SLF Water Filtration Comparison · 2026
VIVA21 5-Stage RO
Recommended for shoppers seeking an affordable traditional under-sink RO system with stronger certification positioning than many budget alternatives.
VIVA21 6-Stage Alkaline RO
Recommended
VIVA21 5-Stage RO
Choose the VIVA21 5-Stage for low purchase and maintenance costs; choose the 6-Stage Alkaline version if you specifically want remineralization.
RO Performance & Ownership
Compare RO output, filtration stages, remineralization, contaminant evidence, certifications and ownership cost.
Which Is Right for You?
VIVA21 5-Stage RO
Best for: Budget-conscious households that want a conventional, certified-positioned under-sink RO system with a storage tank and standard-size replacement filters.
Consider if: Budget Under $200, Low Replacement Cost
VIVA21 6-Stage Alkaline RO
Best for: Households wanting a traditional under-sink RO system with remineralization and a dedicated storage tank.
Consider if: Budget Under $300, Want Remineralization
Our Recommendation
VIVA21 5-Stage RO
A strong budget-oriented conventional RO choice for households that have cabinet space and value certification and standard replacement filters over high output and connected features.
VIVA21 6-Stage Alkaline RO
A compelling value-oriented alternative to higher-priced tankless RO systems for households that don't mind giving up cabinet space for a conventional storage tank.
The Short Answer
Choose the VIVA21 5-Stage for low purchase and maintenance costs; choose the 6-Stage Alkaline version if you specifically want remineralization.
Choose the VIVA21 6-Stage if you want an affordable traditional under-sink RO system with alkaline remineralization and stronger certification positioning than many budget RO systems.
Water Filter Comparison FAQs
Answers are generated from the current SLF product records for these two systems.
Which is better, VIVA21 5-Stage RO or VIVA21 6-Stage Alkaline RO?
VIVA21 5-Stage RO is the overall pick for this specific matchup. Choose the VIVA21 5-Stage for low purchase and maintenance costs; choose the 6-Stage Alkaline version if you specifically want remineralization.
Which system has the higher daily filtration capacity?
Both systems have the same rated output in the current SLF records.
Which system offers remineralization?
VIVA21 5-Stage RO: No. VIVA21 6-Stage Alkaline RO: Yes.
Which system has the lower MSRP?
VIVA21 5-Stage RO has the lower MSRP in the current SLF records at $289.99, compared with $339.99 for the other system.
Do both systems require a plumbing connection?
VIVA21 5-Stage RO: Yes. VIVA21 6-Stage Alkaline RO: Yes.
Which system is more renter friendly?
VIVA21 5-Stage RO: No. VIVA21 6-Stage Alkaline RO: No. Check lease and plumbing-modification rules before installing an under-sink system.
What certifications are listed for these systems?
VIVA21 5-Stage RO: Filter United identifies exact model V21RS5S01 as WQA Gold Seal certified to NSF/ANSI 58 for reverse-osmosis system performance and NSF/ANSI/CAN 372 for lead-content compliance. SLF has not independently located the exact model in WQA's searchable public directory, so retain the manufacturer-source qualification until the directory record is captured. VIVA21 6-Stage Alkaline RO: Manufacturer states VIVA21 6-Stage Alkaline RO (V21RS6S01PH) is WQA Gold Seal certified to NSF/ANSI 58 for RO system performance and NSF/ANSI 372 for lead-free materials. WQA Gold Seal is third-party product certification. SLF has not independently confirmed the exact model in WQA's public certified-product directory; retain manufacturer-source qualification pending direct directory verification.
How do estimated annual filter costs compare?
VIVA21 5-Stage RO: $60.00. VIVA21 6-Stage Alkaline RO: $60.00. Actual replacement timing and prices can vary.