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

Waterdrop 15UA 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); Waterdrop 15UA 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.

Waterdrop 15UA
Ranked #6 in Best Under-Sink Water Filters
Waterdrop 15UA
Unrated3 sources$48.73as of Sep 28

The Waterdrop 15UA is the value champion of under-sink filters, with NSF/ANSI 42, 53 and 372 certified reduction of PFAS, lead, chlorine and heavy metals for under $100. The headline feature is a 16,000-gallon, 24-month filter life that keeps running costs minimal, alongside a tool-free under-5-minute install that connects directly to your existing faucet. Being single-stage, its contaminant breadth is narrower, but the value is unbeatable.

Strengths
  • — Very long 16,000-gallon / 24-month filter life keeps running costs low
  • — Connects directly to your existing faucet, no separate faucet or drilling
  • — Tool-free, under-5-minute push-to-connect installation
Watch-outs
  • — 0.75 GPM flow is modest compared with fast-flow rivals
  • — Direct-connect design filters all faucet water, not a dedicated line
  • — Does not reduce fluoride or total dissolved solids
$48.73 · Check Price on AmazonFull 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

Waterdrop 15UA

The Waterdrop 15UA is a single-stage carbon block with a 16,000-gallon filter life, far longer than the 2,000 gallons of the Clearly Filtered 3-Stage Under the Sink or the 800 gallons of the Aquasana Claryum AQ-5300+. Its 0.75 GPM flow is below the 1.4 GPM of the Frizzlife MP99, which needs a hole for its dedicated faucet. It does not reduce fluoride, which the Clearly Filtered does.

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

SpecWaterdrop 15UAWaterdrop G3P800 Tankless Reverse Osmosis System
FiltrationSingle-stage carbon block—
CertificationsNSF/ANSI 42, 53, 372NSF/ANSI 42, 53, 58 and 372
Contaminants ReducedPFAS, PFOA/PFOS, lead, chlorine, heavy metals—
Filter Life16,000 gallons / 24 months6 months (CF), 12 months (CB), 24 months (RO)
Flow Rate0.75 GPM—
InstallDirect connect, tool-free, <5 min—
FaucetUses existing faucet—
MaterialBPA-free, lead-free—
Capacity16000 gal—
Dimensions3.9"L x 3.6"W x 16.7"H18.12 x 5.67 x 17.72 in
Type—Tankless reverse osmosis with UV sterilizer
Rated Output—800 gallons per day
Filters—Sediment/carbon (CF), carbon block (CB), RO membrane
Rated Pure-to-Drain Ratio—3:1
Warranty—1 year
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