Best Under Sink Reverse Osmosis System 2025? 13 Units Tested!

Under Sink Reverse Osmosis Systems

• Waterdrop G3P600
• Home Master TMHP-L HydroPerfection Loaded
• APEC ROES-50 Essence
• Brondell H2O+ Circle
• GE GXRQ18NBN
• Frizzlife PD600-TAM3

Please note: This page is still a work in progress. Additional content and details will be added shortly – stay tuned!

Paraphrased Video Script

In this video, we’re bringing you an updated comparison of the 11 most popular and most effective under sink ROs which, as before, includes professional and independent lab testing worth thousands of dollars conducted on all systems to learn more about their real-life contaminant reduction capabilities.

Hey, it’s Sara from BOS Water, today with an updated version of our big under sink reverse osmosis system comparison video. What’s changed? We’ve run additional tests, refined our rating process, and some things have shifted on the manufacturers’ side. Given all that, we now have a new RO system at the top of our list. Also, there are a few new aspects about our prior recommendations that we think are important to discuss. And finally, we’ve tweaked our opinion on RO remineralization.

But assuming that most of you didn’t watch our previous under sink RO comparison video, I first want to introduce the 11 systems we’ve tested one more time, and also explain how we tested and rated them. By the way, we didn’t re-run most of our tests — simply because the original data was solid and still holds up. So feel free to skip this chapter if you’re already familiar.

The 11 Under Sink ROs Tested

• The SimPure T1-400 ALK
• The Frizzlife PD600-TAM3
• The Waterdrop G3P600
• The Waterdrop X12
• These 4 systems are tankless
• And then we have 7 tank-based models:
  • The APEC ROES-50 Essence
  • The Aquasana SmartFlow
  • The Brondell H2O+ Circle
  • The GE GXRQ18NBN
  • The US Water Systems All American RO
  • The Home Master TMHP-L
  • The Cloud RO

How We Tested and Rated

Most importantly, we wanted to determine real-life contaminant reduction capabilities. And we wanted to test if any of the systems might have a problem with leaching potentially harmful chemicals. And so we conducted our own lab testing, taking samples of our unfiltered tap water and samples of our tap water after it had been processed by each of the 11 systems.

We sent all samples to a professional and independent lab for analysis and studied the reports as they came back. This allowed us to compare the concentrations of all the different impurities and contaminants in our tap water before and after filtration.

Of course, for better comparability between the filters we followed a strict protocol taking each water sample. Most importantly, we wanted all ROs to be in perfect condition when sampling, so they were brand-new. All we did was install and prime following the provided manufacturer instructions. And because we felt that, due to how they work, installing these systems in parallel would make our lab results less reliable, we hooked up and sampled one unit after the other, taking an unfiltered and a filtered water sample each.

Still, please don’t consider our before vs after lab testing an exact science because the results can never be 100% accurate for several reasons such as natural fluctuations in water quality and testing interferences. Also, we can only test for the contaminants actually present in our water and at their respective concentrations. And finally and again for better comparability, our tank-based ROs were tested with their tanks shut off, so under ideal conditions. In other words, everyday performance might differ slightly. That said, under sink ROs are quite complex anyway and their general performance depends a lot on external conditions such as feed water quality and pressure (we tested at 75 psi), and how you actually use a system. So please keep that in mind for all our test data.

Aside from our lab testing, we checked each system for official NSF certifications for contaminant reduction. These certifications are independent of the water filter companies themselves and can be awarded by the NSF itself but also the WQA and the IAPMO – all 3 organizations are ANSI-accredited to do that.

We also checked each under sink RO for any additional contaminant reduction test data which can be valuable but needs to be taken with a grain of salt because sometimes contaminant reduction is not tested for the full filter life, or there might be other issues.

We also looked at the filtration process of each under sink RO, so the different filter stages, media, and methods used.

And, of course, we did a taste and odor test of the freshly filtered water.

For usability, we set up, used, and maintained each system following the provided instructions, taking notes on what we liked and didn’t like.

In addition, we performed several more tests:

• A dispensing speed test
• A filling speed test for our tank-based systems – plus we measured how much usable water we’d get
• A wastewater test where we measured how much of the input water we could actually use and how much went down the drain

Last but not least, our rating process is also based on:

• Initial price tag and long-term cost for replacement filters
• Overall system quality
• Product warranties
• Made in USA or not
• Frequent complaints from third-party customers
• Any additional features

Recommendations Overview

• First, our new top pick — the under sink RO that earned the highest overall rating among all 11 systems. Spoiler: it’s tank-based.
• Then our two favorite tankless units.
• And finally, a few more systems including the one with the highest filtration score, two Made-in-USA options, and one budget pick.

