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Best Reverse Osmosis Systems of 2022

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

If you’re concerned that your standard tap water isn’t as pure as it could be, there are several water softening and conditioning systems you could choose for your home. If you don’t want to be messing around with adding salt, the best reverse osmosis system could be what you’re looking for.

These filter your water and remove contaminants to give you a better quality drinking water. You can select one that fits under your sink, on your countertop or to the mains supply for the whole home.

Let’s find out how these systems work, what they could do for you and look at our top 10 recommended options in detail.

Our Top Picks

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Product Comparison Table

Product Image of the APEC Water Systems ROES-PH75 Essence Series Top Tier Alkaline Mineral pH+ 75 GPD 6-Stage Certified Ultra Safe Reverse Osmosis Drinking Water Filter System , White
Best Overall RO System
APEC Top Tier RO Drinking Water
  • Good sized tank
  • Easy installation
  • High capacity
Product Image of the iSpring RCC7AK-UV, NSF Certified, 75GPD 7-Stage Under Sink Reverse Osmosis RO Drinking Water Filtration System with Alkaline Remineralization Filter and UV Ultraviolet Filter
Best Under Sink RO System
iSpring Deluxe RO System
  • Different water outputs
  • Easy to fit
  • Easy-change filters
Product Image of the PureDrop RTW5 5 Stage Reverse Osmosis RO Water Filtration System with Faucet and Tank - Under Sink Water Filter Plus Extra Pre Filter Set, TDS Reduction, White
Best Budget RO System
PureDrop RO Water System
  • Five-stage filtering
  • Compact design
  • Safe materials
Product Image of the Home Master TMULTRA-ERP with Permeate Pump Undersink Reverse Osmosis System
Best RO System for Well Water
Home Master Undersink RO Filter
  • UV filter
  • Improved water pressure
  • All-in-one filter change
Product Image of the Express Water Whole House Water Filter – 3 Stage Home Water Filtration System – Sediment, Coconut Shell Carbon Filters – includes Pressure Gauges, Easy Release, and 1” Inch Connections
Best Whole House RO System
Express Water House Filter
  • Pressure gauges included
  • High output
  • Three-stage filtration
Product Image of the APEC Water Systems RO-90 Ultimate Series Top Tier Supreme Certified High Output 90 GPD Ultra Safe Reverse Osmosis Drinking Water Filter System, Chrome Faucet
Best RO System for Hard Water
APEC Water Systems RO-90
  • FDA-certified
  • Large capacity
  • Lifetime technical support
Product Image of the Brondell Circle Reverse Osmosis Water Filter System, Under Sink Water Filter, Black – 4 Stage RO Water Purifier with Designer Chrome Faucet – Quick Change Filter, WQA Gold Seal-Certified
Best Compact RO System
Brondell RO Circle Filter
  • Water-saving technology
  • Auto filter-flushing
  • Quick tank refill
Product Image of the Countertop Portable Universal 5-Stage Reverse Osmosis RO Purification Water System with DI Deionizing Mixed Bed (Close to 0 PPM) postfilter, Build in USA
Best Portable RO System
Reverse Osmosis RO System
  • Five-stage filtration
  • Long-lasting filters
  • Satisfaction guaranteed
Product Image of the iSpring RCB3P Reverse Osmosis RO Water Filtration System, 300 GPD, Tankless, for Residential and Light Commercial usage,TDS Reduction, with Booster Pump and Pressure Gauge
Best Commercial RO System
iSpring Commercial RO Water System
  • Oversized filters
  • Pump and gauge
  • Free-standing frame
Product Image of the AlcaPure Reverse Osmosis Countertop Water Filter by RKIN with Patented High Capacity 4 Stage Technology: Purified Alkaline Water with Superior Taste. No Installation or Assembly Required. Silver White
Best Countertop RO System
PuricomUSA RO Water Filter
  • Four-filter system
  • Filter change alert
  • No installation required

Product Reviews

Taking into account the factors above, along with customer feedback and industry expert views, here are our choices for the top 10 best reverse osmosis systems.

1. APEC Top Tier Reverse Osmosis Drinking Water

Best Overall Reverse Osmosis System

APEC Water brings us an under sink reverse osmosis system with six filter stages. Included are 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 aim to remove impurities including arsenic, fluoride, chromium, lead, and bacteria, among others. The final filter is made in the US and replaces food-grade calcium minerals into the filtered water. The intended overall result is remineralized drinking water that’s free from contaminants.

