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Under-sink reverse osmosis often means handing cabinet space over to a storage tank. The Waterdrop G3P800 skips the tank entirely.
It is the most-reviewed tankless RO system Waterdrop makes, and it is rated for 800 gallons a day. The price is $878.99, down from $1,028.99 with code WDG3P800.
We combed through the spec sheet, a lab test from an independent site and a hands-on write-up by a national outlet. The goal was to judge whether it earns that price.
Design and Included Hardware
A 0.0001-micron RO membrane sits at the center of this tankless design, which has 10 filtration stages. Waterdrop lists the installation as a 30-minute DIY job.
The package contains the following:
- Smart LED faucet
- Power adapter
- Built-in UV sterilizer
- Mounting hardware and tubing
- Drain saddle
- Feed water adapter
Certifications and Water Savings
The G3P800 carries NSF/ANSI 42, 53, 58 and 372 certification. That verifies it reduces chlorine, taste and odor, TDS and lead.
Waterdrop also makes broader contaminant claims, such as PFOA and PFOS reduction of up to 99 percent.
Its 3:1 pure-to-drain ratio cuts waste to roughly a third of what older tank-based RO designs lose.
What the Independent Lab Found
The testing site WaterFilterGuru scored the G3P800 at 9.21 out of 10. It called this the highest-scoring tankless under-sink RO system the site has tested.
Measured output reached 886.54 GPD. That beats Waterdrop’s own claim of 800 GPD.
The test also tracked contaminant reduction:
- Selenium: 100 percent
- Fluoride: 78 to 100 percent
- Hexavalent chromium: up to 100 percent
- Total dissolved solids: a 93 to 95 percent drop
These figures come from lab measurements, not from marketing copy.
Owner and Reviewer Feedback
On Waterdrop’s own site, the G3P800 holds 4.9 out of 5 across 101 reviews. Amazon offers a much larger sample, with 4.6 out of 5 across 3,677 reviews. Scores that stay steady at that scale are a good sign.
The managing editor at Reviewed.com tried it hands-on. She said the filtered water had a purer texture than tap water, and that it noticeably reduced the mineral buildup in her coffee maker. Compared with a fridge dispenser, she judged the taste a real step up.
Her complaints were practical and had nothing to do with water quality. Water comes out more slowly than from an ordinary kitchen faucet, and it does not get as cold as fridge-dispensed water.
The 30-minute DIY claim did not hold up for her, and she ended up hiring a plumber. She said anyone without a lot of plumbing and construction experience should bring in a professional.
Trade-Offs Before You Buy
- The warranty lasts 1 year. The longer 2-year coverage Waterdrop offers applies only to eligible X Series systems, not to this model.
- Installation costs extra. If you are not confident with under-sink plumbing, budget for a plumber.
- Filters need tracking. Like any RO system, this one has ongoing filter costs that add up.
Our Verdict
This system suits anyone who wants lab-verified RO filtration without giving up under-sink cabinet space to a tank. It backs its price with outside test data and plenty of steady reviews.
Treat installation as its own line item. Also check the current return window before you buy, because promo pricing sometimes ties to final-sale terms.