You can check our full analysis of each of our 11 under sink ROs including all lab reports in our Google sheet, linked in the description. The sheet also contains our product links and discount codes.

Please also consider subscribing to our channel and liking this video.

Alright so, our new under sink RO top pick based on the best overall rating is… the Cloud RO!

Cloud RO – Our New Top Pick

What does the Cloud RO have to offer — and how did it end up as our new top pick with the best overall rating when we completely skipped it in our first video? Let’s break it down starting with our lab testing:

• Removed most undesirable impurities and contaminants to 100%: chlorine, 4 disinfection byproducts, copper, barium, strontium, uranium
• Boron: 33% reduction, meaning most other under sink ROs performed better
• Nitrate: 72–99% reduction (small traces remained but too low to quantify, 6 other systems did slightly better)
• Fluoride: 80–99% reduction (small traces remained but unquantifiable, as good as other systems)
• Silver detected at 0.01 ppm, likely from remineralization cartridge — 10x below strictest health guideline, not concerning
• Increase in zinc (0.41 ppm) and manganese (0.01 ppm), assumed to come from remineralization stage

Summary: The Cloud RO did really well in lab testing, though a couple of systems did slightly better on specific analytes.

Remineralization Results

Our remineralization results reflect the shortest possible contact time between water and media to ensure consistency across systems. Most of the 6 remineralization ROs including the Cloud didn’t reach the minimum recommended thresholds for magnesium, calcium, or overall alkalinity.

However, additional testing with TDS meters allowing longer contact showed higher mineral content under everyday use:

• After 1 hour of downtime, 2 cups averaged 50–55 TDS, enough to reach recommended threshold
• From the third cup onward, TDS returned to lab levels, consistent with saturation and cartridge contact time
• Longer downtime allows more minerals to dissolve, though results vary significantly by design and usage

Conclusion: Integrated remineralization helps, but adding minerals manually is more reliable if it’s a priority. Still, integrated cartridges are a nice bonus if not overpriced.

NSF Certifications

• Certified against NSF Standard 58 for TDS, showing 98% removal
• No other certifications yet, but Cloud says more are coming
• Additional NSF test data (not certifications) show high removal rates for chlorine, chloramine, lead, VOCs, forever chemicals, chromium 6, nitrate, and fluoride

Filtered water tasted and smelled perfectly clean.

Usability

The Cloud RO shines in usability. It uses a storage tank since its filtration process is slower.

Setup highlights:

1. Cut a hole in countertop, insert faucet, secure with washer and nut
2. Connect faucet tube
3. Turn off cold water, disconnect, install T-valve, reconnect, attach inlet tube
4. Drill drain pipe hole, install drain clamp
5. Connect tank tube and place tank under sink
6. Install base, connect tubing, seat filter magazine
7. Turn on cold water, open tea valve, open faucet to release air
8. Flush by filling and purging three tanks before use

Filter replacements:

• Remove top by pinching sides
• Rotate filter counterclockwise to remove, twist new one clockwise to lock
• Replace lid and return system

Everyday use:

• Faucet flow: 1 cup in 6 seconds, about average for tank-based systems
• Dispensed 2.2 gallons before slowing to trickle
• Tank refilled in just over 23 minutes, fastest in comparison

Cloud RO App

• Free Android/iOS app connects via Bluetooth
• Tracks TDS at 3 points: tap water, post-RO, post-remineralization
• TDS readings not live — only taken when inlet valve opens; most users trigger 2–3 readings per day
• Displays running averages of recent readings
• App also tracks water consumption, tank level, and battery state
• Battery lasts 2+ years, new battery included with each filter set, return label provided for recycling
• App uses water data to track filter status and replacement timing
• Includes regional water quality reports (based on zip code)
• Includes “alkaline” pH and “5 healthy minerals” tabs, but these are estimates only (Cloud system cannot actually measure pH or minerals)

Wastewater

Cloud RO has the lowest wastewater ratio of all tank-based ROs tested:

• 0.56 gallons wasted per gallon purified with tank off
• Around 1:1 with tank on, thanks to permeate pump and electronic shutoff
• Standard tank-based ROs often waste 3–5 gallons per gallon purified

Other Notes

• Clean design, simple but solid faucet available in 4 finishes
• Battery-powered, no power outlet required
• Filter replacements include a return label for recycling the battery

Costs

• Upfront: $599, minus $50 discount code = $550
• Higher than average tank-based system, but includes extra features and app
• Limited 1-year warranty and 1-year satisfaction guarantee
• Annual filter cost: $200, includes new battery; about average for tank-based ROs

Summary – Cloud RO

• Top performer among 11 under sink ROs tested
• Great lab results, backed by NSF 58 certification and additional NSF test data
• Integrated remineralization, though mineral content varies
• Perfect taste and odor
• Easy to install, prime, use, and maintain
• Fast faucet flow and lowest wastewater ratio among tank-based systems
• High build quality and clean design
• App provides detailed monitoring
• Reasonable upfront and annual filter costs

Waterdrop G3P600 and X12 – Tankless Picks

These are our two favorite tankless ROs, the same as in our first video. Both filter water on demand using an electric booster pump, giving you a continuous stream of purified water and reducing dependence on feed water pressure. They also save space under the sink.

