How we evaluate water filters
Countertop Filter exists because water filtration has a paperwork problem: the same box can say 'NSF' for three very different levels of proof. Our job is to sort them, in public, product by product.
Who this site is for
Shoppers in the United States. Prices are US dollars from US retailers; the rules we cite are US rules (EPA drinking-water standards, NSF/ANSI certifications); the dealer networks, installed-cost data and well-water guidance are US-specific. Readers elsewhere will find the certification explainers useful, but should check their own country's standards and pricing.
Our rules
- Certification first. Products are graded certified / third-party tested / no system certification, based on the manufacturer's own wording and certifier listings - and we quote the wording rather than paraphrasing it into something stronger.
- Claims belong to their makers. Reduction percentages on this site are the manufacturer's or its named lab's, always attributed. We don't run a lab and we don't invent numbers to fill a table.
- Prices are checked, dated, and re-checked. Every price carries the date we verified it against the manufacturer or a named source. Prices move; the date tells you how much to trust the figure.
- Running costs count. A $70 filter that eats $150 a year in cartridges is not cheaper than a $400 system that sips. Our rankings and calculator use total cost, not sticker price.
- Corrections are part of the product. When a model is discontinued (Waterdrop's K19-S, ProOne's Big+) or a brand's paperwork contradicts itself, the page says so.
How the site makes money
Some links are affiliate links: if you buy through them, we may earn a commission from the retailer at no extra cost to you. That revenue funds the checking and re-checking above. It never buys a better grade - several of our top-ranked products are sold by brands with no affiliate relationship with us at all, and our certification badges follow the paperwork wherever it leads.
What we are not
We are not a water-testing laboratory, a plumbing company, or a substitute for your water utility's reports and your own lab tests. Start with the facts about your water - here's how - and let treatment follow diagnosis.