What We Like

Good Sized Tank

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

Easy Installation

Supplied are all the parts and equipment needed 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’s a flow restrictor that should be clog-free. All the tubing is of food-grade quality, and the faucet’s made from lead-free materials. This means no contamination should be returned to your water from the system itself.

There are also several videos from the manufacturer that can be found online for 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 water pressure of 50 psi or 60 psi. So, provided your water pressure falls within these parameters, you know how much water you can filter each day.

Included Warranty

This system comes with a two-year extended manufacturer’s warranty, but you need to register your purchase with the company. It also offers free lifetime technical support from its qualified water specialists.

What We Don't Like

High Amount of Waste Water

The company advises the wastewater on this system is 3 gallons for every gallon of filtered drinking water produced. Some find this figure to be much 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

2. iSpring Deluxe Under Sink 7-Stage RO System

Best Under Sink Reverse Osmosis System

This under sink unit measures 14.5 x 5.2 x 18.5 inches. When you don’t have a lot of space, this will fit in a cupboard below your faucet and can provide you with about 75 gallons of water a day.

It has a seven-stage filter system; five for contaminant removal, one to remineralize and a UV light to disinfect. We’re told these will remove impurities including sodium, bacteria, chlorine, fluoride, and lead. Calcium and magnesium are reintroduced to your drinking water at the sixth filter stage.

The seventh UV light stage is designed to remove microorganisms from well water supplies. The light is energy-saving as it has a flow sensor switch to turn it on and off with your water flow. This could also extend the life of the UV lamp.

Quick Tip

Keep in mind you’ll need an electrical outlet close by to power the UV light.

What We Like

Different Water Outputs

A heavy-duty brushed nickel faucet is supplied with this system that can be fixed on your countertop near your sink. You can also connect the output lines to a coffee maker or ice maker if you prefer.

Easy to Fit

This system is supplied with all the parts you need to install your unit. There are illustrated written directions, and you have access to instructional videos on the manufacturer’s website. iSpring’s technical support team is also at the end of a telephone call if you need further help.

We like that the fittings of this system are color-coded and push-to-connect. These make it easy to identify what goes where and how to connect them.

Easy-Change Filters

The first-stage filters in the system are transparent, making it easier for you to see any sediment clogging them, and alerting you to the fact they need changing. Additionally, you’re supplied with a filter wrench to undo each housing to change the filters.

All filters can be replaced, but this is generally at different times. Check the manufacturer’s recommendations for each one. Changing your filters at the appropriate time can ensure your water quality remains high, and your system might last longer.

What We Don't Like

Might Spring Leaks

Some find leaks can appear in various parts of this system. Luckily, there’s a one-year warranty with the product, so you might be able to get faulty valves or tubes 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

3. PureDrop 5-Stage RO Drinking Water System

Best Budget Reverse Osmosis System

PureDrop has budgets in mind with this package; included is a set of three replacement pre-filters meaning you don’t need to purchase any more for a year. This is based on the recommendation of the manufacturer of a change every six months.

A lead-free chrome faucet and all 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 designed to be quick-connect, and there are double O-rings in place to cut down on potential leaks.

What We Like

Five-Stage Filtering

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

The result is filtered drinking water that could save you money when compared to buying bottled water.

Compact Design

PureDrop advises us that this system is compact enough to fit under any sink. Placed side by side, the tank is 11 inches in diameter, and the reverse osmosis filters are 5 inches wide. This might also leave room for storage in the cupboard as well.

Safe Materials

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

What We Don't Like

Smaller Water Tank

The smaller water tank on this unit might mean you don’t have as much water stored as you would like. You can always decant the water into jugs as a backup.

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

4. Home Master Undersink Reverse Osmosis Water Filter System

Best Reverse Osmosis System for Well Water

Iron can be an issue for homeowners with a water supply from a well. It might make your water taste metallic, leave rust stains on your sink or bathtub, and color laundry and some foods (2).

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

What We Like

UV Filter

As well as iron, well water can contain many microorganisms. A UV filter can help remove these from your water in the final filtration stage. It deactivates many viruses, spores, and cysts, making your water safer to drink (3).

Improved Water Pressure

This system is fitted with a battery-operated permeate pump. We are told this can increase water production by up to 50 percent and reduce waste water by up to 80 percent. This is great if you’re plagued by low water pressure from a well supply.

The system also has flow restrictors with the company’s patented Fast Flow Kit, which can improve the flow rate to your faucet. No more trickles or waiting for water to come through.

