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How to Read Your Water Quality Report

How to read your water quality report: your CCR shows treatment plant averages, not your tap. Here is what the numbers actually mean and what to test yourself.

The Consumer Confidence Report: What It Shows and What It Misses

Every community water system in the US serving more than 25 people must publish an annual Consumer Confidence Report (CCR). It reports detected contaminant levels, legal limits, the source of your water, and any violations from the previous calendar year. The CCR is useful, legally required, and the correct first step when evaluating your water quality.

Its limitations are structural and important to understand. The CCR reports utility testing data — samples collected at the treatment plant exit or distribution system sample points. It does not represent your specific tap. It tests the water after treatment and before it enters your home's plumbing. Lead, which enters water from your household pipes and service line rather than the treatment plant, may show differently at your tap than in utility testing.

Decoding the Numbers in Your CCR

Maximum Contaminant Level (MCL)

What it is: The legally enforceable limit for a contaminant in drinking water
Example: Lead action level: 15 ppb. If 10% of utility samples exceed this, action is required.
Note: MCLs are set based on health risks AND technical/economic feasibility. Many MCLs are higher than health-based goals.

Maximum Contaminant Level Goal (MCLG)

What it is: The concentration at which no known health effects occur — the true health target
Example: Lead MCLG: zero. Arsenic MCLG: zero. Any lead or arsenic detection represents some health concern.
Note: MCLGs are health goals, not enforceable limits. Water can be legally compliant but above the MCLG.

Range (Low-High) / Average

What it is: Detected concentrations throughout the year or across the distribution system
Example: A range of 0.001–0.008 mg/L for a contaminant with a 0.010 MCL means all samples were within the legal limit.
Note: The range matters. If your sampling point is typically higher than average, your tap may see levels at the high end of the range.

Treatment Technique (TT)

What it is: A process requirement the utility must follow when there is no practical MCL
Example: Lead and copper: instead of an MCL, utilities must follow the Lead and Copper Rule — corrosion control treatment, monitoring, service line replacement.
Note: Treatment technique violations mean the process was not followed, not necessarily that a concentration was exceeded.

Violation

What it is: Any departure from the EPA requirements in that reporting year
Example: A monitoring violation means the utility failed to test as required. A health standard violation means detected levels exceeded MCLs.
Note: All violations must be disclosed in the CCR. Any health standard violation should prompt your own tap testing.

After Reading Your CCR: What Actions to Take

Any violation in your CCR

High

Order a Tap Score Essential City test ($179) immediately. Violations indicate the utility failed to meet requirements — understand the specific contaminant and your household exposure.

Lead detected at any level; home built before 1986

High

Test your specific tap for first-draw lead. Utility testing and household plumbing lead are independent. A filter (NSF 53-certified) is warranted for pre-1986 homes regardless of CCR data.

PFAS detected at or near 4 ppt action level

High

Order Tap Score Advanced City ($289) for a complete PFAS panel. Install an NSF P473-certified filter (Clearly Filtered, AquaTru) while results are pending.

Contaminants present but well below MCLs, no violations

Normal

Your city water is legally compliant. Consider testing your specific tap for lead if your home has old plumbing. An NSF 42/53-certified under-sink filter for taste and lead is prudent for most households.

Cross-Reference With EWG: They Show Health Guidelines, Not Just Legal Limits

The EWG Tap Water Database (ewg.org/tapwater) runs your utility CCR data through health-based limits that are more protective than EPA MCLs. A contaminant may be legal but shown as a concern on EWG because the MCL is above the health guideline. This is not alarmism — it is a more protective analysis. Use EWG data to identify contaminants to add to your lab test panel, not to panic about your water.

Recommended Test Kits

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Tap Score Well Water Test

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Frequently Asked Questions