The Lead and Copper Rule is the US drinking-water regulation in 40 CFR 141 subpart I that sets a lead action level of 0.010 mg/L and a copper action level of 1.3 mg/L at the 90th percentile of tap samples, with LCRI compliance from 2027-11-01. Three editions shape it, the 1991 LCR, the 2021 LCRR and the 2024 LCRI, so which requirements reach the chemicals a water system doses?
Its corrosion control and water quality parameters decide which water treatment chemicals a utility doses, from pH adjusters to orthophosphate and silicate inhibitors, and how the utility proves the dose works.
The 6 key figures are listed below.
- Lead action level: 0.010 mg/L (10 µg/L) from 2027-11-01; 0.015 mg/L until then.
- Copper action level: 1.3 mg/L.
- Minimum distribution pH: 7.0, where State-designated.
- Minimum tap orthophosphate: 0.5 or 1.0 mg/L as PO4, where State-designated.
- Lead service lines: replaced within 10 years.
- LCRI compliance date: 2027-11-01.
Every value on this page is checked against the eCFR, the Federal Register and EPA rule pages; see our methodology and fact-checking process. This page summarizes the rule text and is not legal advice; the State primacy agency sets system-specific requirements.
What Is the Lead and Copper Rule?#
The Lead and Copper Rule is a National Primary Drinking Water Regulation that controls lead and copper at consumers' taps through a treatment technique, corrosion control, triggered by action levels rather than by a maximum contaminant level. EPA issues it under the Safe Drinking Water Act (Public Law 93-523, 1974-12-16) and codifies it in 40 CFR 141.80 to 141.93.
LCR, LCRR and LCRI: How the Three Editions Differ#
The Lead and Copper Rule has 3 editions: the original LCR of 1991, the Lead and Copper Rule Revisions (LCRR, 86 FR 4198, 2021-01-15) and the Lead and Copper Rule Improvements (LCRI, 89 FR 86418, 2024-10-30). The table below compares them.
| Edition | Federal Register | Date | Lead action level | Key change for water systems |
|---|---|---|---|---|
| LCR (original rule) | published 1991-06-07 | 1991-06-07 | 0.015 mg/L | lead and copper action levels (90th percentile); corrosion control treatment |
| LCRR (Lead and Copper Rule Revisions) | 86 FR 4198; delay rule 86 FR 31939 | 2021-01-15; 2021-06-16 | 0.015 mg/L | lead service line inventory; trigger level; inventory and notification provisions from 2024-10-16 |
| LCRI (Lead and Copper Rule Improvements) | 89 FR 86418 (FR doc 2024-23549) | published 2024-10-30; effective 2024-12-30; compliance 2027-11-01 | 0.010 mg/L from 2027-11-01 | lower lead action level; trigger level replaced; minimum pH and orthophosphate; 10-year lead service line replacement |
The LCRR added the lead service line inventory and a trigger level, with inventory and notification provisions from 2024-10-16; the LCRI replaced the trigger level.
Who Must Comply with the Lead and Copper Rule?#
Community water systems (CWS) and non-transient non-community water systems (NTNCWS) must comply with the Lead and Copper Rule, and LCRI sets their compliance date at 2027-11-01 (40 CFR 141.80(a)). Large systems serve more than 50,000 people and medium systems more than 10,000 to 50,000 (40 CFR 141.81). States with primacy adopt the rule, designate each system's corrosion control parameters and review its reports.
Which Lead and Copper Rule Requirements Affect Treatment Chemicals?#
Five Lead and Copper Rule requirements affect treatment chemicals: the action levels, optimal corrosion control treatment, optimal water quality parameters, tap and water quality parameter sampling, and lead service line replacement.
Lead and Copper Action Levels (90th Percentile)#
The lead action level is 0.010 mg/L (10 µg/L, 10 ppb) and the copper action level is 1.3 mg/L, each exceeded when the 90th percentile of tap samples is above the value (40 CFR 141.80(c), as amended by LCRI).
Until 2027-11-01, systems follow subpart I as codified on 2020-07-01, with the 0.015 mg/L lead action level, plus listed LCRR inventory and notification provisions (40 CFR 141.80(a)(4)). The 1.0 mg/L copper value in 40 CFR 143.3 is a non-enforceable secondary standard, not the action level.
