Water
Water is a chemistry problem.
Your utility treats one supply for a whole city and reports an average. What reaches your tap depends on your pipes, your fixtures, your address. These are the contaminants we grade, each against two lines: the legal limit and the level the health research calls safe.
On every row the legal limit sits where the city is allowed to leave it. The health research draws the line somewhere else. That distance is what we grade.
Is my tap water actually safe?
For the most part, yes. If you're on a public water system, your utility keeps it free of the germs that used to kill people, and that achievement holds. But legal and ideal are two different standards, and what reaches your glass also depends on your own pipes and your local source water. The honest answer for your house starts with a test.
The risks worth taking seriously
The dangers that made water famous, cholera and typhoid, were solved a century ago by disinfection, and that fix still works. Today's concerns are quieter. Lead from old plumbing can affect a child's developing brain, and health agencies have concluded there is no level of it known to be safe. Forever chemicals (PFAS, long-lasting industrial compounds) build up in the body over years, and nearly every American adult already carries some in their blood. And the chlorine that protects water on its way to you leaves behind byproducts that research links to higher cancer risk over long-term exposure. None of these have a taste or a smell. They work on the timescale of years of ordinary glasses of water, which is exactly why they are easy to ignore and worth taking seriously.
How it gets into your water
There are two doors. The first is the water itself. Forever chemicals arrive with the source water, in the rivers, wells, and reservoirs your utility draws from, so your level depends on where your water starts, and you cannot tell by looking. Disinfection byproducts form along the way, when chlorine reacts with natural organic matter in the water, so if your supply is chlorinated, and almost all municipal water is, some amount reaches every tap. The second door is your own house. Lead is usually a house problem. It dissolves into water that sits in contact with older plumbing: pipe solder used before 1986, brass fittings made before 2014, and, in some older cities, the service line connecting your house to the main. Your utility's report can be spotless and still say nothing about that last stretch, because its responsibility ends at the curb. For lead, the age of your home matters more than your zip code.
What you can do about it
Start by finding out what is in your water, because the right fix depends on the finding. Your utility publishes a water quality report every year, and it is worth reading, but it describes the system as a whole and stops before your plumbing. A test from your own tap is the only measurement that includes your house. Once you know what you are dealing with, the fixes are ordinary and within reach. Different filters do different jobs: a simple carbon filter handles chlorine byproducts and taste, while removing forever chemicals or lead calls for a filter certified for that specific job, often a reverse osmosis system (one that forces water through an extremely fine membrane). No single filter removes everything, and you should not need everything. Test first, fix what shows up, and skip what does not.
The reference shelf
Every entry we grade against, in the scientific detail. Each one answers first, then shows its receipts.
Where the legal limit lags the health line
Where there is no limit to hold to
Where the line is comfort, not health
Curious what is actually in your water?
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