Blog

Writing about what's in American tap water

Explainers built on the federal testing record rather than on press releases. Every figure we publish is traceable to a dataset you can download and check yourself.

Water safety

Water safetyStart here

Is tap water safe to drink in the US?

We processed all 1,992,002 federal test results and found something nobody expects: larger water systems tested worse than smaller ones.

12 min read Water safety

Is bottled water safer than tap water?

Two different agencies, two different rulebooks, and a price difference that is easy to underestimate by a factor of a hundred.

8 min read

Contaminants

What PFAS are, and how they got into drinking water

A class of chemicals invented to be indestructible, used for eighty years, and now present in the water supplied to a majority of tested American water systems.

9 min read Contaminants

Lead in drinking water: why the pipe matters more than the plant

Every other contaminant on this site is a question about your water system. Lead is a question about your house.

8 min read Contaminants

Chlorine and chloramine: the trade-off that makes water safe

Chlorination is why waterborne typhoid vanished from American cities. It also creates by-products that are themselves regulated. Both things are true.

7 min read Contaminants

Fluoride in US tap water, and who decides

Fluoridation is decided locally, not nationally, which is why the answer for your neighbor's town may differ from yours.

7 min read

Problems you can see

Why your tap water looks cloudy or milky

There is a simple test that separates the harmless explanation from the ones worth acting on, and it takes about two minutes.

6 min read Problems you can see

Why tap water smells like bleach, sulfur or sewage

Smell is the most useful sense you have for tap water, because different causes produce recognizably different smells.

7 min read

Testing

How to read your annual water quality report

Every community water system in the country publishes one of these each year. Almost nobody reads it, largely because the table is written for regulators.

8 min read

Filters and treatment

Which filters actually remove PFAS

Most filters sold in American supermarkets do nothing whatsoever about PFAS. The ones that work say so in a specific, checkable way.

8 min read

Or skip the reading and check your own water

Check your ZIP code