One of the most thoroughly certified reverse-osmosis systems you can buy, with the fastest flow and best water efficiency in its class. The catches are a premium price and the need for an outlet under your sink.
We may earn a commission if you buy through our links, at no extra cost to you. It never affects our scores.
The RO system for people who want it all filtered, fast
The Waterdrop G3P800 is a tankless reverse-osmosis system that solves the two things people dislike most about RO: the slow trickle and the bulky storage tank. It pushes 800 gallons per day through a compact under-sink unit with a smart faucet that shows your live TDS reading, so you can watch it work. In independent lab testing it reduced total dissolved solids by about 85% and drove all fourteen tested PFAS compounds to non-detect, alongside strong lead, fluoride, and disinfection-byproduct reduction.
What sets it apart on our scoring is the certification stack. It carries NSF/ANSI 42, 53, 58, and 372, which is one of the broadest in the category, so its core claims are independently verified rather than just tested. It’s also efficient for RO, sending three parts filtered water to drain for every one wasted, the reverse of older systems.
Best for: homeowners who want the widest certified contaminant removal with fast, on-demand flow, and who have (or can add) a power outlet under the sink.
How it scored, category by category
Each category is weighted into the overall score. Contaminant reduction carries the most weight, and the broad NSF certification is what lifts this system near the top of our rankings.
What it removes
The figures below come from Waterdrop’s NSF/ANSI test data and independent lab testing. We note the standard each claim is certified against.
| Contaminant | Reduction | Certified to |
|---|---|---|
| PFAS (14 analytes tested) | Non-detect | NSF 58 |
| Lead | 99%+ | NSF 58 |
| Fluoride | Up to 98% | NSF 58 |
| Total dissolved solids | ~85% | NSF 58 |
| Chlorine (taste & odor) | >99% | NSF 42 |
Reduction figures are from Waterdrop’s NSF/ANSI certification data and independent testing (Quality Water Lab). Real-world results vary with your source water, temperature, and pressure, and the rated 800 GPD flow drops at lower household water pressure.
Pros and cons
What we liked
- One of the broadest NSF certification stacks in RO
- Fastest flow here (800 GPD), tankless and compact
- Efficient 3:1 pure-to-drain ratio
- Smart faucet with a live TDS readout
Worth considering
- Needs a 110V outlet under the sink (may mean an electrician)
- Premium price versus tanked RO systems
- No remineralization; RO water can taste flat (add-on sold separately)
What actual owners report
Our score reflects certified performance. Owner sentiment, summarized from verified buyer and long-term-use reviews, is strongly positive, with one recurring practical gripe.
Owners are among the most satisfied in the RO category on flow and clarity. The most common frustration is logistical, not about the water: discovering at install time that they need a power outlet under the sink.
Owners consistently praise
- Fast, on-demand water with no tank and no waiting
- Frees up cabinet space; clean, compact install
- The live TDS display and noticeably cleaner taste
Common complaints
- The under-sink outlet requirement, often missed at purchase
- Flat taste from RO unless you add the remineralization filter
- Occasional filter-fault errors reported at first replacement
Summary of recurring themes across verified buyer and independent long-term reviews, current as of August 2026. We report the patterns we see, positive and negative, and never cherry-pick.
The details
Common questions
Does the G3P800 need electricity?
Yes. Like most tankless RO systems, it uses a booster pump and needs a standard 110V outlet under the sink. If you don’t have one there, budget for an electrician. It’s the single most common surprise for buyers, so check before you order.
Does it waste a lot of water?
No, it’s efficient for reverse osmosis. Its 3:1 pure-to-drain ratio means three parts filtered water for every one sent to drain, which is the reverse of many older RO systems that waste several gallons per gallon produced.
Does it remove PFAS and fluoride?
Yes. It’s NSF/ANSI 58 certified reverse osmosis, and in independent testing all fourteen PFAS analytes came back non-detect, with fluoride reduced by up to 98%. For a full look at PFAS options, see our certified PFAS filters guide.
Does RO make the water taste flat?
It can. Reverse osmosis removes dissolved minerals along with contaminants, which some people find makes water taste flat. Waterdrop sells a remineralization filter (around $30) that adds calcium and magnesium back if you prefer that taste.
Should you buy it?
If you want the widest certified contaminant removal with fast, tankless flow, the Waterdrop G3P800 is one of the best reverse-osmosis systems on the market and an easy recommendation, provided you have a power outlet under the sink and are comfortable with the premium price. If you’d rather avoid any installation, our no-plumbing pick is the AquaTru Carafe; if you want RO on a tighter budget, compare the field on our best filters page.
Check price on Amazon ›