Best Reverse Osmosis Systems for Home (2026): 6 Under-Sink Picks

The short answer: Our top pick is the Brondell Circle (~$450). It is certified to reduce lead, arsenic (V) and fluoride, it needs no electricity, and our founder has used one at home for over four years. Want a faster tankless unit? Choose the Waterdrop G3P600 (~$539). On a budget, the APEC RO-90 (~$220) carries similar certified claims. If your water has nitrate, the Aquasana SmartFlow is the only pick here certified for it, but it was out of stock at Aquasana in every finish when we checked on November 8, 2026.

Reverse osmosis (RO) is the right tool for dissolved contaminants such as lead, arsenic, fluoride and nitrate. Before you buy, test your water so you know what you need to remove. Then check that the system's certification lists that contaminant by name. A system certified only for total dissolved solids (TDS) has not been certified to reduce lead or arsenic. Every arsenic certification here covers arsenic (V); if your test shows arsenic (III), common in well water, it must be converted to arsenic (V) first, so ask your lab.

Need a unit with no plumbing, for a rental or a small kitchen? See our best countertop reverse osmosis systems. If fluoride is your main concern, see our best fluoride water filters.

Brondell Circle Overview

The Brondell Circle is a compact under-sink RO system that runs with no electricity. Instead of a pump, it uses a patented smart valve and a flexible built-in reservoir. That reservoir holds 1.6 gallons, so it is not truly tankless, but it takes far less space than a separate tank.

WQA certifies it to NSF/ANSI 42, 53, 58 and 372. In its certified test, it cut lead by 98.1%, arsenic (V) by 99.8% and fluoride by 83.8%, according to Brondell's performance data sheet. It is also certified for cysts, VOCs, radium and TDS. It is not certified for nitrate, and Brondell says not to use it on water that is microbiologically unsafe.

Its certified daily production is 40 gallons, enough for most households' drinking and cooking. Its 33.5% efficiency rating means about 2 gallons go to the drain per gallon of drinking water. Brondell says it wastes up to 10 times less water than traditional RO systems when the reservoir is nearly full.

• Price: ~$450
• Filters: pre-filter set every 6 months (the faucet light flashes at 6 months or 475 gallons); RO membrane every 24 months
• Certification: WQA, NSF/ANSI 42, 53, 58 and 372 (WQA listing)

The Brondell Circle fits in a back corner under the sink

The replaceable cartridges sit behind the front cover

Our Hands-On Experience

Hands-on tested: our founder, Jeremiah Zac, has used this unit at home for over four years.

I've had my Brondell RO for over four years, and it's been used entirely for drinking and food prep. I also have a Berkey and some pitcher filters in the kitchen, so it isn't my only source of clean water. But for filling a pot for soup, washing vegetables or a quick glass of water, the Brondell is my go-to.

Installation. Installation was easy. It takes up about the space of a desktop computer and sits in the back corner under the sink. The color-coded lines make it easy to tell the inlet, outlet and drain lines apart. I added the provided T-valve to the cold-water line and drilled a small hole in the drain pipe for the drain line. The outlet connects to a chrome faucet next to the main kitchen faucet.

Water quality. The water tastes great. With a TDS meter, my filtered water reads 21 to 29 ppm when the filters are new, compared with about 390 ppm from the tap. That drop shows the membrane is working. TDS is not a safety test, though: it can't tell you whether lead, arsenic or bacteria are present.

Maintenance. The LED light on the faucet reminds me when a cartridge is due. Each swap is easy: remove the front cover and twist out the filter. I haven't always swapped on schedule; Brondell recommends new pre-filters every 6 months and a new membrane every 24 months.

Pros

No electricity or pump noise. Certified for lead, arsenic (V) and fluoride. Compact, with quick twist-off filters and a faucet light that tracks filter life.

Cons

Only a 1-year warranty. At 40 GPD it is slower than tankless units. It is not certified for nitrate or PFOA/PFOS.

Is it for you?

