The G3P600 is the machine that made reverse osmosis acceptable in a normal kitchen, and that is a serious compliment: it removes the 3-gallon tank that made a lot of people give up. It also costs two to three times a classic five-stage and makes you dependent on one brand for consumables. Here are both sides, in order.
What it genuinely changes
It gives you back a cabinet. That is the central argument and it is not cosmetic. A classic system is a row of filter housings plus a pressurized tank the size of a large ball, to be wedged next to the P-trap and the trash. The G3P600 stands as one vertical block. Under a 24-inch sink base, that is the difference between "it does not fit" and "it fits".
It does not store water. A direct and underrated consequence: in a tank, RO water can wait days between uses. That is the hygiene weak point of the tanked architecture, and on-demand production eliminates it by design.
It wastes half as much. A five-stage without a pump sends 3 to 4 gallons to drain per gallon produced; this one states 2:1. On a gallon and a half of drinking water a day, that is 3 gallons wasted instead of 6. On the bill the gap is a few dollars a year, and I am not going to pretend otherwise. On principle, it changes the decision for anyone the waste was holding back.
The flow is a real comfort. 600 GPD against 75 for a classic membrane. The glass fills continuously, without the trickle you get when a tank has run dry.
What makes me keep it: the certification
In a market where "8 stages" means nothing checkable, the G3P600 carries NSF/ANSI 58 (TDS reduction by reverse osmosis) and NSF/ANSI 372 (lead-free wetted materials) certification. Those are third-party verifications, to be carefully distinguished from the "meets NSF standards" wording product pages love, which commits nobody but the copywriter.
It is the only genuinely verifiable item on the whole spec sheet. At this price point I consider it disqualifying to lack it: a $550 tankless without third-party certification does not deserve your money.
One precision on what 58 covers, because it gets stretched in marketing: the standard certifies TDS reduction. Specific claims — lead, arsenic, PFAS — are separate certified reductions, listed individually on the performance data sheet. Reverse osmosis does handle all three well by its physics, but "NSF 58 certified" on its own is not a PFAS claim. Ask for the data sheet.
The three reservations, and they matter
The cartridges are proprietary. This is my main reservation and it is structural. This is not the standard 10-inch format: you will buy refills from Waterdrop or its resellers, at whatever price they set, for as long as the range exists. On a machine meant to last ten years, that is a bet on one brand's commercial continuity. The three-second tool-free change is pleasant; it is paid for in independence. It is exactly the inverse of the criterion I defend in my comparison method.
It needs an outlet. Pump and electronic faucet oblige. In an older kitchen with no outlet under the sink, that is a disqualifying factor, not a detail to sort out later with an extension cord.
The price. Around $549 against $219 for an entry-level five-stage. Less frequent consumables narrow the gap over ten years without closing it. If your cabinet is roomy and the wastewater does not concern you, the iSpring RCC7 does the same filtration job for a good deal less.
Against the classic five-stages
| Model | Stages | Output | Tank | Rating | Price | |
|---|---|---|---|---|---|---|
Waterdrop G3P600 Waterdrop | 8 | 600 gpd | 0 gal | 4.5/5 | $549 | See price |
iSpring RCC7 iSpring | 5 | 75 gpd | 3.2 gal | 4.4/5 | $249 | See price |
APEC ROES-50 Essence APEC Water | 5 | 50 gpd | 4 gal | 4.3/5 | $219 | See price |
Prices shown are indicative · affiliate links.
The detailed comparison of the two architectures, with the cases where each wins, is in tankless reverse osmosis: what you gain, what you give up.
Waterdrop G3P600
Strong points
- Tankless: gives you back a whole cabinet under the sink
- 600 GPD on demand — a glass fills in seconds, and no water sits in a tank
- 2:1 drain ratio, twice as good as a classic 5-stage
- NSF/ANSI 42, 53, 58 and 372 certified: the TDS reduction is verified by a third party
Weak points
- Proprietary cartridges: you depend on Waterdrop for consumables
- Needs an outlet under the sink (pump and LED faucet)
- Two to three times the price of a standard 5-stage
Where to buy
- Amazon$549 See price
How to check it is working
The faucet shows a TDS indicator, which is convenient but remains a number the machine reports about itself. The independent check costs about fifteen dollars: a TDS meter read at the cold tap, then at the RO faucet. A healthy membrane rejects more than 90% of dissolved solids. The day that rate slips under 80%, the membrane is due for replacement, whatever the indicator says.
HM Digital TDS-EZ meter
Strong points
- The simplest way to check an RO system is still doing its job
- Reads in seconds, factory calibrated, 0–9990 ppm
- Cheap enough to keep under the sink
Weak points
- TDS is not a health measure: it says how much is dissolved, not what
- No automatic temperature compensation, so cold and warm samples do not read alike
- Says nothing about lead, PFAS or bacteria
Where to buy
- Amazon$15 See price
What this review rests on
It has not run under my sink for two years: my kitchen has one water line and it is occupied, and I write that on every page rather than hiding it at the bottom. This review cross-checks verifiable specifications, the third-party certification (the only element independent of the manufacturer's own claims), long-run user feedback, and my experience of maintenance and TDS measurement. What I cannot judge, I do not judge: how the pump holds up at five years, and how cartridge prices evolve, are two unknowns — and they are precisely the two that will decide this machine's real value. My full checklist is in my reviews page.
On installation, this model needs an outlet under the sink on top of the usual tee and countertop hole, and that is what trips people up most often: few sink cabinets have one. If yours does not, or if drilling the countertop stops you, I can point you to an installer.
Would you rather have a pro install it?
Fitting an under-sink RO system means tapping the cold line and drilling the countertop, which is not for everyone. If it's not your thing, leave me your details: I'll connect you with a trusted installer near you, with no obligation on your side.