Optimal Corrosion Control Treatment (OCCT): pH, Alkalinity and Inhibitors#
Optimal corrosion control treatment under 40 CFR 141.82(c) is chosen from alkalinity and pH adjustment, listed first, and an orthophosphate- or silicate-based corrosion inhibitor, with orthophosphate tested at 1 and 3 mg/L as PO4 in study samples.
A lead 90th percentile above the 0.005 mg/L practical quantitation limit triggers an OCCT study for large systems without corrosion control treatment (40 CFR 141.81). Alkalinity and pH adjustment uses caustic soda, lime, soda ash or carbon dioxide, compared on pH adjustment chemicals.
Polyphosphate alone is not an OCCT option: EPA states it is not effective for lead and copper and may increase tap levels.
Targets come from guidance (EPA 816-B-16-003, March 2016, updated 2019), such as EPA's reference window of 1.0 to 3.0 mg/L orthophosphate as PO4 at pH 7.2 to 7.8, which is not a regulatory limit. Chemistries are covered under corrosion control treatment for lead and copper.
Optimal Water Quality Parameters: Minimum pH and Orthophosphate#
Optimal water quality parameters are the State-designated values a system with OCCT must hold: at least pH 7.0 in every distribution sample and at least 0.5 or 1.0 mg/L orthophosphate as PO4 in tap samples (40 CFR 141.82(f)).
The rule states orthophosphates as PO4, never as P, and pH in water treatment without a unit. The table below compares each parameter.
| Parameter | Where measured | Minimum or designation | Section | Basis |
|---|---|---|---|---|
| pH | every distribution sample | at least 7.0, unless the State finds it infeasible or unnecessary | 141.82(f)(2) | pH units |
| pH | entry points | State-designated minimum or range | 141.82(f) | pH units |
| Orthophosphate | tap samples | at least 0.5 mg/L (systems previously without CCT) or 1.0 mg/L (previously with CCT), unless the State finds otherwise | 141.82(f)(4) | as PO4 |
| Silica | entry points and distribution | measured when a silicate inhibitor is used; State-set minimum | 141.82, 141.87 | as SiO2 per method |
| Alkalinity | distribution; entry points when adjusted | measured; dose of the alkalinity-adjusting chemical recorded at entry points | 141.87 | as CaCO3 per method |
| Follow-up WQP sample | each tap site above 0.010 mg/L lead | within 5 days | 141.82(j) | days |
Each tap site above 0.010 mg/L lead needs a follow-up sample within 5 days (40 CFR 141.82(j)). Orthophosphoric acid, sodium phosphates and blends are compared on phosphates in water treatment.
Tap Sampling and Water Quality Parameter Monitoring#
Lead and copper tap samples are 1-liter samples in wide-mouth bottles after at least 6 hours of stagnation, and sites served by a lead service line give both the first and the fifth liter (40 CFR 141.86). Water quality parameter samples (40 CFR 141.87) cover the 5 measurements below.
- pH.
- Alkalinity.
- Orthophosphate as PO4, with an orthophosphate inhibitor.
- Silica, with a silicate inhibitor.
- Inhibitor or alkalinity-chemical dose rate at entry points.
Approved methods (40 CFR 141.23(k)(1) via 141.89(a)) include EPA 365.1 for phosphate in treated water, EPA 150.1 for pH, SM 2320 B for alkalinity of water and SM 4500-SiO2 C for silica.
Lead Service Line Replacement#
LCRI requires lead service lines to be replaced within 10 years, at a cumulative average of at least 10 % per year (40 CFR 141.84(d)(5)).