Choose the Brondell Circle if you want certified lead, arsenic (V) and fluoride reduction in a compact unit with no pump. The 1.6-gallon reservoir can run low if you fill a big pot, so it suits households that drink and cook with a few gallons a day.

Waterdrop G3P600 Overview

The Waterdrop G3P600 is a tankless RO system with a built-in pump. It makes filtered water on demand, so there is no tank to wait on. Waterdrop rates it at 600 gallons per day with a 2:1 pure-to-drain ratio. The original Waterdrop G3 is no longer sold.

IAPMO certifies it to NSF/ANSI 58 for TDS, fluoride, lead, cadmium, barium and radium (IAPMO listing), and to NSF/ANSI 53 for PFOA/PFOS (IAPMO listing). Its data sheet reports 88.23% fluoride reduction (Waterdrop data sheet). It is not certified for arsenic, nitrate or microbes, so choose a different pick if those are your concern.

The pump needs a power outlet under the sink. Waterdrop puts the average annual filter cost at about $145. If you want more output, the Waterdrop G3P800 (~$849 to $999) is rated at 800 GPD and holds the same certified claims.

Pros

Fast, on-demand water with no tank. Low waste for an RO system. Certified lead, fluoride and PFOA/PFOS reduction.

Cons

Needs an outlet. Not certified for arsenic or nitrate. The pump makes some noise while it runs.

Is it for you?

Choose the G3P600 for fast tankless water and certified lead and fluoride reduction on city water. Skip it if arsenic or nitrate is your main concern.

Cloud RO Overview

The Cloud RO is a tank-based RO system with an app that tracks water quality and filter life. It runs on batteries, so it needs no outlet. Its maker data sheet lists a 54% efficiency rating, the highest published rating among our tank picks, at about 0.9 gallon to the drain per gallon of drinking water.

Read its certification closely. NSF certifies the Cloud RO to NSF/ANSI 58 for TDS reduction only, at 42 gallons per day (NSF listing). Cloud also publishes lab results for lead, fluoride, arsenic, nitrate and PFOA/PFOS, but no certifier lists those claims. It costs about $599, and Cloud estimates $200 to $250 a year for filters.

Pros

The highest published efficiency rating of our tank picks (54%). No outlet needed. App tracking, remineralized water and a 5-year warranty.

Cons

The highest price here. Certified for TDS only, so its lead and arsenic figures are maker lab tests.

Is it for you?

Choose the Cloud RO if low water waste and app tracking matter most, and your water has no specific health contaminant you need certified proof for.

➔ Check price at Cloud

APEC RO-90 Overview

The APEC RO-90 is a classic 5-stage tank system: a sediment filter, two carbon pre-filters, the RO membrane and a carbon polishing filter. It runs on water pressure alone. At about $220 on Amazon, it is the lowest-priced certified pick here.

WQA certifies it to NSF/ANSI 58 for lead, arsenic (V) up to 300 ppb, fluoride, cadmium, copper, chromium, radium, selenium, barium and TDS (WQA listing). That claim list matches systems that cost far more. No published efficiency rating turned up in APEC's manual or listings. Its basic sibling, the ROES-50, is certified for TDS only, so check the model before you buy.

Pros

Low price with broad certified claims, including arsenic (V) up to 300 ppb. Standard-size filters. No power needed.

Cons

A bulky tank and five housings under the sink. No published efficiency rating. Only a 1-year warranty.

Is it for you?

Choose the APEC RO-90 if you want certified lead and arsenic (V) reduction at the lowest price and have room for a tank.

➔ Check price on Amazon

Aquasana SmartFlow Overview

Availability: out of stock at Aquasana in all five finishes when we checked on November 8, 2026.

The Aquasana SmartFlow replaced Aquasana's OptimH2O, which Aquasana no longer sells. It pairs a carbon pre-filter and RO membrane with Aquasana's Claryum stage and a remineralizer that adds minerals back for taste.

