How We Test Water Filters

Last updated August 2026

Every recommendation on Filter Tested is grounded in the same evaluation framework, so you can compare systems fairly.

What we measure

• Contaminant reduction — what a system is certified or independently shown to reduce (lead, chlorine, fluoride, arsenic, PFAS, sediment, hardness), and against which NSF/ANSI standards where applicable.
• Flow rate and capacity — real gallons-per-minute and filter life, because a filter that chokes your water pressure or needs constant replacement is not a bargain.
• Installation and maintenance — how hard it is to install, and the true ongoing cost of replacement filters or salt.
• Value — total cost of ownership over several years, not just the sticker price.

Honesty first

We do not present manufacturer specs as our own lab measurements. Where we cite reduction figures, they come from certifications or published testing; everything else is framed as expert buying guidance. We name what each product does well and where it falls short, and we recommend skipping products that do not earn their price.