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.
Full review
Cleared every contaminant above health guidelines in lab tests
Water Filter Guru sent before-and-after samples to a lab. The G3P800 eliminated every contaminant found above the Health Guideline Level, including all three trihalomethanes and 100% of the uranium. Without the remineralization filter it cut fluoride by 78.95%, and with the filter by 100%. It reduced total dissolved solids by about 95% and removed chlorine completely in strip tests. Its weak spot was boron, reduced by only 19%. TDS creep after an overnight idle was just 33 PPM. Bob Vila's faucet display read 8 PPM TDS, and Reviewed noticed a huge difference from tap water.
Fast flow with less wastewater
Speed was a standout. Water Filter Guru timed repeated fills and worked out 886.54 gallons per day, above Waterdrop's 800 GPD claim. It was the fastest flow the site had recorded from any RO system. Reviewed found it fills a 6-ounce cup in about five seconds, though a carafe still takes longer than with a standard faucet. Waterdrop rates the pure-to-drain ratio at 3:1. Water Filter Guru measured 2.21:1 on a 64-ounce draw in cold 58.3°F feed water, which was still one of the best results it had seen from a tankless under-sink unit.
Installation is the main hurdle
The reviewers disagreed on installation. Bob Vila finished in under an hour with push-to-connect fittings and an included line cutter, though it first had to add a GFCI outlet under the sink. Water Filter Guru took around two hours and counted nine potential leak points, but its initial flush took just 35 minutes. Reviewed called a plumber and noted the need for a counter hole if using the dedicated smart faucet. Day to day, filters twist out without shutting off the water, and indicators show when each one is due. Bob Vila noted the unit groans audibly while dispensing.
Low running costs, short warranty
Water Filter Guru calculated running costs of about $0.11 per gallon, or roughly $124.75 a year in filters. It ranked that among the lowest per-gallon costs of any system it has tested, and said the system offers exceptional value overall. Its complaints were the separate $30 remineralization filter, which added 0.24 PPM of nitrite until flushed, and a one-year warranty that it found short for the price. The system is designed for treated municipal water, not untreated well water. Reviewed concluded that, even with professional installation, it costs far less than most whole-house filtration systems.
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
- +Filters swap with a quarter-turn and no leaks
- +Reviewed noticed a clear taste difference from regular tap water
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
How it compares
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.
Rating sources
Counts as 4.53/5 in our score — this publisher's 2 scores on the site average 4.40, so its scores are adjusted down to compare fairly with other publishers.
“We scored the Waterdrop G3 P800 9.21/10, the highest score of any tankless under-sink reverse osmosis system we have lab tested.”
Not in the average — we derived this score from the review's words, and a publisher printed a score for this product, so the printed number counts instead.
Not in the average — we derived this score from the review's words, and a publisher printed a score for this product, so the printed number counts instead.
Our 4.5 score is the average of 1 of the scored reviews above, each adjusted for how strictly its publisher scores. 2 derived scores above are not in the average because a publisher printed a score for this product. Ratings marked * were derived from the reviewer’s written analysis or video transcript — the publisher didn’t print an explicit numeric score, so we inferred one from their own words. Click through to verify. More about methodology.