It is the only pick certified for nitrate. WQA certifies it to NSF/ANSI 42, 53, 58 and 401 for lead, arsenic (V), fluoride, nitrate, mercury and PFOA/PFOS (WQA NSF/ANSI 58 listing; NSF/ANSI 53 listing). In its certified tests, it cut fluoride by 90%, according to Aquasana's performance data sheet. It cut nitrate by 78% and PFOA/PFOS by 99.7% in the same tests (Aquasana data sheet).

The trade-off is output and waste. It makes 25.7 gallons a day with a 27.4% efficiency rating. At today's prices, its filters run about $310 a year.

Pros

The only pick certified for nitrate. Also certified for PFOA/PFOS, lead and arsenic (V). Remineralized water. Live phone support.

Cons

Low daily output. Higher yearly filter cost than most picks here.

Is it for you?

Choose the SmartFlow if your water test shows nitrate or PFOA/PFOS, or several contaminants at once.

Moen F9900 Overview

The Moen 4-Stage RO (F9900) is a tank system sold by SpringWell. IAPMO certifies it to NSF/ANSI 58 for arsenic (V) at up to 300 ppb, along with lead, fluoride, barium, cadmium, chromium, copper, selenium and TDS (IAPMO listing). That 300 ppb arsenic test level is the highest among our picks, tied with the APEC RO-90. IAPMO also certifies it to NSF/ANSI 53 for PFOA/PFOS, lead, mercury, VOCs, cysts, asbestos, MTBE and turbidity (IAPMO listing).

Moen's install guide also lists a separate NSF P231 certification for bacteria, viruses and cysts (Moen guide). Even so, Moen says not to use it on microbiologically unsafe water without adequate disinfection, so treat a contaminated well first. Moen backs it with a limited lifetime warranty while the original buyer owns the home. Moen's RO-compatible Sip faucet is sold separately.

It costs about $364 and makes 27.5 gallons a day. At SpringWell's prices, its filters run about $419 a year.

Pros

Certified for arsenic (V) up to 300 ppb, lead and PFOA/PFOS. Limited lifetime warranty for homeowners. No power needed.

Cons

Low daily output. The highest yearly filter cost here. The matching faucet costs extra.

Is it for you?

Choose the Moen F9900 if your arsenic (V) is high (it is certified up to 300 ppb) and you want Moen's limited lifetime warranty. If your arsenic test shows arsenic (III), ask your lab or dealer about oxidizing it first, since the certification covers arsenic (V).

What Is Reverse Osmosis?

Reverse osmosis is a process that uses water pressure to push water through a semi-permeable membrane. The membrane lets water through but holds back most dissolved salts, metals and other contaminants. The rejected contaminants are rinsed to the drain.

RO does not make pure H2O. The Brondell and Aquasana systems cut TDS by about 96% to 97% in certified tests, according to the Aquasana and Brondell data sheets. Home systems also pair the membrane with carbon filters, which handle chlorine and many chemicals.

Most home RO systems have three parts: pre-treatment, the RO membrane and post-treatment. Here is what each stage does.

• Sediment filter: traps sand, rust and silt to protect the later stages.
• Carbon pre-filter: removes chlorine, which damages RO membranes, and reduces many chemicals and odors.
• RO membrane: reduces dissolved solids, metals, fluoride and other dissolved contaminants.
• Storage tank: holds filtered water in tank systems so it's ready at the faucet.
• Post-carbon filter: polishes taste just before the faucet.
• Remineralizer (optional): adds calcium and magnesium back for taste. The Aquasana SmartFlow and Cloud RO include one.

Certified RO systems reduce a wide range of dissolved contaminants, but the numbers vary by system and by contaminant. These are the ranges from the certified data sheets of our picks.

RO is not a disinfection method. Use only microbiologically safe water, as Brondell and other makers state. For a well, test for bacteria first (CDC).

Beyond the filters, a home RO system has a few other parts worth knowing.

• Faucet: a separate drinking-water faucet mounts next to your sink. Some, like Waterdrop's, show TDS.
• Drain saddle: a clamp that sends rinse water into your sink drain.
• Pump (some models): tankless units use an electric pump. Some tank systems add a permeate pump or booster pump to cut waste or raise pressure.
• Filter-life indicator: a light or app that tells you when to change filters.

