How we research

GudWater exists to help people buy the right water filter for the water they actually have. This page explains how we work so you can decide how much to trust us.

Sources we rely on

• Regulators: US EPA drinking water regulations and fact sheets, the CDC, and state drinking water programs.
• Standards bodies: NSF International and ANSI standards, and the public certification listings from NSF, IAPMO, WQA and other accredited certifiers.
• International guidance: World Health Organization Guidelines for Drinking-water Quality.
• Peer-reviewed research: we link to the original study, not a press release, whenever we can.

Rules we follow

• We never say a filter removes a contaminant unless it is certified to reduce it or an independent lab report shows it.
• We don't repeat health claims that human studies don't support, even when they are popular.
• Every guide lists its sources and the date we last reviewed it. When EPA rules change, we update the affected guides.
• Brands cannot pay for placement or for a better verdict.

How GudWater makes money

Some links may be affiliate links. If you buy through one, we may earn a commission at no extra cost to you. It never changes what we recommend. Read the full affiliate disclosure.

Corrections

If you spot an error, tell us. We fix factual errors quickly and note significant corrections at the end of the guide.