The Nerd Stamp™ Methodology

The Nerd Stamp rates every product in this index from 1 to 7 across seven verifiable criteria. One point per criterion. No partial credit. No points for design, brand reputation, or unverifiable claims. If a specification cannot be confirmed in manufacturer documentation or a certification listing, it does not score.

The seven criteria: (1) certified removal scope, meaning the specific NSF/ANSI standards the unit holds, 42, 53, 58, 401, or P473, and the contaminants those standards cover; (2) certification and test transparency, meaning a published NSF or WQA listing number, a stated micron rating, and documented test data; (3) filter life and rated capacity in gallons or months; (4) cost per gallon, calculated from cartridge price divided by rated capacity; (5) flow rate and pressure drop; (6) install and footprint, including whether the unit needs plumbing, tools, or permanent modification; (7) maintenance burden, meaning filter changes per year and whether cartridges are standard or proprietary.

CostPerGallon is the second axis: verified removal per dollar. Two units can both score 7 of 7 while one costs materially less to run. The cheaper 7 of 7 wins. This is why a pitcher with a published NSF 53 listing can outrank a system costing several times as much with no certification record.

Scores change when specifications change. A discontinued certification, a revised cartridge, or corrected documentation triggers a rescore and an updated revision date on the review.

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