All-In-One Filter Change

Most reverse osmosis systems have filter cartridges housed in single units, where it’s just the filter that you change. With this system, the replacement filters come as one package complete with new housings. They only need to be changed annually or after every 3,000 gallons of water processed.

Readily Assembled

When your Home Master reverse osmosis system arrives, it will already be assembled. You won’t have to think about fitting the jigsaw of pieces together.

A full instruction booklet with color photos to guide you through the installation of your product is also included. A troubleshooting guide is included as well.

What We Don't Like

UV Light Stays On

There’s no flow switch installed in this system to turn off the UV light when there’s no water passing through. This means it burns all the time and could use more energy and shorten 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

5. Express Water Whole House Water Filter

Best Whole House Reverse Osmosis System

This Express Water system has three water filters of a high capacity to remove contaminants — they only need changing every six to 12 months or 100,000 gallons of water filtered. This system also produces no waste water so it shouldn’t increase your water bills.

The first of the filters is in a clear housing so you can see if sediment is building up inside it, indicating it needs changing. All the filters are easy to change with housings that twist off. You remove one, take out the old filter, pop a 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 check how your system is performing. If the pressure drops on one filter, it might indicate that the filter needs to be changed.

Solid Mount

Supplied with the filter is a solid stainless steel mounting cage. You can attach this to the wall to house your system where it’s installed to your water supply. Or, you can leave it freestanding on a flat, dry surface.

High Output

The capacity of this system is about 0.25 gallons per second, i.e. about 900 gallons per hour. The benefit of this is that you can use filtered water from more than one faucet or appliance in your home at the same time. We’re told the system does not affect the water pressure in your home while maintaining a high output.

Three-Stage Filtration

The water entering this system is filtered three times before it passes on to the rest of your home — it’s installed near the main water supply.

The following filters remove contaminants from your incoming water:

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

What We Don't Like

Not Strictly a Reverse Osmosis System

This system filters the water coming into your home under pressure but does not have a reverse osmosis membrane. Many filters claim to be a whole house RO system, even though they’re not. Of the reverse osmosis systems for a whole-house solution that are on the market, customer feedback is extremely limited.

This one works on a very similar principle. It can still remove chlorine, VOCs, chemicals, and radon from your water supply, as well as nasty odors, colors, tastes, and cloudiness. On the plus side, it doesn’t remove all minerals like calcium and magnesium.

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

6. APEC Water Systems RO-90 Ultimate Series

Best Reverse Osmosis System for Hard Water

If you want a homegrown product, this one from APEC is engineered, designed, and assembled in the USA. It’s FDA-certified as having food-grade tubing and has a 100 percent lead-free faucet.

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

Apec claims that this system is fully automated and can effectively remove contaminants from homes with very hard water or variable water pressure.

What We Like

Large Filters

The filters on this system have a high capacity and are larger than some other under sink reverse osmosis systems. This means they won’t need changing 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 block to remove chlorine, bad tastes, and smells. These also remove commonly found chemicals and VOCs.

The fourth stage has a membrane from Dow, which we’re told is the industry’s leader in high-quality innovation. It could remove 99 percent of the total dissolved solids from your water. These include chromium, lead, fluoride, bacteria, radium, viruses, and lead (5).


The company has confidence in its product and offers you peace of mind with its two-year warranty. It also provides lifetime technical support.

What We Don't Like

Takes Up More Room

While the larger filters on this system have some benefits, they also have some setbacks. This system measures 11 inches by 11 inches by 15 inches and will take up more room under your sink.

Difficult Installation

This could be a product that you need a plumber’s help with. Many find the installation process difficult, although 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

7. Brondell RO Circle Water Saving Filter System

Best Compact Reverse Osmosis System

If you’re pushed for 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 could fit comfortably into a corner of the under sink cupboard.

It comes supplied with a beautiful chrome faucet that has an LED filter change light. This is great as you’ll be alerted when it’s time to replace your filters.

What We Like

Water-Saving Technology

Brondell advises us that its patented technology in this unit wastes less water than some other conventional reverse osmosis systems. The company claims its circle system eliminates back pressure, resulting in a water loss ratio of 2:1.

It’s also included a proprietary smart valve and flexible water tank that brings increased efficiency in delivering you filtered water.

Auto Filter-Flushing

The membrane filter in the reverse osmosis section of this system flushes automatically. This is designed to extend the life of the filter and to prevent sediment from building up.

