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A specialized form of water filtration, a reverse osmosis system gives you purified water from the tap with a simple DIY set-up. Installing a reverse osmosis system can eliminate concern over the most common water contaminants and reducing dependency on plastic water bottles. These multiple-stage water filtration systems remove up to 99 percent of total dissolved solids (TDS) from your water supply, providing water that tastes fresh and is clean from contaminants.
While there are plenty of water filtration options on the market, a reverse osmosis system uses a specialized filter that is so fine virtually nothing but water molecules can squeeze through. Tankless RO systems filter water on-demand and have less water waste, while typical units hold purified water in a storage tank. When comparing options for a reverse osmosis system, check out the clean-to-waste water ratio, the size of the container or storage tank, and the speed of filtration to find a model that can meet your needs. Also consider whether you want a system with a re-mineralization filter, which adds back in beneficial amounts of calcium and magnesium.
Consider these top reverse osmosis systems for fresh, filtered water.
Best Overall: APEC ROES-50 Reverse Osmosis System
Number of Stages: 5 | Filtration Method: Multi-method | Included Filters: 5 | Remineralization: No
Includes faucet dispenser
Automatic water shutoff
Five stages of filtration
Undersized for large households
The APEC ROES-50 is a great option for improving tap water quality. This five-stage reverse osmosis system removes up to 99 percent of the most common contaminants found in tap water, including lead, chlorine, bacteria, copper, fluoride, and iron. The filtration system includes double carbon blocks for enhanced performance. Take note that there is no remineralization filter, so the water may taste "flat" compared to untreated drinking water.
This reverse osmosis system is most often used under kitchen sinks to provide filtered water for drinking and cooking. The output is 50 GPD, which is suitable for average household needs of three to four people. The APEC ROES-50 includes a 4-gallon storage tank, faucet dispenser, along with the filter set, necessary tubing, and an installation kit. Filter life is six to 12 months for stage one to three filters, and two to four years for the reverse osmosis membrane and carbon filter.
Best Tankless: Waterdrop D6 RO Water Filtration System
Number of Stages: 5 | Filtration Method: Carbon | Included Filters: 1 | Remineralization: No
Single cartridge with annual replacement
Reduced water waste
Not suitable for well water
A tankless reverse osmosis system saves space under the sink, produces less waste water, and increases the system’s capacity to produce purified water. The Waterdrop D6 RO Water Filtration System is a great option if you’re looking to do all of that and enjoy easy maintenance of the system. Plus, it includes a smart faucet dispenser that provides real-time insights on water quality based on TDS.
This option for a tankless reverse osmosis system measures about 16 x 6 x 12 inches, leaving room under most sinks for cleaning supplies and storage. It installs in less than 30 minutes according to the manufacturer and annual filter changes are super simple, thanks to the design of the five-in-one composite filter. Rated for 600 GPD, the Waterdrop D6 supplies even large families with fresh, purified water. It also does so with less water waste; the ratio is 1.5:1 for purified water to waste water.
Best Under Sink: Home Master Artesian Full Contact Reverse Osmosis Water Filtration System with Permeate Pump TMAFC-ERP
Number of Stages: 7 | Filtration Method: Multi-Method | Included Filters: 4 | Remineralization: Yes
Has a re-mineralization filter
Easy filter changes
No housing for filters and water lines
Under sink reverse osmosis systems are the most popular type, since the majority of the system—filter housing, storage tank, and plumbing tubes—is tucked away and out of view. Since purified water that has been stripped of natural minerals is stored in the holding tank, the slightly acidic water can cause holding tank degradation over time. However, the Home Master Artesian Reverse Osmosis System solves this dilemma by using a full contact system. This type of reverse osmosis system adds beneficial minerals to the water twice—once before it enters storage tank to avoid tank degradation and once before dispensing to ensure excellent taste and proper pH.
Another notable feature of this under sink reverse osmosis system is Home Master’s easy-change filter cartridges. The canister and filter media are integrated into a single unit that you replace when its time for a filter change. This means no tools are needed and you’ll never worry about the filter housing cracking or becoming a breeding ground for bacteria. The trade-off is that a lack of housing means the modular filters and tubes are exposed under the sink, rather than being tucked into a sleek housing unit like some other under the sink reverse osmosis systems.
