Frequently Asked Questions

Most U.S. tap water meets EPA legal standards — but "meeting standards" is not the same as being free of contaminants. EPA limits are set based on what's technically and economically feasible to achieve, not always what's safest for health. The EPA's own Maximum Contaminant Level Goals (MCLGs), which represent the health-ideal level, are often zero for the same contaminants that have a non-zero legal limit. Independent organizations like the Environmental Working Group (EWG) regularly find contaminants in compliant tap water at levels above what independent health scientists consider safe. Enter your ZIP code on our home page to see exactly what EPA data shows for your water system.

Carbon filters (activated carbon or carbon block) work by adsorption — contaminants stick to the surface of the carbon as water flows through. They are excellent at removing chlorine, chloramine, VOCs, taste, odor, and some heavy metals. However, they cannot remove nitrates, fluoride, most PFAS, TDS, or dissolved minerals. Reverse Osmosis (RO) forces water through a semi-permeable membrane with pores so small (0.0001 microns) that only water molecules pass through. RO removes 95–99%+ of virtually all dissolved contaminants including lead, arsenic, nitrates, fluoride, PFAS, TDS, bacteria, and more. RO systems are the gold standard for comprehensive drinking water purification.

PFAS (Per- and Polyfluoroalkyl Substances) are a group of over 12,000 man-made chemicals used in non-stick cookware (Teflon), firefighting foam, food packaging, stain-resistant fabrics, and industrial processes since the 1940s. They are called "forever chemicals" because the carbon-fluorine bond — one of the strongest in chemistry — never breaks down in the environment or the human body. PFAS accumulate in your body over time. Health effects include kidney and testicular cancer, thyroid disruption, immune suppression (including reduced vaccine effectiveness), high cholesterol, and developmental problems in children. In 2024, the EPA set the first-ever enforceable limit for PFAS in drinking water at 4 parts per trillion. Standard carbon pitcher filters do NOT effectively remove PFAS — you need a reverse osmosis system or a specifically PFAS-certified activated carbon system.

WaterCheckup pulls from six authoritative data sources — five from the EPA and one from the Environmental Working Group (EWG). (1) EPA Violation Records — live violation history and system data for 150,000+ public water systems via the EPA Envirofacts API. (2) EPA PFAS Testing Data — federal PFAS monitoring results from 2023–2025 covering 6,151 water systems, the most comprehensive PFAS dataset ever collected. (3) EPA Enforcement History — inspection records, formal actions, and penalty data from the EPA enforcement database. (4) EPA Lead Tap Sampling — actual measured lead levels at the tap from EPA Lead & Copper Rule testing. (5) EPA Lead Pipe Inventory — federal lead service line inventory data, which all US utilities were required to publish as of October 2024. (6) EWG Health Guidelines — the Environmental Working Group's independent health benchmarks, which are stricter than EPA legal limits and used to flag contaminants that are legal but still a concern. Your ZIP code is matched to your specific water system and all available data is combined into a single free report.