11.2 The Lead and Copper Rule and Service Line Replacement

Action Levels, Not MCLs

Lead and copper are unusual: they are regulated by action levels measured at the customer's tap rather than by maximum contaminant levels measured at the plant. The reason is that neither metal typically originates in the source. Lead comes from lead service lines, lead solder, and brass fixtures; copper comes from copper premise plumbing. How much dissolves is a function of finished water chemistry - which is why the rule's central requirement is optimal corrosion control treatment, and why the rule is fundamentally about the operator's pH, alkalinity, and inhibitor control.

The 90th Percentile Calculation

1. Sort all valid tap results from lowest to highest.
2. Multiply the number of samples by 0.9.
3. The result identifies the sample position whose value is the 90th percentile. For sample counts that are multiples of 10 the position is exact; otherwise round to the nearest whole sample position (for very small sets of five samples, average the fourth and fifth highest).

Worked example. A system collects 20 samples. 20 x 0.9 = 18, so the 18th value in ascending order is the 90th percentile. If that value is 0.019 mg/L, the system has exceeded the lead action level.

[!IMPORTANT] Exceeding an action level is not an MCL violation. It is a trigger. The system must then take a defined series of actions - and it can be in violation for failing to take those actions, not for the number itself. That distinction is tested constantly.

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Sample Site Selection and Collection Protocol

Sites are selected by tier, highest risk first:

If not enough Tier 1 sites exist, the system moves down the tiers, documenting why.

First-Draw Protocol

• Cold water tap used for drinking, in a kitchen or bathroom
• At least six hours of stagnation (and typically not more than 12) before collection
• One liter collected at the normal flow rate
• Do not remove, clean, or replace the aerator before sampling - removing the aerator discards the particulate lead the sample is meant to capture
• Do not pre-flush the line the night before
• Samples are usually collected by the customer following written instructions, which makes clear instructions and follow-up an operator responsibility

Monitoring is typically at standard six-month periods during June through September for a new or exceeding system, reducing to annual and then triennial for systems with a sustained record below the action levels, plus required water quality parameter (WQP) monitoring for pH, alkalinity, calcium, conductivity, temperature, and orthophosphate or silica in the distribution system and at entry points.

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What Happens on an Action Level Exceedance

Once OCCT is designated by the State, the system must operate within its designated water quality parameter ranges continuously. Falling outside those ranges - for example letting the orthophosphate residual or the pH drift below the designated minimum - is a treatment technique violation independent of any tap result.

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Service Line Inventory and Replacement

Under the Lead and Copper Rule Revisions (LCRR), every community and non-transient non-community water system had to develop an initial service line inventory identifying the material of every service line - both the utility-owned and the customer-owned portion - classified as lead, galvanized requiring replacement, non-lead, or lead status unknown. The inventory must be publicly accessible, and systems with lead, galvanized-requiring-replacement, or unknown lines must notify those customers.

Galvanized requiring replacement means galvanized pipe that is or was ever downstream of a lead service line; galvanized pipe adsorbs and later releases lead, so it is treated as a lead line for replacement purposes.

The Lead and Copper Rule Improvements (LCRI)

EPA finalized the LCRI on October 30, 2024, effective December 30, 2024, with a compliance date of November 1, 2027. The three changes operators must know:

1. The lead action level drops from 0.015 mg/L to 0.010 mg/L.
2. Mandatory replacement of lead and galvanized-requiring-replacement service lines within 10 years, on a replacement plan that prioritizes replacement using community-specific factors, including populations disproportionately affected by lead.
3. Strengthened tap sampling, inventory validation, and public communication requirements.

The three years between the effective date and the November 2027 compliance date are a deliberate transition period for systems to build inventories, plan replacements, and re-optimize corrosion control against the lower action level.

[!WARNING] Partial replacement is disfavored for a physical reason. Replacing only the utility-side portion leaves lead in contact with new copper, creating a galvanic couple in which the lead corrodes faster, and the physical disturbance releases accumulated particulate lead. Any service line disturbance requires flushing instructions and a certified point-of-use filter for the customer, plus follow-up sampling.