iSpring CU-A4
Score: 72/100
Express Water RO5DX
Score: 85/100Rankings
The Express Water RO5DX is a 5-stage reverse osmosis system that provides high-quality purified water with NSF/ANSI 58 certification and alkaline remineralization. Its main trade-off is the production of wastewater and the need for regular filter maintenance. It is best suited for households of 4+ people seeking reliable daily drinking water with improved taste.
The iSpring CU-A4 is a compact, tankless 4-stage ultrafiltration system that removes up to 99% of 700 contaminants while retaining beneficial minerals and producing zero wastewater. It lacks independent third-party testing data and does not reduce TDS, which are limitations for users seeking comprehensive purification. It is best suited for apartment dwellers and RV owners with limited under-sink space who prioritize mineral retention.
| Attribute | | |
|---|---|---|
0.5 gallons per minute | 0.8 gallons per minutebest | |
6 months | 12 monthsbest | |
4 | 6best | |
— | 50 gallonsbest | |
1 yearsbest | 1 yearsbest | |
| ↓ lower better | 12.5 inchesbest | 15 inches |
| ↓ lower better | 4.5 inchesbest | 5 inches |
| ↓ lower better | 10.5 inchesbest | 14 inches |
Click an attribute name to sort · Green = best, red = worst (relative to this comparison)
| Attribute | | |
|---|---|---|
Dimensions & Fit(3) | ||
Height (inches) | 12.5 inches | 15.0 inches |
Width (inches) | 4.5 inches | 5.0 inches |
Depth (inches) | 10.5 inches | 14.0 inches |
Performance & Filtration(7) | ||
Certifications | NSF/ANSI | NSF/ANSI 58 |
Contaminants Removed | Lead, Chlorine, PFAS, Arsenic, Heavy Metals, Chloramine, Hydrogen Sulfide, Rust, Sand, Dirt | Lead, Chlorine, Fluoride, Arsenic, PFAS, Bacteria |
Flow Rate (gallons per minute) | 0.5 gallons per minute | 0.8 gallons per minute |
Filter Life (months) | 6 months | 12 months |
Filtration Stages | 4 | 6 |
Filtration Technology | Ultrafiltration | Reverse Osmosis |
TDS Reduction (percent) | 0 percent | 93-99 percent |
Features & Accessories(1) | ||
Remineralization | false | true |
Installation & Compatibility(1) | ||
Installation Type | Under-sink | Under Sink |
Products in the top-left offer the best value (high score, low price).
The search results consist primarily of manufacturer product pages and retailer listings, with no independent professional reviews or third-party testing data included. Consequently, there is no expert editorial assessment available to validate the system's actual performance relative to the manufacturer's claims regarding contaminant removal and durability.
The provided data does not contain user reviews, customer testimonials, or recurring feedback patterns from everyday consumers. While Home Depot lists 81 customer questions and answers, the specific content of this user feedback is not included in the research data.
Professional reviewers highlight the RO5DX's NSF/ANSI 58 certification as a key strength, validating its TDS reduction capabilities and material safety. While experts note that the certification does not cover the full range of 158 claimed contaminants, they consider TDS reduction the most important metric for RO systems. Hands-on testing confirmed a 93% TDS reduction rate, though some TDS creep was observed during idle periods. The pre-assembled kit is praised for simplifying installation.
Users generally praise the system for its reliable performance, compact size, and the peace of mind provided by NSF certification. The all-in-one kit format is appreciated for its convenience, and users report a noticeable improvement in water taste. Maintenance is described as simple and manageable for non-technical users.
