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Head-to-head · Best Under-Sink Water Filters

Clearly Filtered 3-Stage Under the Sink vs Waterdrop G3P800 Tankless Reverse Osmosis System

Which is the better buy? Side-by-side on rating, price, strengths, and watch-outs — with the published ratings we averaged to get there.

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The short answer

Waterdrop G3P800 Tankless Reverse Osmosis System is the only one of the two with a published score (4.5); Clearly Filtered 3-Stage Under the Sink has none, so this is not a close call so much as an unmeasured one. Waterdrop G3P800 Tankless Reverse Osmosis System is best for: city-water households that want fast, thoroughly purified drinking water on tap. Read the strengths below before deciding.

Clearly Filtered 3-Stage Under the Sink
Ranked #5 in Best Under-Sink Water Filters
Clearly Filtered 3-Stage Under the Sink
Unrated3 sources$550as of Oct 10

The Clearly Filtered 3-Stage is the broad-spectrum carbon system, independently tested to reduce 232+ contaminants, including fluoride, lead, PFAS and arsenic, while wasting no water. Its 2,000-gallon filter life is among the longest here. Two catches: it's the costliest in this group, and it carries only one full NSF certification despite extensive third-party testing. For maximum contaminant breadth without RO, it's excellent.

Strengths
  • — Independently tested to reduce 232+ contaminants including fluoride, lead, PFAS and arsenic
  • — Long 2,000-gallon filter life (per Bos Water), roughly 9 to 15 months between changes
  • — No water waste, no drain line or dedicated faucet needed
Watch-outs
  • — Holds only one full NSF certification (NSF 42) despite broad third-party testing, which Bos Water notes is less reassuring than formal certification
  • — Significantly more expensive upfront than other carbon systems
  • — Some owners report reduced water pressure over the filter's life
$550 · Buy at clearlyfiltered.comFull review →
Waterdrop G3P800 Tankless Reverse Osmosis System
Higher ratedRanked #1 in Best Under-Sink Water Filters
Waterdrop G3P800 Tankless Reverse Osmosis System
1 source$759as of Oct 17

The Waterdrop G3P800 is a tankless under-sink reverse osmosis system rated at 800 gallons per day. It uses three filter cartridges and an inline UV sterilizer, and needs an electrical outlet. Water Filter Guru scored it 9.21/10 after lab testing: it removed every contaminant found above health guideline levels and measured 886.54 GPD. Bob Vila praised its quick, leak-free filter changes and its 3:1 rated pure-to-drain ratio, and Reviewed noticed a clear improvement in taste. It suits city-water households that want fast, thorough purification. Well-water users, and anyone wanting minerals left in or a simple install, should look elsewhere.

Strengths
  • — Water Filter Guru measured 886.54 GPD, above the 800 GPD rating
  • — Removed every contaminant found above health guideline levels in lab tests
  • — Wastes less water than most tankless RO systems Water Filter Guru tested
Watch-outs
  • — Installation is involved; Reviewed had to hire a plumber
  • — No built-in remineralization; the add-on filter is sold and fitted separately
  • — The unit makes an audible groan when dispensing water
$759 · Check Price on AmazonFull review →

How they stack up

Clearly Filtered 3-Stage Under the Sink

The Clearly Filtered 3-Stage Under the Sink is tested to reduce 232+ contaminants including fluoride, which the Frizzlife MP99 and Waterdrop 15UA do not reduce. It holds only one full NSF certification, where the Aquasana Claryum AQ-5300+ is certified to NSF/ANSI 42, 53 and 401. Its 2,000-gallon filter life is longer than the Aquasana's 800 gallons and far shorter than the Waterdrop's 16,000, and it costs far more than all three.

Waterdrop G3P800 Tankless Reverse Osmosis System

Unlike the Aquasana Claryum AQ-5300+, which the page recommends for keeping minerals in, the G3P800's RO membrane removes nearly all of them unless an add-on remineralization filter is fitted. It also needs an under-sink power outlet and a drain connection. At $759 it is a heavier investment than the Waterdrop 15UA or Frizzlife MP99, both recommended on this page for budget buyers.

Specs side-by-side

SpecClearly Filtered 3-Stage Under the SinkWaterdrop G3P800 Tankless Reverse Osmosis System
Filtration3-stage Affinity media—
CertificationsNSF/ANSI 42, 372 (broad third-party testing)NSF/ANSI 42, 53, 58 and 372
Contaminants Reduced232+ (fluoride, lead, PFAS, arsenic)—
Filter Life2,000 gallons / 9-15 months6 months (CF), 12 months (CB), 24 months (RO)
Mineral RetentionPartial: Water Filter Guru's lab measured calcium -92%, magnesium -6%, hardness -68%—
Water WasteNone—
FaucetUses existing faucet (no separate faucet)—
Reduction Rate90-99% across tested contaminants—
Type—Tankless reverse osmosis with UV sterilizer
Rated Output—800 gallons per day
Dimensions—18.12 x 5.67 x 17.72 in
Filters—Sediment/carbon (CF), carbon block (CB), RO membrane
Rated Pure-to-Drain Ratio—3:1
Warranty—1 year
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