Lead and Copper Rule — what the rule requires, clause by clause.
The Lead and Copper Rule (LCR) and Lead and Copper Rule Improvements (LCRI) live in 40 CFR 141 Subpart I (§§ 141.80–141.93). This reference maps every clause to the authoritative eCFR text. 1water.ai’s compliance validator computes the § 141.80(c)(3) 90th-percentile calculation with a full audit trail.
Verified against eCFR on 2026-04-18.
Every value below is sourced from the eCFR snapshot and the Federal Register. We do not publish MCL, action level, or effective-date numbers from memory. Click through for the authoritative text.
Every clause in 40 CFR 141 Subpart I.
Each card links to the authoritative eCFR page. Regulation text is never paraphrased on 1water.ai — when a section requires inline quotes, they come frompackages/reference/verbatim-blocks.ts, populated via the eCFR JSON API.
General requirements and action level
The anchor section. Lead action level is 0.010 mg/L (10 ppb) under LCRI (§ 141.80(c)(1)); copper action level is 1.3 mg/L (§ 141.80(c)(2)). The 90th-percentile calculation method is defined in § 141.80(c)(3).
Read on eCFR →Applicability of corrosion control treatment steps
Corrosion control obligations by system size. § 141.81(a)(4)(i) defines the transition window between the 2020 LCR codification and LCRI: October 30, 2024 – November 1, 2027.
Read on eCFR →Description of corrosion control treatment requirements
Detailed treatment-technique requirements for optimizing corrosion control: study design, state approval, water-quality parameter maintenance.
Read on eCFR →Source water treatment requirements
Triggered when action level exceedance persists despite corrosion control. Requires source-water study and possible treatment.
Read on eCFR →Service line inventory and replacement requirements
Every community water system must maintain a service-line inventory and replace lead and galvanized-requiring-replacement (GRR) service lines. Inventory deadlines, replacement rates, and customer-side notification live here.
Read on eCFR →Public education and supplemental monitoring and mitigation
Public education content and timing after a lead action level exceedance, plus supplemental filters-and-flushing programs. Ties directly to CCR § 141.154 triggered content.
Read on eCFR →Monitoring requirements for lead and copper in tap water
Site tier selection (Tier 1–5), first-liter and fifth-liter sampling protocols, sampling-period frequencies, and the pool of eligible samples that feeds the 90th-percentile calculation in § 141.80(c)(3).
Read on eCFR →Monitoring requirements for water quality parameters
Water-quality-parameter monitoring that supports corrosion control optimization — pH, alkalinity, calcium, conductivity, orthophosphate, silica, temperature.
Read on eCFR →Monitoring requirements for lead and copper in source water
Source-water monitoring once a system is on an approved source-water treatment plan under § 141.83.
Read on eCFR →Analytical methods
Approved laboratory methods for lead, copper, and water-quality-parameter analyses. Detection-limit thresholds that affect reporting.
Read on eCFR →Reporting requirements
What the system must report to the primacy agency and by when. Deadlines for sampling results, corrosion-control recommendations, public-education certifications, and service-line inventory updates.
Read on eCFR →Recordkeeping requirements
Retention periods for LCR records. Sampling records, corrosion-control studies, water-quality-parameter data, and service-line inventory documentation.
Read on eCFR →Monitoring for lead in schools and child care facilities
Supply-side monitoring at schools and licensed child care facilities served by community water systems. Compliance schedules and outreach requirements.
Read on eCFR →Small water system compliance flexibility
Alternative compliance pathways for small systems that cannot feasibly apply standard corrosion control or full replacement within the LCRI timeframe.
Read on eCFR →CCR Lead & Copper narrative.
Every Consumer Confidence Report that reports lead or copper tap-water data must include the Lead & Copper narrative required by 40 CFR § 141.153(d)(4) and — when the lead action level is exceeded — the educational language required by § 141.154. See our Consumer Confidence Report guide for the section-by-section walkthrough, or start drafting on the CCR Agent.
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