Which Treatment Chemicals Does the Lead and Copper Rule Affect?#
The Lead and Copper Rule affects 4 groups of treatment chemicals: pH and alkalinity chemicals, such as caustic soda, lime and soda ash; orthophosphate inhibitors, such as phosphoric acid and zinc orthophosphate; silicate inhibitors; and chemicals whose listing limits mirror the rule, such as copper sulfate. The table below lists 17 chemicals in the option order of 40 CFR 141.82(c).
| # | Chemical | Group | How the rule pulls it in | AWWA standard | NSF/ANSI/CAN 60 condition |
|---|---|---|---|---|---|
| 1 | sodium hydroxide (caustic soda) | pH and alkalinity | alkalinity and pH adjustment, first OCCT option | ANSI/AWWA B501-25 | product MUL |
| 2 | hydrated lime | pH and alkalinity | alkalinity and pH adjustment | ANSI/AWWA B202-25 | product MUL |
| 3 | soda ash | pH and alkalinity | alkalinity and pH adjustment | ANSI/AWWA B201-18 | product MUL |
| 4 | sodium bicarbonate | pH and alkalinity | alkalinity adjustment | none | product MUL |
| 5 | carbon dioxide | pH and alkalinity | pH and DIC adjustment with an alkali | ANSI/AWWA B510-18 | product MUL |
| 6 | calcite (calcium carbonate) media | pH and alkalinity | alkalinity and pH adjustment | none | NSF/ANSI/CAN 60 category Calcium Carbonate |
| 7 | phosphoric acid | orthophosphate inhibitor | orthophosphate OCCT; 0.5 or 1.0 mg/L as PO4 minimum | ANSI/AWWA B507-23 | product MUL |
| 8 | monosodium phosphate | orthophosphate inhibitor | orthophosphate OCCT | ANSI/AWWA B504-24 | product MUL |
| 9 | disodium phosphate | orthophosphate inhibitor | orthophosphate OCCT | ANSI/AWWA B505-24 | product MUL |
| 10 | trisodium phosphate | orthophosphate inhibitor | orthophosphate OCCT | no current AWWA standard | product MUL |
| 11 | zinc orthophosphate | orthophosphate inhibitor | orthophosphate OCCT; zinc is not a water quality parameter | ANSI/AWWA B506-25 | [ZN] zinc ≤ 2.0 mg/L |
| 12 | blended phosphates | orthophosphate inhibitor (blend) | OCCT only through its orthophosphate fraction | none (blend) | product MUL |
| 13 | sodium silicate | silicate inhibitor | silicate OCCT; silica monitored | ANSI/AWWA B404-22 | product MUL |
| 14 | zinc salts (zinc sulfate, zinc chloride) | zinc source in inhibitor blends | used with orthophosphate | none | [ZN] zinc ≤ 2.0 mg/L |
| 15 | sodium hexametaphosphate (SHMP) | polyphosphate | not effective alone for lead and copper | ANSI/AWWA B502-23 | product MUL |
| 16 | sodium tripolyphosphate (STPP) | polyphosphate | not effective alone for lead and copper | ANSI/AWWA B503-23 | product MUL |
| 17 | copper sulfate | reservoir algaecide | adds copper; listing cap equals the copper action level | ANSI/AWWA B602-25 | copper ≤ 1.3 mg/L |
AWWA standards list, 2026-10-20; NSF listings, 2026-10-20; MULs are product-specific, as product. Editions are indexed under AWWA B-series standards.
Orthophosphate dosing raises the phosphorus load at the receiving wastewater plant by 10 to 35 %, median 20 % (Rodgers 2014, cited in EPA 816-B-16-003), which counts against NPDES permits and local pretreatment limits.
NSF/ANSI/CAN 60 is required in 49 US states (NSF survey of ASDWA members); its listing conditions cap copper at 1.3 mg/L and zinc at 2.0 mg/L in finished water, and maximum use levels per product are explained on NSF/ANSI/CAN 60.
How Do Water Systems Document Lead and Copper Rule Compliance?#
Water systems document Lead and Copper Rule compliance in 6 steps, from the service line inventory to the State's designation of optimal water quality parameters. The steps are listed below.
- Maintain the lead service line inventory required since 2024-10-16.
- Collect tap samples under 40 CFR 141.86.
- Compare the 90th percentile with the action level in force on the sampling date.
- Run an OCCT study when the rule or the State requires it.
- Measure water quality parameters with 40 CFR 141.23(k)(1) methods.
- Hold the designated parameters and record the inhibitor dose rate.