RO Water: Minerals, TDS and Common Myths

The main downside of RO water is that it also removes calcium and magnesium. WHO notes that food supplies most of these minerals, but it has also flagged long-term drinking of low-mineral water as a concern (WHO). A remineralization stage adds some back and improves taste.

Low TDS is not a safety test. EPA's TDS guideline of 500 mg/L is for taste and scaling, not health (EPA). A low TDS reading can't rule out lead, arsenic or bacteria, so check the certification for the contaminants you care about.

RO handles several contaminants that simpler filters can't.

• PFAS: EPA lists high-pressure membranes such as RO among the treatments found to remove PFAS, typically more than 90 percent (EPA). The Aquasana SmartFlow, Waterdrop G3P600 and Moen F9900 are certified for PFOA/PFOS. See how to avoid forever chemicals.
• Lead and arsenic: the Brondell Circle, APEC RO-90, Aquasana SmartFlow and Moen F9900 are all certified for lead and arsenic (V). Arsenic (III) must be converted to arsenic (V) first; ask your lab which form you have.
• Nitrate: high nitrate can make babies under six months seriously ill (EPA). Only the Aquasana SmartFlow is certified for it here, reducing nitrate/nitrite by 78% on average in its certified test (Aquasana). If you make infant formula, retest the filtered water before you rely on it.
• Microplastics: see our best water filters for microplastics.

How much water does reverse osmosis waste?

It depends on the system's efficiency rating. Among picks with a published rating, waste runs from about 0.9 gallon to the drain per gallon of drinking water (Cloud RO) to about 2.6 gallons (Aquasana SmartFlow). Waterdrop rates the tankless G3P600 at 2:1 pure to drain, about 0.5 gallon, but that is a maker figure, not a certified efficiency rating. Basic tank systems can waste 7 gallons or more.

Is there a downside to drinking reverse osmosis water?

RO water has fewer minerals, so it can taste flat. Most of your calcium and magnesium come from food, but a remineralization stage adds some back. RO also wastes water and needs regular filter changes.

Is there something better than reverse osmosis?

For dissolved contaminants like lead, arsenic, fluoride and nitrate, RO and distillation are the only common home options that handle all four; ion-exchange and adsorptive filters treat some of them. For chlorine and taste alone, a certified carbon filter is simpler and keeps minerals. See our best water distillers.

How much does a reverse osmosis system cost?

Our picks cost about $220 to $599, plus roughly $70 to $419 a year in filters at current prices. Professional installation adds to that if you don't do it yourself.

Do RO systems need electricity?

Tank systems usually don't; they run on water pressure. Tankless systems like the Waterdrop G3P600 need an outlet for their pump. The Brondell Circle needs none, and the Cloud RO runs on batteries.

How long does an RO system last?

The housing can last many years with regular filter changes. Membranes last 1 to 2 years on most of our picks' schedules (2 to 5 years for the APEC RO-90), and pre-filters 6 to 12 months.

The right system depends on what is in your water:

• Lead, arsenic (V) or fluoride in a compact unit: Brondell Circle (hands-on tested).
• Fast tankless water on city water: Waterdrop G3P600.
• Highest published efficiency rating (tank system): Cloud RO (certified for TDS only).
• Lowest price with certified lead and arsenic (V): APEC RO-90.
• Nitrate or PFOA/PFOS: Aquasana SmartFlow.
• High arsenic (V) and a long warranty: Moen F9900.

Key Takeaways

• Test first, then match the certification to the contaminants in your water.
• Read the listing: NSF/ANSI 58 always covers TDS, but lead, arsenic and nitrate are separate claims.
• Use certified numbers: certified daily output is often far below the membrane's GPD label.
• Brondell Circle is our top pick, and the one our founder uses at home.
• RO isn't for unsafe water: treat bacteria separately, especially on a well.

Comparing other filter types? See the best water filtration systems for home and the best countertop RO systems.