Under-sink RO systems have a space problem. A traditional tank-based system means a pressurized 3 to 4 gallon tank sitting in your cabinet alongside the filter housings. In smaller kitchens, that’s often most of the under-sink storage.
Waterdrop’s tankless design solves that. No pressurized storage tank. The system filters on demand, driven by a pump. Smaller footprint, same RO filtration.
This review covers the G2, G3, and D6 models, based on NSF certification data and manufacturer documentation.
What Waterdrop Is
Waterdrop launched in 2015. It’s a Chinese-founded company that sells primarily in the US market through Amazon and their own website. Their product lineup includes under-sink RO systems, countertop units, and pitcher filters.
The under-sink RO line is the main product, and tankless design is their primary differentiator. They sell at a lower price point than name brands like iSpring or Aquasana while targeting similar NSF certification standards.
Waterdrop is not a US company. That matters to some buyers for customer service reasons. US-based iSpring offers comparable performance with domestic customer support if that’s a priority for you.
Tankless vs. Tank-Based RO: What Actually Changes
A traditional under-sink RO system stores filtered water in a pressurized tank. Water flows into the tank at a trickle (RO membranes are slow), and the pressurized tank delivers water instantly when you open the tap. The tank takes up cabinet space.
Waterdrop’s tankless approach uses a pump to push water through the membrane on demand. When you open the tap, the pump runs and delivers filtered water directly. No storage tank, smaller footprint.
The tradeoff: flow rate during use depends entirely on the pump. Some users notice a slight delay or lower pressure compared to tank systems. In practice, for most households filling glasses and cooking pots, the difference isn’t a problem.
On waste water, Waterdrop’s G-series tankless models achieve a 2:1 or better pure-to-drain ratio on their higher-end specs. Traditional tank systems typically run 3:1. That’s a real efficiency advantage.
NSF Certifications
Waterdrop systems carry:
- NSF/ANSI 58 (reverse osmosis performance)
- NSF/ANSI 372 (lead-free components)
Verify the specific model at info.nsf.org before purchasing. Certification applies to individual models, not the brand as a whole. The G2, G3, and D6 have been NSF 58 certified as of this writing, but confirm before you buy.
What RO Removes (Applicable to All Waterdrop RO Models)
Reverse osmosis removes contaminants by forcing water through a semipermeable membrane at pressure. What comes out the other side:
- PFAS compounds reduced by RO membrane
- Fluoride: approximately 90 to 96% reduction
- Arsenic: approximately 95% reduction
- Nitrates: approximately 85 to 93% reduction
- Lead: approximately 95% reduction
- Chromium-6
- Chloramine and chlorine (via carbon stages)
- Dissolved minerals, pharmaceuticals, and other compounds
Test your water before choosing treatment. Source water varies by region and well. Knowing what’s in your water lets you pick the right system for your specific situation.
The Models
Waterdrop G2 P800
800 GPD rated. Tankless. 2:1 pure-to-drain ratio. 7-stage filtration. UV sterilizer included. Priced around $200 to $280 depending on sales.
The UV lamp adds bacteria inactivation to the standard RO filtration. For households on city water with no bacterial concern, this is redundant but harmless. For well water users, UV paired with RO is genuinely useful coverage.
Check current pricing (affiliate link, see disclosure above)
Waterdrop G3 P800
Similar specs to the G2. Improved filter module design with easier twist-lock replacement. Build quality is slightly higher. Priced around $230 to $300.
For most buyers, the G3 is the better choice between the two if the price difference is small.
Check current pricing (affiliate link, see disclosure above)
Waterdrop D6
Smaller, more affordable option. 400 GPD rated. No UV sterilizer. Designed for apartments and smaller households. Priced around $150 to $180.
If you don’t need UV and want to minimize cost, the D6 delivers the same RO filtration at a lower price. Good for apartments where bacteria isn’t a concern.
Check current pricing (affiliate link, see disclosure above)
Waterdrop Pitcher Filters (WD-PT-04)
Waterdrop also sells activated carbon pitcher filters. These are a different category from the RO systems. They reduce chlorine, lead (via NSF/ANSI 42 and 53 testing), and improve taste. They do not remove PFAS, fluoride, or nitrates. If PFAS is your concern, get the RO system, not the pitcher.
Filter Replacement Schedule and Costs
Waterdrop uses composite all-in-one modules rather than individual filter housings. The modules contain multiple filter media combined into a single unit.
| Component | Replaces Every | Notes |
|---|---|---|
| Composite filter | 6 to 12 months | Depends on usage and source water quality |
| RO membrane | 24 months | The main filtration stage |
| UV lamp (G-series) | 12 months | Adds to annual cost |
Annual filter cost: approximately $80 to $120 for G-series. The UV lamp replacement is an added expense that tank-free systems without UV don’t have. Factor this in when comparing total ownership cost.
Waterdrop replacement filters are available on Amazon and their website. The twist-lock design makes replacement straightforward without tools.
Customer Service and Brand History
Waterdrop is a newer brand with less of a track record than iSpring (founded 2009) or Aquasana (founded 2001). Customer service reviews are mixed. Some buyers report smooth experiences. Others have had trouble getting support for issues under warranty.
If you want US-based customer support and a company with a longer service history, iSpring is the comparable option. Both carry NSF 58 certification and offer similar under-sink RO performance. Waterdrop wins on compact form factor and tankless design. iSpring has the edge on support reputation.
How Waterdrop Compares to iSpring
Both are NSF 58 certified under-sink RO systems at similar price points.
Waterdrop differentiates on tankless design (smaller cabinet footprint) and better waste water efficiency (2:1 vs. 3:1 on comparable models). iSpring differentiates on US-based customer service, longer brand track record, and the tank-based model that delivers consistent pressure.
If you have the cabinet space and want proven customer support, iSpring is worth comparing directly. If space is tight and you want the most compact setup, Waterdrop G2 or G3 makes more sense.
The Recommendation
For compact under-sink RO with good efficiency, Waterdrop G2 or G3 is a solid choice at a lower price than name brands. NSF 58 certification is there. Tankless design genuinely helps in tight spaces.
One caution: verify NSF certification for the specific model you’re buying at nsf.org before purchasing. Waterdrop has expanded its product line quickly, and not every model may carry the same certifications.
For a full overview of what NSF 58 certification covers and how it compares to other standards, the NSF certification standards explainer has the breakdown.
The best under-sink RO systems page compares Waterdrop alongside iSpring and other options if you want a side-by-side view.