Quick Tank Refill

The tank in this system is smaller than a lot of others at 1.58 gallons. The good news is this should recharge in about an hour.


The Water Quality Association (WQA) has certified this system with its gold seal award for performance you can trust. It also meets certified standards set by the NSF and ANSI.

What We Don't Like

Slow Faucet Flow

While many love the taste of this water, they’re disappointed with the slow flow of water from the faucet.

Small Storage Tank

The water storage tank on this unit is small, and many wish it was larger. That being said, it can take between 40 minutes to an hour to recharge so you can time it for low-demand periods.

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

8. Reverse Osmosis Revolution Portable Portable 5-Stage RO System

Best Portable Reverse Osmosis System

Are you looking for a reverse osmosis system for your RV or camper? Maybe you want one you can move from your faucet to your washing machine, to your bathroom, or to filter water for your garden.

This countertop version from Reverse Osmosis Revolution comes with an adapter to fit most faucets. However, there are eight adapters you can choose from; if you email the company, they’ll send you a different one.

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

What We Like

Five-Stage Filtration

All the filters for this system are 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 to filter the more common chemicals and VOCs. It also removes chlorine, nasty tastes and odors, and cloudiness.
  • Stage 3: The third stage is a TFC high-rejection reverse osmosis membrane to remove dissolved solids.
  • Stage 4: The fourth has a deionizing bed that can remove radiation,
  • Stage 5: The final stage is a coconut carbon to prevent any leftover sediment from getting through.

Long-Lasting Filters

The company claims that their filters should last eight to 12 months, or 1,000 gallons of water. This could mean less expense on filter changes.

Satisfaction Guarantee

Should you fit your system and decide you aren’t happy with it, the company offers a 14 day, 100 percent satisfaction money-back guarantee.

What We Don't Like

Slow Water Production

It appears the flow of filtered water through this unit can be slow. It could be worth using a water pitcher to collect your water ahead of time, so it’s 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

9. iSpring Commercial Grade Reverse Osmosis Water System

Best Commercial Reverse Osmosis System

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

The system doesn’t come with a tank, and with the high output level, you’re going to need quite a large one. iSpring does make a 20-gallon tank, or you could purchase a larger one like this 55 gallon one from Water Prepared.

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

What We Like

Oversized Filters

The pre-filters on this system measure 20 inches each and are good for about 30,000 gallons of water. There are also three reverse osmosis membranes that can process 100 gallons of water per day each. This means the filters won’t need to be changed frequently, even though they’re being used more.

Pump and Gauge

Included in the package are a pressure gauge and an automatic booster pump. These help you check the water pressure and make sure the pump is performing efficiently.

If the water pressure drops, it could be an indication that it’s time to change the reverse osmosis filters. We’re advised they should last between two to three years.

Free-Standing Frame

The entire system is seated in a supplied free-standing frame. This means everything is contained, and you should be able to find an appropriate place near your water source to stand it.

What We Don't Like

Not a Whole House System

Like many other reverse osmosis systems, this one is designed to fit one water source. Some have worked around this by getting a very large water storage tank to provide water to their homes. However, it seems you would need some plumbing know-how, or get a professional to do this for you.

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

10. PuricomUSA Countertop Reverse Osmosis Water Filter

Best Countertop Reverse Osmosis System

Another option for reverse osmosis filtered water is a self-contained countertop unit. This one from Puricom comes in a choice of silver-white or space-black to match your kitchen decor. There aren’t any hoses or faucet connections, and there’s no lost cupboard space with this one — plug it in, fill it with water, and off you go.

Measuring 9.5 inches by 14.5 inches by 16.25 inches, you need to find a space that it can fit into. The good thing is that it doesn’t need any clearance at the top or the sides — the water is loaded and dispensed from the front of the machine.

What We Like

Four-Filter System

There are four filters within this unit:

  • 1st: A five-micron sediment filter to remove larger particles like rust or dust.
  • 2nd: A coconut-based active carbon filter in block form. This helps remove pesticides, chlorine, and organic matter.
  • 3rd: Next comes the reverse osmosis membrane, which can produce 75 gallons of water per day. It helps remove remaining contaminants and heavy metals from the pre-filtered water.
  • 4th: Finally, the fourth stage filter returns magnesium and carbon to the water and helps improve the taste and mineral content.

Filter Change Alert

There’s a red light on the machine that notifies you when your filters need changing. A flashing red light means the pre and post-filters need replacement, which should be approximately every 12 months. A steady red light means the reverse osmosis membrane is expired, which should happen about every 24 months.

