Every community water system in the United States must give its customers a water quality report each year. It is often called a Consumer Confidence Report, or CCR, and it is one of the most useful documents you can read about your drinking water.
Where to find it. Most utilities post the report on their website and mention it on your water bill. New York City publishes its Drinking Water Supply and Quality Report online every year. If you rent, your landlord may not pass it along, so look it up directly.
Start with the source. The first pages usually describe where your water comes from and how it is treated. This tells you a lot: surface water and groundwater have different typical concerns.
Then read the table. The heart of the report is a table of detected contaminants. For each one you will usually see the legal limit (MCL), the health goal (MCLG), the level detected and whether the system was in compliance. Pay attention to the range as well as the average.
Lead and copper are reported differently. Instead of an average, you will usually see the 90th percentile result from homes the utility sampled, and how many homes exceeded the action level. These samples come from customer taps, so they reflect plumbing as well as the water supply.
What the report cannot tell you. The report describes the water system as a whole. It does not tell you what comes out of your faucet, which depends on your own service line and plumbing. If your building is older or something has changed, testing your own tap is the only way to know.