The Waterdrop X12 is larger and considered Waterdrop’s flagship, filtering water extremely fast with a very high faucet flow rate. However, it’s considerably more expensive and may not fit everyone’s budget.

Filtration Results

Waterdrop G3P600:

• Removed most impurities and contaminants to 100%
• Boron: 33% reduction (same as Cloud)
• Strontium: 94% reduction (negligible difference compared to higher results)
• Fluoride and nitrate: only minimum reduction rates calculable, small traces remained but unquantifiable
• Tiny amount of iron detected at 0.02 ppm, far below health guidelines, not concerning

Waterdrop X12:

• Almost identical to G3P600 results
• Slightly better at boron reduction
• Slightly lower strontium reduction

Conclusion: Both achieved great overall results similar to Cloud RO. Water aesthetics (taste and odor) were perfect.

Remineralization and UV

• X12 includes remineralization, with performance likely better in everyday use than lab tests showed, depending on downtime and usage frequency
• X12 also features UV light to kill germs, but since it’s designed for tap water, the benefit may be minimal — still, it doesn’t hurt
• UV shuts off automatically when not needed to save energy

NSF Certifications

Waterdrop G3P600:

• Certified against NSF Standards 42, 53, 58
• Covers TDS, fluoride, cadmium, chromium 6, selenium, chlorine, PFOA, PFOS
• TDS reduction rate: 93.59% (slightly lower than Cloud’s 98%)
• Additional test data provided for VOCs and emerging contaminants

Waterdrop X12:

• Certified against NSF Standards 42 and 58
• Covers chlorine and TDS only
• TDS reduction rate: 94.6% (slightly higher than G3P600, but still below Cloud)
• Additional Waterdrop test data covers all key contaminant types

Setup

Installation is straightforward and similar for both. Example (G3P600):

1. Turn off cold water supply, disconnect line, install feed water adapter, reconnect line
2. Install faucet: feed tubes through hole, secure with washer and nut underneath
3. Drill drain pipe hole, install drain saddle (ours was slightly too large, fixed with foam board)
4. Place RO system under sink, connect color-coded tubing
5. Connect faucet power cord and power adapter
6. Install filters with twist motion
7. Turn on water supply and power
8. System flushes for 5 minutes, then run faucet for 30 minutes to prime filters

For X12, the system flushes automatically for 30 minutes after assembly. Note: our unit leaked until we re-installed the pre-installed filters.

Usability

Waterdrop G3P600:

• Activate by opening faucet, booster pump starts filtration
• Speed test: 1 cup in 7 seconds
• Accurate TDS display on both faucet and module
• Filter life indicators provided

Waterdrop X12:

• Dispenses extremely fast: 1 cup in 4.25 seconds
• Touch controls allow selection of 5–64 ounces or continuous dispense
• Continuous mode can be stopped anytime
• “Faucet Mode” prevents splashing but disables refrigerator/ice maker connection
• Energy-saving mode reduces noise, though pump noise wasn’t bothersome
• TDS display and filter life indicators on faucet

Filter replacements are simple: one twist to remove and replace cartridges.

Wastewater and Auto-Flushing

Both systems performed well in wastewater tests:

• G3P600: 0.75 gallons wasted per gallon purified
• X12: 0.5 gallons wasted per gallon purified

However, both include automatic flushing cycles to counter TDS creep and scaling:

• G3P600: flushes after 5 minutes of non-use, wasting about 4.5 cups each cycle
• X12: flushes after 10 minutes of non-use, wasting about 6 cups each cycle

This raises total wastewater if only small amounts are dispensed:

• 1 cup from G3P600: total ratio about 1:5.25
• 1 cup from X12: total ratio about 1:6.5

To improve efficiency, dispense larger amounts:

• Dispensing 1 gallon from G3P600: 1.02 gallons wasted
• Dispensing 1 gallon from X12: 0.9 gallons wasted
• Dispensing half a gallon: ratios about 1:1.2 to 1:1.3

The X12 allows disabling auto-flushing, but this risks membrane scaling and TDS creep.