No Installation Required

You don’t need any plumbing knowledge to use this unit. It fills with water from your faucet and filters it into a half-gallon tank. The tank takes about 15 minutes to fill, and once it’s finished, it switches itself off.

What We Don't Like

Take Care Removing the Reservoir Tank

The waste water from this system drains back into the empty reservoir tank and then needs to be removed and disposed of. Some found that this can leak when removed and needed a towel under the unit 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

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. It’s a bit like a filter in your coffee machine that allows water (flavored with coffee) to pass through, but not the coffee grounds.

Under the normal process of osmosis, you would expect clean water to slowly move back to the side where the dirty water is (6). The “thinner” water would permeate the “thicker” water to gain equilibrium.

However, in reverse osmosis, the pressure of the incoming water or a pump forces the dirty water through the membrane, reversing the process of osmosis. The clean water that’s filtered is collected and comes through your faucet.

You might be wondering what happens to the water on the dirty side that’s now loaded with impurities. Eventually, it becomes hard to push water through the membrane, and the system drains this water away. Fresh water replaces it, and the process begins again (7).

Reverse osmosis systems can waste quite a lot of water as they generally drain the dirty water into the sewage system (8). The wastage from one of these systems can be between 20 and 30 percent of the incoming water. This can mean an increase in your water bills (9).

What Does an RO System Remove from Water?

RO systems consist of several filters that each remove contaminants from your water. The filter stages usually number between two and seven (10).

Stage 1

This is a prefilter stage and usually uses a membrane to remove large particles of contaminants such as stones, silt, rust, and clay. They won’t allow contaminants above a specific size to pass through, usually at 5 microns.

Stage 2

A carbon filter is usually used at this stage to remove things like 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 inserted into the system to remove even more particles from the water. This one uses a more dense and compact form of carbon to block even smaller particles.

This means, by the time the water reaches the reverse osmosis membrane, it’s already a lot cleaner. The two prefilters can also help your system last longer and work better, as chlorine and other contaminants could damage the reverse osmosis membrane.

Stage 4

This is the stage in the filtration process where reverse osmosis happens. The membrane in this stage can remove the smallest particles from your water. These can be anything larger than 0.001 microns and include things like heavy metals or radioactive contaminants.

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

Stage 5

Often the final step in many reverse osmosis systems, this one removes contaminants that can affect the taste and smell of your water. This could be chlorine, sulfur, viruses, and bacteria. It’s generally another carbon filter that’s finer than the first two.

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

Stage 6

All these stages of filtration remove contaminants from the water, but they also remove beneficial minerals. This stage aims to restore some of those minerals to the water to improve the taste and ensure you get minerals needed from drinking water. The type of minerals added could include calcium and magnesium, both essential for healthy bones and teeth (13).

This stage will also change the pH level of the resulting water. After 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 involves the use of an ultra-violet 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 fitted with this final stage will need a power source nearby to plug the unit into.

Additional Stages

Some manufacturers might state they have stages beyond the seventh one, but these generally don’t add any more to the process. They could be further filters to reintroduce minerals to the water.

What is Reverse Osmosis Water Used For?

Water that’s passed through a reverse osmosis system could have several uses (17).

Drinking Water

If you’re a fan of bottled water, a reverse osmosis system could be a good investment. Depending on where you live, the water quality that comes from your faucet could be less than desirable to drink. Filtered water from an RO system can give you contaminant-free water that tastes better and might be better for your health.


Impurities found in your municipal or well water supply contain things like chlorine, which could discolor or change the flavor of your food. Using pure water from a reverse osmosis system might improve your cakes, pasta, bread or soups — yummy!

Clear Ice Cubes

Have you ever noticed the bits that float around in your glass after you have added ice cubes to a drink? These could be impurities from your water. The purer water from a reverse osmosis system could give you clearer ice cubes — think how good they would look in a cocktail.

Washing the Car

As this water has had the minerals removed from it, it could give you a spot-free finish when used to wash your car.

Pros and Cons of Reverse Osmosis Systems

Consider the factors mentioned below before investing in an RO system.


