; smaller filters often need to be changed every three months, while some can be replaced annually.

Tank or Tankless

Decide whether or not you want a tank to store your processed water ready for use. Tanks come in different sizes, so make sure you choose one that is large enough for your needs.

A tankless system can be suitable if you don’t use much water, or if you don’t mind a slight delay when you need water.


Before buying a reverse osmosis system, determine where you will place it and if you have enough room for it. Some systems can be installed relatively easily by following the manufacturer’s instructions.

Ask For Help

If you are unsure how to install your chosen system, you might need to hire a professional to do it for you.

If you are living in rented accommodation, you should also get permission before fitting a reverse osmosis system. If you can’t make any alterations to your plumbing, you could still acquire a countertop RO system.

Water Pressure

If you live in an area with low water pressure, you will need to choose a reverse osmosis system that includes a pump. If it is below 40 psi, it might not be enough to push the water through the membrane (22).

You can contact your water supplier to find out the pressure that is delivered to your home. Alternatively, you can buy a pressure gauge to check it yourself.


Do I Really Need a Reverse Osmosis System?

A reverse osmosis system is essential for drinking water. If you live where tap water is safe, then you don’t need a reverse osmosis system. But if you live where the water may be contaminated you should consider installing a reverse osmosis water purification system.

Reverse osmosis systems are currently considered the best and most efficient water purification methods on the market. They can remove many water contaminants, including asbestos, lead, and more than 80 others.

Suppose you live where the water has high levels of lead, arsenic, or mercury. In that case, you should consider buying a reverse osmosis system.

Can You Drink Reverse Osmosis Water Every Day?

According to WHO, you shouldn’t drink water with a low mineral content for too long. Since reverse osmosis systems can also remove healthy minerals from the water (such as potassium or magnesium), the resulting water isn’t fit for long-term consumption.

How Long Does a Reverse Osmosis System Last?

A reverse osmosis system can last forever if you perform regular maintenance and replace the consumables on time. For example, the membrane of a reverse osmosis system needs to be changed once every two to five years based on the water it has to process.

How Much Does It Cost to Have a Reverse Osmosis System Installed?

The typical cost of installing a reverse osmosis system is $2,200, ranging from $1,000 to $4,800. Systems that perform reverse osmosis at the point of usage typically cost between $150 to $1,300.

A whole-house system will cost considerably more. The price can reach $10,000 if the system is combined with a water-softening package.

How Often Should I Replace Reverse Osmosis Filters?

A replacement of the RO filters has to ideally be performed once every year. This is done to verify that your entire reverse osmosis system is operating at its most efficient level. If you do not follow these steps, pollutants may still be found in the water that you consume.

Does Reverse Osmosis Remove Bacteria?

Reverse osmosis systems efficiently remove many bacteria, including E-coli, Salmonella, and Campylobacter. It’s a water filtration process that removes water contaminants by passing them through a semipermeable membrane.

The membrane’s pores are smaller than the molecules of the contaminants, so they are filtered out of the water. Reverse osmosis is often used to purify drinking water but can also be used for industrial applications.

What Is the Best Reverse Osmosis System to Buy?

The ROES-PH75 is one of the best reverse osmosis systems to buy if you want fresh-tasting water at home.

The ROES-PH75 Essence Series reverse osmosis water filter system is designed with a 75 GPD membrane, a 6-stage filtration process, and a high flow rate of 3.8 Gallons per minute (GPM). It provides the best way to enjoy pure, clean, healthy drinking water for your family.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.