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Water Quality Reference Guides

Water quality involves a lot of acronyms and overlapping standards. EPA limits, NSF certifications, and utility reports all measure different things in different ways.

The guides here translate those systems into plain language. No jargon. Just what you need to make a good decision.

Start with your water quality report if you have city water, your utility sends one every year and most people never read it. If you have a private well, start with the EPA and NSF explainers, which will help you understand what your test results mean and what certification to look for in treatment equipment.

Water Quality by State and Region

Water quality issues vary significantly by location. Well water in New England has different risks than municipal water in Texas. These guides focus on what’s most relevant in each area.

Reference Guides

How to Read Your Water Quality Report

Your utility sends a Consumer Confidence Report every year. Most people don't know what's in it. Here's how to read it.

EPA MCL vs. MCLG Explained

Legal limits and health-based limits are different numbers. Understanding why matters when you read contamination test results.

NSF Certification Standards Explained

NSF 42, 53, 58, 401, what each certification actually covers and why it matters when choosing a water filter.

Tap Water for Baby Formula

Lead, nitrates, and bacteria are the three risks worth checking before mixing formula.

Drinking Water During Pregnancy

Lead, PFAS, and nitrates have real pregnancy research behind them. Here's what it shows.

Water Safety for Pets

Tap, filtered, distilled, or bottled? What's actually safe for dogs and cats.

Distilled Water for CPAP and Humidifiers

Why CPAP manufacturers require distilled water and what happens if you don't use it.

Drinking Water with Kidney Disease

Potassium, phosphorus, and sodium in tap water. What kidney patients actually need to know.

Does Boiling Water Remove Contaminants?

It kills bacteria and viruses. It doesn't remove lead, nitrates, PFAS, or most chemicals.

EPA PFAS Drinking Water Rule 2024

What the new 4 ppt limits mean, which utilities must comply, and when.

States Reducing Fluoride in Water

Which states have restricted fluoridation in 2025 and 2026, and what evidence drove it.

Water for Aquariums and Fish Tanks

Tap water contains chlorine and chloramines that kill fish. What to do before adding water to a tank.

Distilled vs. Filtered Water for Humidifiers

Tap water in a humidifier disperses minerals as white dust. Distilled water is the standard recommendation.

Frequently Asked Questions

What is a Consumer Confidence Report?
A Consumer Confidence Report (CCR) is an annual water quality report that public water utilities in the US are required to send to customers. It lists the contaminants tested, their measured levels, and the EPA limits that apply. Private well owners don't receive CCRs, they're responsible for testing their own water.
What does EPA MCL mean?
MCL stands for Maximum Contaminant Level, the highest amount of a contaminant that is legally allowed in public drinking water. MCLs are set through a regulatory process that weighs health risk against what treatment technology can reliably achieve and what it costs. They are not the same as health-based limits.
What is NSF certification for water filters?
NSF International is an independent testing organization that certifies water treatment products. Different NSF standards cover different contaminants. NSF 42 covers taste and odor. NSF 53 covers health-effect contaminants like lead. NSF 58 covers reverse osmosis systems. A filter certified under one standard is not automatically certified under others.