  • No added salt: Many water softener systems used in the homes use salt as part of the process. This could be bad news if you’re on a low sodium diet for health reasons (18). Reverse osmosis filters means there’s no salt added during the process, so it could be a healthier choice.
  • Cleaner appliances: Using water from a reverse osmosis system in appliances like your coffee maker, could reduce the buildup of minerals. This is especially the case if you have a system that does not replace calcium and magnesium — two main culprits behind scaling (19). If you have a whole house system, your dishwasher, washing machine, showers, pipes and faucets could also be protected from scale.
  • More efficient soap products: The lower pH of reverse osmosis water means the hardness has been removed. This can allow your shampoos, soaps, detergents, and dishwashing liquids to work better (20).
  • Money-saving: Installing a reverse osmosis system could reduce your expenditure in a few ways: no need for bottled water, longer life expectancy for appliances, and more efficient soap products.


  • One faucet only: Reverse osmosis systems are designed to fit on one faucet in your home. This could be under a sink in your kitchen or bathroom or a countertop model.
  • Mineral removal: Although this doesn’t apply to all models, the majority of these systems filter out minerals that could be beneficial to your health. Some add certain ones back to water through a post-filter at the end of the process.

Types of Reverse Osmosis System

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

These systems are designed to fit into a cupboard under the sink in your home. They could have three or more filters and the reverse osmosis membrane. They’re generally supplied with a faucet for 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.


  • Takes up cupboard space.
  • Only provides filtered water from one faucet.

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

  • Attached to faucet: The first type is a combination of filters that have an attachment that fits your existing faucet. They tend to be smaller than the similar version that fits under your sink.
  • Standalone: The second type 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, the water tank for the conditioned water tends to be small.


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


  • Lower water output.
  • Need space on your counter.

Although there are products on the market for whole house reverse osmosis systems, they’re very expensive and have little or no customer feedback. A good alternative is a whole house filter unit.

They don’t have an RO membrane fitted. However, they do work on a similar principle, removing chemicals, chlorine, radon, and VOCs from your water supply. Also, they remove bad taste, odors, cloudiness, and discoloration.

One of the benefits of these systems is they don’t remove calcium and magnesium, so these and some other minerals remain in your water. Additionally, they treat the entirety of the home’s water supply, fitting onto your mains water supply.


  • Easy to install.
  • Easy filter change.
  • Don’t remove essential minerals.


  • Not strictly an RO system.
  • More expensive than other options.

These are the same as your countertop system. They can easily be moved from one faucet to another, taken with you when you travel or used in your RV or camper for holidays.

Just like the countertop ones, they can be a standalone option or fixed to a faucet.


  • Easy to install and remove.
  • Can be used when traveling.
  • Good for RVs and camper vans.
  • Can be moved to different faucets in the home.


  • Filter less water at a time.
  • Require more frequent filter changes.

How to Choose a Reverse Osmosis System

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

Water Flow

Check the water flow for the system you select. Make sure that it can supply enough water for you and your family’s needs. This is normally 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 the type. Check that the one you choose has the filters you would prefer. Some will work better for well water with high iron content, while others will remineralize your softened water.

You could always ask your water supplier for a quality report before choosing to make sure you’ve covered all the bases (21).

Another consideration when it comes to filters is the cost and frequency of change. These items do have a limited lifespan and will need changing out, some every three months or so, some annually.

Tank or Tankless

Decide whether you want a tank as well to store your water ready for use when you need it. Tanks come in different sizes, so make sure you select one that will hold enough for your needs.

A tankless system might be a good option if your demand for water isn’t high, or you don’t mind a slight delay when you want water.


Before purchasing your reverse osmosis system, decide where you’ll place it and if you have enough room for it. Some can be installed reasonably easily with the manufacturer’s directions.

Ask For Help

If you’re unsure about how to install your chosen system, you might need to employ a professional to do it for you.

Another thing to take into account is whether you have permission to fit a reverse osmosis system. If you rent, you might need to check with your landlord before fitting one to the water system. You could still invest in a countertop version if your request is denied.

Water Pressure

If you live in an area where the water pressure is less than adequate, you will need to select a reverse osmosis system that comes with a pump. Your water pressure, if it’s below about 40 psi, might not be enough to force the water through the membrane (22).

You can check with your water supplier what the pressure rate is for your home or invest in a pressure gauge and check it yourself.

Get Filtering

Having a reverse osmosis system means you will have filtered water “on tap” whenever you want it. Many of these systems come with everything you need to install them, and you should be able to do this by following the manufacturer’s instructions. Remember, if you’re unsure, call a professional to fit the system for you.

The system you choose depends on the size of your family and how much water you need. Combine this with the space you have available and there should be one to suit your needs within our recommended products.

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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.