The State sets system-specific deadlines and report formats; this summary does not replace them.
How to compare program providers is covered under water treatment companies.
LCRI Timeline: Final Dates and Pending Items#
The Lead and Copper Rule Improvements (89 FR 86418, 2024-10-30) took effect on 2024-12-30; community and non-transient non-community water systems must comply by 2027-11-01 (40 CFR 141.80(a)(3)), when the lead action level becomes 0.010 mg/L (0.015 mg/L until then). The table below separates final steps from the pending compliance date.
| Date | Status | Instrument | What it changes |
|---|---|---|---|
| 1991-06-07 | final | LCR | lead 0.015 mg/L and copper 1.3 mg/L action levels; corrosion control treatment |
| 2021-01-15 | final | LCRR, 86 FR 4198 | lead service line inventory; trigger level |
| 2021-06-16 | final | 86 FR 31939 | LCRR delay |
| 2024-10-08 | signed and announced | LCRI | final rule announced |
| 2024-10-16 | compliance date | LCRR retained provisions | inventory and notifications apply |
| 2024-10-30 | published | LCRI, 89 FR 86418 | final rule text |
| 2024-12-30 | effective | LCRI | rule effective (141.80(a)(2)) |
| 2026-10-20 | eCFR check | 40 CFR 141.80 to 141.93 | no amendment after 2024-12-30 |
| 2027-11-01 | pending (compliance date) | LCRI | 0.010 mg/L lead action level; minimum pH and orthophosphate; OCCT and phosphate programs re-evaluated |
EPA's LCRI page was last updated on 2025-12-29.
Official Sources for the Lead and Copper Rule#
The official sources for the Lead and Copper Rule are the eCFR text of 40 CFR 141 subpart I, the LCRI final rule in the Federal Register and 3 EPA pages. They are listed below.
- eCFR, 40 CFR 141.80 to 141.93 (2026-10-01).
- Federal Register, 89 FR 86418 (2024-10-30).
- EPA, "Lead and Copper Rule Improvements" (2025-12-29).
- EPA, "Lead and Copper Rule Implementation Tools".
- EPA, "Optimal Corrosion Control Treatment Evaluation Technical Recommendations" (EPA 816-B-16-003).
This page summarizes official requirements for information only and is not legal advice; for a compliance decision, check the current official text and consult the competent authority or a qualified legal adviser.
How Do Lead and Copper Rules Compare in the EU, Canada and WHO Guidance?#
The EU and Canada set lead as a maximum value for drinking water rather than as an action level, and both use lower long-term lead values than the US action level.
US, EU and international rules are compared under water treatment regulations and standards, with the EU Drinking Water Directive 2020/2184 and WHO Guidelines for Drinking-water Quality on their own pages.
EU and Canadian Lead and Copper Values#
Two jurisdictions outside the US set the lead and copper values listed below.
- EU: lead 10 µg/L until 2036-01-12, then 5 µg/L; copper 2.0 mg/L (Directive (EU) 2020/2184, Annex I Part B).
- Canada: lead maximum acceptable concentration (MAC) 0.005 mg/L, as low as reasonably achievable; copper MAC 2 mg/L, aesthetic objective 1 mg/L (Health Canada, 2019).
Is the Lead Action Level an MCL?#
No: the 0.010 mg/L lead action level is a trigger for corrosion control, sampling and replacement steps under 40 CFR 141.80(c), not a maximum contaminant level, and the inorganic MCL list of 40 CFR 141.62 has no lead entry.
Do Polyphosphates Meet the Lead and Copper Rule Corrosion Control Requirements?#
No: polyphosphates alone are not effective for lead and copper and may increase tap levels (EPA), and the OCCT options of 40 CFR 141.82(c) name orthophosphate- or silicate-based inhibitors.
Their main role is covered under polyphosphates for sequestration and scale control.
Which NSF/ANSI/CAN 60 Listings Cap Copper at 1.3 mg/L?#
NSF/ANSI/CAN 60 listings of copper sulfate algaecides and of copper-containing aluminum sulfate blends (footnote [CP]) cap copper in finished water at 1.3 mg/L, the same value as the copper action level (NSF listings, 2026-10-20).