WaterdropD6 Under Sink Reverse Osmosis System, 600 GPD
The most water-efficient and cheapest-to-run system in Waterdrop’s under-sink range.
$399
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Usability
Usability
On the numbers that matter for running cost, the D6 wins: a 1.5:1 pure-to-drain ratio means it sends half as much water down the drain as the 3:1 flagship for every gallon produced, and its filters cost about $100 a year, the cheapest here. It is also the smallest and lightest under-sink unit at 22.2 lb. The gap is certification — Waterdrop publishes no NSF/ANSI mark for the D6 on its own comparison table, so contaminant claims rest on the manufacturer's SGS test reports rather than a certifier's listing. Six stages is mid-pack. Treat it as the efficiency pick rather than the verified-performance pick.
- 1.5:1 pure-to-drain, the most efficient ratio in the range
- About $100/year in filters, the lowest running cost here
- Smallest and lightest under-sink unit at 22.2 lb
- Push-in cartridge replacement takes seconds
- 600 GPD from a compact chassis
- No NSF/ANSI certification published for this model
- Contaminant claims rest on manufacturer-commissioned lab testing only
- Six stages is mid-pack for the price
- One-year warranty
- Requires an electrical outlet
The D6 is Waterdrop's compact 600 GPD system, notable for a 1.5:1 pure-to-drain ratio — the most water-efficient in the range — and the lowest running cost at roughly $100 a year in filters. Six stages, push-in cartridge changes, and the smallest footprint of any Waterdrop under-sink unit.
Additional information
Specification: Waterdrop D6 Under Sink Reverse Osmosis System, 600 GPD
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Questions answered from our data

Is Waterdrop a good brand?We list 29 Waterdrop products and score 29 of them. Their overall scores run from 5.0 to 7.6, with a median of 6.0, against a median of 5.7 for all 284 products we score.
How much does a reverse osmosis system cost?The 69 reverse osmosis systems we list run from $165 to $3,779, with a median of $367.
How long do reverse osmosis filters last?Of the 69 reverse osmosis systems we list, 64 state a filter life; the most common is 6-12 months (62).
Does reverse osmosis remove microplastics?Six of the 76 reverse osmosis systems we list claim to reduce microplastics.