Best Countertop: AquaTru Countertop Water Filtration Purification System
Number of Stages: 4 | Filtration Method: Carbon | Included Filters: 3 | Remineralization: No
No plumbing required
Filter light alerts you when it’s time to replace
Limited 3-quart purified water tank
Must be plugged in for operation
For a reverse osmosis system with no plumbing or installation requirements, check out a countertop purification system. AquaTru is a popular choice for renters or if you want to purify water without taking up space under the sink. The 18 x 18 x 15 inch unit sits on the counter and plugs into a standard household outlet. There are three cartridges that house the sediment, carbon, and reverse osmosis filters. Filter life is expected to last for 600 to 1,200 gallons of purified water, so your replacement schedule will depend on frequency of filtration.
To use this countertop reverse osmosis system, you fill the tap water tank (1-gallon capacity), wait for the water to pass through all four stages of filtration, then dispense purified water from the clean water tank. For every 1 gallon of tap water, the AquaTrue produces about 3 liters of purified water. The entire process only takes a few minutes, so you can either leave the water in the dispensing tank or transfer it to a pitcher or other storage tank in the refrigerator.
Best with Remineralization: iSpring RCC7AK 6-Stage Under Sink Reverse Osmosis Water Filter System
Number of Stages: 6 | Filtration Method: Multi-Method | Included Filters: 6 | Remineralization: Yes
75 GPD output
Transparent sediment filter
Unremarkable waste water to clean water ratio (1:3)
Alkaline filter needs replacing every six months
Since a reverse osmosis membrane removes particles down to 0.0001 microns in size, purifying water in this way removes bacteria, sediment, VOCs, and other contaminants. However, it also removes minerals and alters the pH of the water. So if you’re looking for that familiar "hard water" taste, then choose a reverse osmosis system with a remineralization filter, like the highly-rated iSpring RCC7AK.
This is a six-stage filtration system, with the final step being an alkaline remineralization filter. Instead of the slightly acidic water that results from standard five-step reverse osmosis systems, the last stage of the iSpring RCC7AK. Filters for stages one through three, along with the alkalinity filter, will need to be changed about twice a year. The reverse osmosis membrane will last two to three years before needing replacement, and the post carbon filter needs replacement annually.
Best High End: Brio G20-U Reverse Osmosis Filtration System
Number of Stages: 5 | Filtration Method: Sediment, Carbon | Included Filters: 2 | Remineralization: No
Choose between filtered or purified water
Faucet dispenser provides water quality readings
Filter life indicator light
Filter your water two ways with this high-end reverse osmosis system from Brio. This slim, tankless RO filtration solution provides purified water for drinking or cooking, along with filtered water for general household tasks—like washing dishes. The result is longer filter life, since you’ll only treat water with advanced filtration methods when you want it. The included faucet dispenser features two handles; use one to send water through a general two-stage filter cartridge, and the other to start the flow of purified water through the more advanced five-stage reverse osmosis filter cartridge.
In addition, this advanced reverse osmosis system has an impressive 2:1 ratio of purified to waste water, especially when compared to some RO systems that produce 3 gallons of waste water for every 1 gallon of purified water. While the Brio Reverse Osmosis Filtration System might feel like a splurge, the extra expense is minimized when you consider longer filter life, less water waste, and the savings you might see if you stop buying bottled water.
Best for Well Water: HomeMaster TMHP HydroPerfection Reverse Osmosis System
Number of Stages: 9 | Filtration Method: Multi-Method | Included Filters: 5 | Remineralization: Yes
UV light for sterilization
Advanced nine-stage filtration
Easy filter changes
No housing to hide filters, tubes
Well water presents additional water purification concerns, including eliminating the presence of microorganisms like coliform bacteria or eradicating heavy metals such as iron. For this reason, you’ll want to choose a reverse osmosis system with advanced stages of water filtration. We’d also recommend a model with a UV light, since it’s a proven method of destroying viruses, bacteria, and fungi.
The HomeMaster HydroPerfection is well-equipped as a reverse osmosis system for well water. It features nine stages of filtration, including reverse osmosis, sediment and catalytic carbon filtration. A UV light chamber sterilizes 99.99 percent of microorganisms and is the last step of the purification process. In addition, the system is equipped with a permeate pump which boosts clean water pressure and reduces waste water.
There are five filter cartridges to replace on an annual basis (or every 2,000 gallons), along with the UV bulb. Like other HomeMaster filtration cartridges, these are all-in-one units that don’t require you to open the housing or use any tools for replacement. Discard the old filter cartridge and insert a new one with minimal effort. There’s also no opportunity for biofilm or bacteria to build up inside the filter housing.
