Filter United VIVA21, 6-Stage Alkaline Reverse Osmosis System

Lifespan Vault earns an affiliate commission when you buy through links on this page, at no extra cost to you. It does not change our rankings or our verdicts.

An under-sink reverse osmosis system at $249.99 with a sixth alkaline remineralization stage, rated 50 GPD at 60 psi, that Filter United says installs in about 30 minutes with basic tools.

The VIVA21 6-stage is a non-electric under-sink reverse osmosis system. Water runs through a 5-micron sediment filter, two 5-micron extruded carbon blocks, a 50 GPD high-rejection TFC reverse osmosis membrane, a coconut shell post-carbon filter, and a sixth alkaline remineralization stage that Filter United says restores essential minerals and raises pH. It is rated at 50 GPD at 60 psi and wants feed pressure between 40 and 80 psi and feed water between 40 and 100 Fahrenheit. The unit measures 16"W x 6"D x 18"H, the 4-gallon tank is 11"W x 11"D x 15"H, and the box ships with the faucet, the tank, a leak stop valve, and the components for a standard install. Filter United puts that install at about 30 minutes with basic tools and color-coded tubing. Running cost is published rather than hidden: the brand states most households spend roughly $40 to $80 a year, with sediment and carbon swapped about every 12 months and the membrane and inline carbon every 2 to 3 years. The complete 6-stage cartridge set is $99.99. No subscription is required to buy it; autoship is an optional program at 15% off filters.

Where it gives ground, and it gives more than the price suggests. Filter United states the system is WQA Gold Seal certified to NSF 58 and NSF 372, but publishes no certificate number, no listing link, and no per-contaminant performance data sheet, and we could not confirm the listing with a third party, so treat the certification as the brand's claim rather than a verified one. The site's headline contaminant-removal figure is unquantified and its own FAQ walks it back to reductions "up to certain levels" with additional media possibly required, so we do not repeat it. The warranty copy contradicts itself on the same page: the bullets say lifetime limited parts while the warranty section says a 1-year manufacturer limited warranty plus one extra year if you register within 90 days. Two years is the specific figure, so that is the one we card. The on-page rating distribution is 167 five-star reviews and literally nothing below five, which is a pattern we will not cite as proof. And the brand publishes no founding year, no office address, and no team page, so there is not much provenance to lean on. The alkaline pH stage is a taste and mineral feature; we attach no health claims to it.

This suits a homeowner on municipal water who wants reverse osmosis plus remineralization at the kitchen tap for under $250, has cabinet room for a 16 by 18 inch unit and a 4-gallon tank, and is comfortable buying on published specs and a brand-stated certification. Filter United is a US company that says the VIVA21 is designed and assembled in California and ships from Southern California. The identical 5-stage version is $199.99 and is the same system minus the alkaline stage, so the sixth stage costs $50, which is roughly what the alkaline cartridge alone runs at $49.99.

Specifications