Best Under Sink Water Filter 2025? We Tested 21 Systems!

Under Sink Water Filters

• Waterdrop G3P600
• Epic Smart Shield
• Home Master TMHP-L HydroPerfection Loaded
• APEC ROES-50 Essence
• AO Smith AO-US-200
• Brondell H2O+ Circle
• GE GXRQ18NBN
• Frizzlife PD600-TAM3
• Culligan US-EZ-4
• Clearly Filtered 3-Stage
• Frizzlife SK99-NEW
• CuZn UC-200
• Aquasana Claryum 3-Stage Max Flow (AQ-5300+)

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

Paraphrased Video Script

Today we’re diving deep into 19 of the hottest under sink water filters on the market which we didn’t just install on our water supply – we spent thousands of dollars submitting unfiltered and filtered tap water samples for professional lab analysis. Ready to find out which under sink filters are the best and most effective under real-world conditions? Let’s go!

Hey, Sara here with BOS Water and our next big comparison, this time featuring 19 of the most popular and most effective under sink water filters! These are:

• The Clearly Filtered,
• And the CuZn UC-200 – both are inline systems so you can use them together with your existing kitchen faucet.
• The Frizzlife SK99-NEW,
• And the Epic Smart Shield can be used with a regular kitchen faucet or you upgrade to the optional dedicated faucet.
• And the Waterdrop TSU,
• The AO Smith AO-US-200,
• The Aquasana Claryum 3-Stage Max Flow a.k.a. Aquasana AQ-5300+,
• And the Culligan US-EZ-4 all come with their own faucets from the get-go.

So these 8 filters are “regular”, non-reverse osmosis, under sink filters. And in addition, we have 11 under sink reverse osmosis systems that were already part of our big under sink RO comparison video:

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

Regular Filters vs RO Systems

Generally, “regular” under sink water filters are less complex compared to RO systems, and so they tend to be more affordable. They also don’t waste any water which every home RO system does. Besides, pretty much no beneficial minerals will be removed during filtration. However, without an RO membrane, filtration is also less broad and less effective for certain types of impurities, especially those dissolved in water like many metals and salts.

What all 19 filters have in common is that they go under the sink for more countertop space, and you don’t need to look at them. The only visible part, depending on the model, will be the extra faucet. And by the way, we chose each under sink water filter based on popularity or because we thought it has promising specs. Also, we tried to cover the full price range from budget to premium.

Testing and Rating Process

We sent unfiltered and filtered water samples to a professional and independent lab for analysis, because we wanted to compare the concentrations of all the different impurities and contaminants in our tap water before and after filtration.

But before we could sample, we had to install and prime each filter. And because we wanted the systems to be in perfect condition when sampling, they were all brand-new and we followed the provided setup instructions to the T.

Aside from our own lab testing, we also checked each under sink filter for official NSF certifications for contaminant reduction and any additional test data the companies might provide.

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

Also for usability, we used and maintained each under sink filter as required. And in addition, we performed a few more tests:

• A filtration “slash” dispensing speed test
• A tank filling speed test for our tank-based RO systems – plus we measured how much usable water we’d get.
• And finally, for all under sink ROs we performed a wastewater test, so we measured how much of the input water we could actually use and how much went down the drain.

And last but not least, our rating process also takes all the other product aspects into account like overall quality and design, costs, warranties, frequent customer complaints, etc.

Our Top Recommendations

1. Our #1 pick: the filter which earned the highest overall rating among all 19. Spoiler alert: It’s a tank-based RO system.
2. Runner-up: our two favorite tankless ROs.
3. After that: the best regular under sink water filter which is also a great budget pick.
4. Finally: a few more options, both RO and non-RO, including the filter with the highest filtration score, 2 Made-in-USA products, and another budget pick.

But as usual, you can check our full analysis of all 19 under sink water filters including lab reports in this Google sheet linked in the video description, so everything is fully transparent. The sheet also contains our product links and discount codes, which I’ll also add to the description.

Cloud RO – Lab Testing

The best under sink water filter earning the highest overall rating in our comparison is the Cloud RO, a tank-based reverse osmosis system.

The Cloud could remove most undesirable impurities in our tap water to 100%: Chlorine, all 4 disinfection byproducts, copper, barium, strontium, and uranium.

• Boron was 33% reduced, nitrate between 72–99% reduced, and fluoride between 80–99% reduced.
• 8 other filters did slightly better for nitrate, and about half did better for boron.
• The Cloud may have released a trace of silver from the remineralization cartridge (0.01 ppm, far below health guidelines).
• We saw an increase in zinc and manganese, safe at detected levels.

Cloud RO – Remineralization

The Cloud removes minerals during filtration and reintroduces some through a remineralization stage.
Lab results showed low mineral content due to short contact time, but TDS testing suggests levels are higher in regular use.
Mineral content depends heavily on usage and downtime. Manual remineralization is still the most reliable method.