Best Budget: PureDrop 5-Stage Reverse Osmosis Water Filtration System with Pre-Filter Kit
Includes replacement pre-treatment filters
Removes up to 99 percent of TDS
Smaller capacity than competition
Number of Stages: 5 | Filtration Method: Carbon Block, Sediment | Included Filters: 8 | Remineralization: No
While many reverse osmosis systems cost a few hundred dollars, you can spend less and still have peace of mind about your drinking water quality with a budget system. The PureDrop RTW5 Five-Stage Reverse Osmosis System is easy on the wallet but tough on contaminants. This filtration system utilizes sediment and carbon filtration before squeezing water molecules through a fine reverse osmosis membrane for water with up to 99 percent of TDS removed.
Things you won’t see in a budget reverse osmosis system include a remineralization filter, digital readings of TDS, or a tankless system. The PureDrop RTW5 does take up substantial room under the sink with a 4-gallon holding tank. However, this affordable option includes a replacement set of pre-treatment filters, meaning you won’t need to open your wallet for a new set any time soon.
Our top choice is the APEC Water Systems Essence Drinking Water Filter System (view at Amazon) since it offers five stages of filtration and filters are long-lasting, easy to change, and widely available. If you're looking to spend less, consider the PureDrop Five-Stage Reverse Osmosis Water Filtration System (view at Lowe's). It's also a five-stage RO system but may require more frequent filter replacement.
What to Look for in a Reverse Osmosis Water Filter
Unlike traditional water filters, not all of the water that is pumped through a reverse osmosis filter comes out the other side as drinkable water. Only a relatively small percentage—50 percent or less—is filtered, and the rest is considered waste. When possible, avoid units with 75 percent or more waste, especially if you are treating a high volume of water per day. This unit is typically measured in ratio form, so a tank that produces 75 percent waste will have a filtered water to waste water ratio of 1:3.
Reverse osmosis filtering takes time, so most filters of this type have tanks that store water, rather than filtering it on demand. If your family drinks a lot of filtered water or you are filtering all of your tap water through reverse osmosis, make sure your tank is big enough to accommodate your needs.
While there are reverse osmosis filters that can filter water as you need it, most of them take some time to refill. If you are replacing your regular tap water with purified water, look for a unit that can filter 50 or more gallons a day (the unit measurement for this number is called GDP). If you're just using it for drinking water, you can opt for a unit with a slower refill rate and a smaller tank.
How does a reverse osmosis system work?
In every reverse osmosis system, there is an RO membrane, sediment filter, carbon filter, and several stages of filtration. When water first enters the system, it goes through prefiltration which usually consists of the sediment and carbon filter to remove sediment or chlorine that could clog up the membrane.
Water then goes through the membrane where dissolved particles are further removed. Once the filtering is complete, it goes to the system's storage tank where it is ready for use. When you turn on your faucet, the filtered water will come from the storage tank through another filter in the system that polishes it for drinking.
How do you install a reverse osmosis system
If you're installing a reverse osmosis system underneath your kitchen sink, you'll first want to make sure you have enough room in your cabinet for the storage tank and filters. It's best to install the sink spigot first so you're able to get the lines under the countertop before it gets crowded underneath the sink. Installation is simple and only requires basic plumbing knowledge. For detailed instructions with photos for reference, check out our full article on how to install a reverse osmosis system.
How do you replace filters in a reverse osmosis system?
Every reverse osmosis system requires periodic maintenance to keep your water as pure as possible. If you don't replace your filters and membrane every so often, you risk lowering the quality of your water and damaging or clogging the system. Refer to the owner's manual for how often to replace your filters, but this will also depend on the quality of the water in your area.
Although it doesn't require professional plumbing skills to change the filters yourself, you'll want to read the manufacturer's step-by-step instructions carefully on how to replace them. Make sure to purchase the right filters that need replacing as there are both carbon pre-filters and carbon post-filters for reverse osmosis systems.
Why Trust The Spruce?
This article was written by Erica Puisis, a freelance home writer who has been contributing to The Spruce since 2017. When researching picks for this list, she consulted dozens of customer and third-party reviews, considering RO systems with and without a storage tank. She evaluated the most popular options based on the water waste of each system, filtration speed, filter maintenance, and storage tank considerations. All of our recommendations include at least four stages of filtration and some include a remineralization filter.