SLF Water Filtration Comparison · 2026
VIVA21 6-Stage Alkaline RO
Recommended
Waterdrop X8
A strong premium choice for families that want 800 GPD tankless RO performance, robust certification, and smart TDS monitoring without stepping up to the much more expensive X12 or X16.
Waterdrop X8
Choose the X8 when you want premium certification and smart monitoring at 800 GPD but do not need alkaline remineralization.
RO Performance & Ownership
Compare RO output, filtration stages, remineralization, contaminant evidence, certifications and ownership cost.
Which Is Right for You?
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
Waterdrop X8
Best for: Families and higher-use households wanting certified tankless RO filtration with 800 GPD output and smart TDS monitoring.
Consider if: Want TDS Display
Our Recommendation
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.
Waterdrop X8
The Waterdrop X8 is best for households wanting a premium but not flagship-priced tankless RO system. Its 800 GPD output, smart TDS faucet and NSF/ANSI 42/58/372 certification make it a strong step up from Waterdrop's value-oriented G-series.
The Short Answer
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.
Choose the X8 when you want premium certification and smart monitoring at 800 GPD but do not need alkaline remineralization.
Water Filter Comparison FAQs
Answers are generated from the current SLF product records for these two systems.
Which is better, VIVA21 6-Stage Alkaline RO or Waterdrop X8?
Waterdrop X8 is the overall pick for this specific matchup. Choose the X8 when you want premium certification and smart monitoring at 800 GPD but do not need alkaline remineralization.
Which system has the higher daily filtration capacity?
Waterdrop X8 has the higher rated output: 800 GPD versus 50 GPD.
Which system offers remineralization?
VIVA21 6-Stage Alkaline RO: Yes. Waterdrop X8: No.
Which system has the lower MSRP?
VIVA21 6-Stage Alkaline RO has the lower MSRP in the current SLF records at $339.99, compared with $799.00 for the other system.
Do both systems require a plumbing connection?
VIVA21 6-Stage Alkaline RO: Yes. Waterdrop X8: Yes.
Which system is more renter friendly?
VIVA21 6-Stage Alkaline RO: No. Waterdrop X8: No. Check lease and plumbing-modification rules before installing an under-sink system.
What certifications are listed for these systems?
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. Waterdrop X8: Waterdrop states the X8 system is certified by IAPMO R&T against NSF/ANSI 42 and 58 for reduction claims specified on the Performance Data Sheet and to NSF/ANSI 372 for low lead.
How do estimated annual filter costs compare?
VIVA21 6-Stage Alkaline RO: $60.00. Waterdrop X8: $161.97. Actual replacement timing and prices can vary.