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

Clearly Filtered 3-Stage Under the Sink vs Cloud RO Under-Sink 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

Cloud RO Under-Sink Reverse Osmosis System is the only one of the two with a published score (4.4); Clearly Filtered 3-Stage Under the Sink has none, so this is not a close call so much as an unmeasured one. Cloud RO Under-Sink Reverse Osmosis System is best for: households that want app-monitored reverse osmosis water without an under-sink outlet. 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 →
Cloud RO Under-Sink Reverse Osmosis System
Higher ratedRanked #2 in Best Under-Sink Water Filters
Cloud RO Under-Sink Reverse Osmosis System
2 sourcesall derived

The Cloud RO is a battery-powered, app-connected under-sink reverse osmosis system with eight filtration stages, remineralisation, a 2.8-gallon tank and a rated 80 gallons per day. The Spruce named it its best smart system after a year of use, citing easy setup, useful app monitoring and alerts, and enough output for a large household; Good Housekeeping found it compact, quiet and noticeably better tasting than NYC tap water. Both flag the cost: Good Housekeeping puts the starting price at about $600 with $200 replacement filters, and The Spruce notes a 1:1 waste ratio. It suits households that want RO water with real-time monitoring; buyers on a budget or short of cabinet space should look elsewhere.

Strengths
  • — The Spruce found setup easy, with well-labelled lines and fittings
  • — App shows tap and filtered water quality and sends filter-change alerts
  • — Battery powered, so no outlet is needed under the sink
Watch-outs
  • — Costs more than many RO systems, and replacement filters cost about $200
  • — 1:1 waste ratio, more wasteful than The Spruce's top iSpring pick
  • — Included faucet feels a little flimsy, and flow sputters on first use each day
Buy at cloudwaterfilters.comFull review →

Derived means the reviewer published no score, so one was inferred from their written verdict. Everything else is a number the publisher printed. How we rank.

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.

Cloud RO Under-Sink Reverse Osmosis System

Unlike the Waterdrop G3P800 Tankless Reverse Osmosis System, the Cloud RO stores water in a 2.8-gallon tank and runs on a battery rather than mains power. Like the APEC Water ROES-PH75 Essence Alkaline system it adds minerals back after RO filtration, but it is priced from about $600 and adds app monitoring; the Aquasana Claryum AQ-5300+ is a non-RO filter for buyers who want to avoid a tank altogether.

Specs side-by-side

SpecClearly Filtered 3-Stage Under the SinkCloud RO Under-Sink Reverse Osmosis System
Filtration3-stage Affinity media—
CertificationsNSF/ANSI 42, 372 (broad third-party testing)—
Contaminants Reduced232+ (fluoride, lead, PFAS, arsenic)—
Filter Life2,000 gallons / 9-15 months—
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—Under-sink reverse osmosis with tank
Dimensions—11 x 7 x 16 inches
Daily Production Rate—80 gpd
Filtration Stages—8
Tank Capacity—2.8 gallons
Power—Battery
Waste Ratio—1:1
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