Cloud RO – NSF Certifications

• Certified against NSF standard 58 for TDS reduction (98% reduction rate).
• No other certifications yet, but Cloud is working on it.
• Cloud provides its own NSF test data for chlorine, chloramine, lead, VOCs, forever chemicals, chromium 6, nitrate, and fluoride.
• Taste and odor of water were perfect.

Cloud RO – Usability

Installation was straightforward, packaging and instructions were excellent.

1. Cut hole in countertop and install faucet.
2. Connect faucet tubing, turn off cold water line, install T-valve.
3. Reconnect supply line, drill drain pipe for clamp, connect tank tube.
4. Install base, connect tubing, seat cartridge.
5. Turn water back on, flush system by filling and purging 3 tanks.

Filter replacement is easy with twist-in modular filters.

Cloud RO – Speed and Tank Performance

• Filled an 8-ounce cup in 6 seconds (average speed).
• Dispensed 2.2 gallons from a full tank before flow slowed.
• Tank refilled in just over 23 minutes (fastest in comparison).

Cloud RO – App and Features

The free Cloud app connects via Bluetooth.

• Tracks tap water TDS, filtered TDS, and remineralized TDS averages.
• Shows water consumption, tank level, and battery status.
• Battery lasts 2+ years and is replaced with filter sets.
• App calculates filter replacement timing based on use.
• pH and mineral tabs are estimates only.

Cloud RO – Wastewater

• 0.56 gallons wasted per 1 gallon purified with tank off.
• About 1:1 ratio with tank on, best among tank-based ROs.
• Achieved via permeate pump and electronic shutoff valve.

Cloud RO – Design and Costs

• Clean design, faucet in 4 finishes.
• Filter replacement includes battery recycling program.
• $549 with discount code.
• 1-year warranty and satisfaction guarantee.
• $200 annual filter cost including battery.

Cloud RO – Summary

1. Top performer among 19 filters.
2. Great lab results, NSF 58 certified, more certifications coming.
3. Includes remineralization, though mineral content varies.
4. Perfect taste and odor.
5. Easy to install, prime, and use. Excellent wastewater ratio.
6. High build quality.
7. Free app adds useful monitoring.
8. Reasonable upfront and yearly costs.

Waterdrop G3P600 and X12 – Introduction

Next up is another reverse osmosis system — the Waterdrop G3P600, our second-highest rated system. Alongside it is the Waterdrop X12, a newer and faster version, though more expensive.

Both are tankless RO systems that filter water on demand using an electric pump, providing continuous water flow.

Waterdrop G3P600 and X12 – Lab Testing

• Both removed most contaminants to 100%.
• Boron reduced 33%, strontium 94% reduced, nitrate and fluoride partially reduced.
• X12 removed slightly more boron, slightly less strontium.
• X12 includes remineralization, G3P600 does not.
• X12 includes UV light treatment (not tested, but harmless).

Waterdrop G3P600 and X12 – NSF Certifications

• G3P600: NSF 42, 53, 58 for TDS, fluoride, cadmium, chromium 6, selenium, chlorine, PFOA & PFOS. TDS reduction 93.59%.
• X12: NSF 42 and 58 for chlorine and TDS. TDS reduction 94.6%.
• Both provide their own test data for other contaminants.

Waterdrop G3P600 and X12 – Installation

1. Turn off cold water supply, disconnect line, install feed water adapter, reconnect line.
2. Install faucet through sink hole and secure.
3. Drill hole for drain saddle (saddle slightly large, fixed with foam board).
4. Place RO system under sink, connect tubing.
5. Connect faucet power cord and power adapter.
6. Install filters, turn on supply and power.
7. G3P600 flushes for 5 minutes automatically, then faucet runs for 30 minutes to prime.
8. X12 flushes automatically for 30 minutes post-installation.

Both systems feel high-quality. The X12 shipped with pre-installed filters that leaked until reinstalled.

Waterdrop G3P600 and X12 – Everyday Use

• G3P600: fills an 8-ounce cup in 7 seconds.
• X12: fills in 4.25 seconds.
• X12 faucet has button and display for selecting dispense amounts (5–64 ounces or continuous).
• Faucet Mode smooths flow but prevents fridge hookup.
• Energy Saving Mode reduces noise and consumption.
• Both have accurate TDS displays and filter life indicators.
• Filter replacement is twist-in and simple.

Waterdrop G3P600 and X12 – Wastewater

• G3P600: 0.75 gallons wasted per gallon purified.
• X12: 0.5 gallons wasted per gallon purified.
• Both auto-flush (G3P600: 4.5 cups after 5 minutes idle, X12: 6 cups after 10 minutes idle).
• Large-volume dispensing drastically improves ratios (e.g., 1 gallon → ~1 gallon wastewater).
• Disabling auto-flush possible on X12 but not recommended.

