Plain answers, each from the public data behind the Water Scores.
These answers cover how the Water Score works, where the data comes from and what a published health guideline is. Each county, city, utility and ZIP code page adds its own questions, answered from its own data (291 ZIP codes in 3 counties).
A Water Score from 0 to 100 for each ZIP code, built from public test results of the utility that serves it. The Florida data covers 291 scored ZIP codes in Miami-Dade, Broward and Palm Beach, plus 64 cities and 114 water utilities statewide.
EPA SDWA, EPA UCMR and Florida DEP data for test results, EPA Water System Boundaries (CWS service area boundaries) v3.0, March 2026 release to match ZIP codes to utilities, and published health guidelines from California OEHHA (public health goals) and the U.S. EPA (the PFBS health advisory), with EPA maximum contaminant levels and action levels as legal limits. Every source and the years covered are listed on the sources page.
The score starts at 100. It goes down 8 for each contaminant above a cited health guideline whose source states a cancer basis, 5 for each other contaminant above its cited guideline, 5 for each of PFOA and PFOS averaging above the 4.0 ppt limit in EPA's 2024 PFAS rule, 10 for each contaminant whose average of all samples is above EPA's legal limit (instead of its guideline step), and 1 for each contaminant with a cited cancer-based guideline that is detected below it. Only guidelines with a cited document count. The lowest score is 5. Higher is better.
A legal limit is an enforceable standard, set by the EPA under the Safe Drinking Water Act. Limits weigh health research together with the cost and feasibility of treatment. A health guideline is published by public-health sources and based on health research alone. A utility can meet every legal limit and still be above a published health guideline.
Arsenic (above its guideline in 27 utilities, up to 480 times), Bromodichloromethane (above its guideline in 12 utilities, up to 277 times) and Dibromochloromethane (above its guideline in 12 utilities, up to 125 times). Source: EPA SDWA, EPA UCMR and Florida DEP data, 2015-2026.
Chloramine is a disinfectant made by combining chlorine and ammonia. Some water systems use it in place of free chlorine. The public data used on this site does not record which disinfectant each utility uses, so we do not say. Your utility can tell you.
The pages are generated from the data, and they update automatically when new or additional data arrives. Each page shows the date its data last changed. The EPA compliance records come from the July to September 2026 extract. Data may be one to three years old and may not reflect water at your tap.
Our claims cover three results: chlorine and hardness at your kitchen tap, and dissolved solids at your drinking-water faucet. Guarantee terms ›