Frequently asked questions
Where does ZIP Water Report’s data come from?
Two public EPA datasets: the Safe Drinking Water Information System (SDWIS), which records every violation reported by public water systems, and UCMR 5, the EPA’s 2023–2025 national PFAS testing program. We refresh the data quarterly. We do not test water ourselves.
What does my grade mean?
Every water system starts at 100 points. Health-based violations in the last 5 years weigh heaviest, monitoring and paperwork lapses count a little, and PFAS results are compared against the 2024 federal limits. A = excellent through F = failing. The full formula is on the methodology page.
Why isn’t my ZIP code listed?
We map water systems to the ZIP codes they report serving. Some utilities report only their main office ZIP, so your neighborhood may be grouped under a neighboring ZIP — the search box suggests nearby covered ZIPs automatically. Private wells are not covered at all: the EPA only regulates public water systems.
My water got a C, D or F. Is it unsafe to drink?
Not necessarily. A grade is our summary of federal compliance records, not a health determination. A low grade means the system has recent violations or PFAS detections worth reading about. Check the violations listed on your ZIP’s page, read your utility’s annual Consumer Confidence Report, and contact the utility with questions.
What are PFAS and why do they matter?
PFAS (“forever chemicals”) are synthetic compounds that persist in water and in the body. In 2024 the EPA set the first enforceable drinking-water limits: 4 parts per trillion for PFOA and PFOS, 10 ppt for PFHxS, PFNA and GenX. We flag any system whose UCMR 5 tests detected PFAS, and weigh results above the limits heavily in the grade.
The data for my water system looks wrong or outdated.
Our copy of the EPA records can lag official sources by up to a quarter, and utilities sometimes correct records after the fact. The authoritative source is your utility’s Consumer Confidence Report and the EPA’s own SDWIS search. If a violation was resolved, it still counts toward the 5-year history — that is by design.
Does a good grade mean I don’t need a water filter?
A grade reflects the water system’s federal compliance, not what happens between the treatment plant and your tap — old building pipes, lead service lines and private plumbing are not in this data. If you want certainty about your own tap, a certified home test is the only way to know.
Something else? The methodology page explains exactly how grades are computed.