Costs

Waterdrop G3P600:

• Upfront: $539, often discounted; additional 5% off with exclusive code
• Warranty: 1 year
• Annual filters: about $145, with 5% subscription savings

Waterdrop X12:

• Upfront: $1,299 list, usually $1,000–$1,100 with discounts and code
• Warranty: 2 years
• Annual filters: about $175, with 5% subscription savings

Summary – Waterdrop G3P600 and X12

• Best tankless under sink ROs tested
• Great lab results, similar to Cloud RO
• NSF certifications stronger for G3P600 than X12
• Perfect taste and odor
• Very fast filtration, especially X12
• High build quality, easy installation, easy maintenance
• Wastewater efficiency depends on dispensing larger amounts due to auto-flushing
• G3P600 is affordable, X12 is premium-priced

Aquasana SmartFlow

• Achieved the best results in lab testing
• Has all relevant NSF certifications
• Filtered water was flawless, earning the highest overall filtration score
• Includes remineralization
• Build quality feels lower than other systems
• Plastic valve on storage tank feels fragile
• Faucet base leaked slightly, couldn’t be fixed
• Some tubing too short, making installation difficult
• Upside: filters easy to prime, system easy to use afterward
• Speed test: 1 cup in 5.25 seconds
• Filter replacements simple, but no filter life indicator
• Additional tests: 1.81 gallons per tank, 43 minutes to fill, wastewater ratio 1:0.875 tank off, ~1:2.65 with tank on (according to performance sheet)
• Customer complaints: slow flow, leaking
• Upfront cost: ~$214.99 with discount or subscription
• Warranty: 2 years, plus 90-day satisfaction guarantee
• Annual filter costs: ~$360 (high), 15% discount available with subscription

US Water Systems All American RO and Home Master TMHP-L

Both of these are good options if you prefer Made in USA systems, though storage tanks are imported, and Home Master’s UV module is also non-US made.

US Water Systems All American RO:

• Strong lab test results, slightly better than Cloud and Waterdrop in some areas
• Great taste and odor
• No NSF certifications or other official test data
• Easy setup, priming, and use
• Second fastest faucet flow: 1 cup in 4 seconds
• Filter replacements simple but use traditional sumps
• Our package was missing the tank stand
• Tank test: ~2 gallons, took nearly 1 hour to fill
• Worst wastewater ratio: ~3.25 gallons wasted per gallon purified with tank off, 2–3 times more with tank on
• Build feels sturdy, features double O-rings on pre-filters
• Upfront: ~$600, with 5% discount code available
• Warranty: 5 years
• Annual filter costs: ~$95–185, 10% discount with subscription

Home Master TMHP-L:

• Strong lab results, great taste and odor
• No NSF certifications or other test data
• Setup a bit confusing for first-timers, instructions lacking
• Drain saddle wrong size, required replacement
• Other small installation issues
• Fastest faucet flow tested: 1 cup in 3 seconds, thanks to permeate pump
• Tank test: 3 gallons, 46 minutes to fill
• Wastewater ratio: 1.25 gallons wasted per gallon purified with tank off; permeate pump likely keeps it low even with tank on
• Remineralizes twice (before and after tank), which may increase mineral content and protect storage tank
• Includes cold UV module for sterilization, not tested
• Some customer complaints about faucet connections
• Upfront: ~$500, more affordable than All American
• Warranty: 5 years
• Annual filter costs: ~$140–150

APEC ROES-50 Essence

• Most affordable under sink RO tested
• Upfront: as low as $200
• Performed really well in lab testing
• Filtered water perfect in aesthetics
• Certified for NSF 58 (TDS reduction), but no performance sheet available
• Setup great overall, but our feed water valve leaked (likely missing gasket)
• Leaks also common complaint in third-party reviews
• Uses traditional filter sumps
• Fast faucet flow: 1 cup in 4.5 seconds
• Usable water: 3 gallons per tank, refill took 1 hour 24 minutes (slowest tested)
• Wastewater ratio: 2.31 gallons wasted per gallon purified with tank off, typical rates with tank on
• Good overall build quality
• Filters are standard-sized, off-brand replacements possible but not necessary
• Annual filter costs: ~$40–80, very low
• No filter life indicator

Final Notes

You can check our full analysis of all 11 under sink reverse osmosis systems, including lab reports, in our Google sheet. Also check the sheet and description box for product links and discount codes.

We also have a comparison of 10 countertop ROs and many other videos on our channel. Please consider subscribing and liking this video to support our work.

Feel free to ask questions in the comments, share your experience with these or other under sink ROs, or suggest which filters you’d like us to review next.

Thanks so much for watching — see you in the next one!