Waterdrop G3P600 and X12 – Costs

• G3P600: $539, 1-year warranty, discount code available. Annual filter cost ~$145 (less with subscription).
• X12: $1,299 (discounted ~$1,000–1,100), 2-year warranty. Annual filter cost ~$175 (less with subscription).

Waterdrop G3P600 and X12 – Summary

1. Best-performing tankless RO systems in our comparison.
2. Excellent filtration in lab results.
3. NSF certifications present, though X12 could use more.
4. Perfect taste and odor.
5. Fast filtration, especially X12.
6. High-quality design, easy to install and maintain.
7. Low wastewater ratios if dispensing in large volumes.
8. Auto-flushing adds wastewater.
9. G3P600: reasonable price. X12: premium price.

Epic Smart Shield – Introduction

Great! Next up is our favorite regular under sink water filter – one that doesn’t rely on reverse osmosis. The system is also a great budget pick, and it’s the Epic Smart Shield by Epic Water Filters.

Epic Smart Shield – Lab Testing

The Epic Smart Shield did best in our lab testing among all regular under sink filters.

• All undesirable impurities were removed to 100% except boron (50%), strontium (76%), fluoride (no reduction), and nitrate with a minimum reduction rate of 74%.
• Filtered water was flawless aesthetically speaking.
• Certified against NSF standards 42, 53, and 401 (IAPMO certified).
• Additional NSF test data for organics, radiological elements, and 2 microorganisms.

Epic Smart Shield – Design

• Uses a single filter stage: a coconut shell carbon block rated at ~1 micron.
• Space-saving and sturdy design.

Epic Smart Shield – Installation and Usability

1. Install an adapter on the cold water inlet.
2. Connect faucet tubing to the adapter.
3. Mount the Epic Smart Shield to cabinet wall with screws (or Velcro strips if preferred).
4. Optional: Install the dedicated faucet by inserting tubing through sink hole and connecting to valve.
5. If using the existing kitchen faucet, note that cold water flow may reduce significantly depending on supply.
6. Turn on adapter knob and system is ready.

Everyday use is straightforward.

• Dedicated faucet is simple and modern.
• Strong flow: dispensed 1 cup in 2.25 seconds (faster than competitors).
• Filter replacement is quick due to modular design.
• No filter life indicator.
• Replacement cartridges may go out of stock, so it’s wise to keep a spare.

Epic Smart Shield – Costs

• Price: $129–160 depending on faucet option.
• 20% discount code available (no subscription required).
• Filter life: 651 gallons. Estimated annual cost ~$175 (higher for single-stage system).
• Subscription: 15% discount on replacement filters.
• Recycling program: mail 3 used cartridges → receive 1 free new cartridge.

Epic Smart Shield – Pros and Cons

• Pros:
  • Lifetime warranty.
  • Discounts for veterans, healthcare workers, students.
  • Filter recycling program with free replacements.
• Cons:
  • Users who connect to kitchen faucet sometimes report slow flow.

Epic Smart Shield – Summary

1. Simple, effective, and extremely fast under sink filtration.
2. Great usability and space-saving design.
3. Lifetime warranty and extra discounts available.
4. Strong recycling program with real benefits.
5. Slow flow possible if using regular faucet—dedicated faucet recommended.

Other Options – Aquasana SmartFlow

• Best lab testing results, flawless filtered water.
• All relevant NSF certifications.
• Achieved the highest overall filtration score in our comparison.
• Quality not as high as competitors, small leak at faucet base.
• Mixed Amazon reviews.
• Price: $200–250 with discount code (cheap compared to performance).

Other Options – US Water Systems All American & Home Master TMHP-L

• Both did really well in testing.
• Interesting if you prefer Made in USA products (note: tanks are imported).
• Home Master TMHP-L uses UV module (not US-made).
• Home Master remineralizes water twice – before and after the tank.

Other Options – APEC ROES-50 Essence

• Best option for tight budgets.
• Price: as low as $200.
• Performed really well in testing.
• Filter replacements: $50–100 annually (very low ongoing cost).

Other Options – AO Smith AO-US-200 & Culligan US-EZ-4

• AO Smith AO-US-200:
  • Almost as good as Epic Smart Shield in lab results.
  • Mixed customer reviews on Lowe’s website.
  • Much better reviews on Amazon.
• Culligan US-EZ-4:
  • Strong lab results, close to Epic Smart Shield.
  • Feed water adapter didn’t fit supply valve, no adapter included.
  • Parts felt cheap, especially faucet.

Final Wrap-Up

Remember: You can check our full analysis of all 19 under sink water filters including their lab reports in our Google sheet. Also check the sheet and the description box for our links and discount codes in case you want to make a purchase.

We also have a comparison of 26 different countertop water filters and lots of other videos—so why not check our channel?

And please consider subscribing, hit the like button if you want more content like this, and feel free to ask questions in the comments below or share your own experience with these or other water filters. You can also let us know which filters you would like us to review next.

Thanks so much for watching — and we’ll see you in the next one!