Lead and Copper Rule & Sampling

Overview of the Lead and Copper Rule

In 1991, the U.S. Environmental Protection Agency (EPA) published a regulation called the Lead and Copper Rule (LCR) that requires water suppliers to control lead and copper in drinking water using corrosion control measures. Corrosion control is an effective way to reduce the release of these metals from plumbing materials into drinking water.

The Lead and Copper Rule focuses on lead because of lead’s potent toxicity, especially to children. Copper is an essential nutrient and is beneficial at appropriate doses. However, exposure to too much copper can adversely impact health.

The Revised 2018 Michigan Lead and Copper Rule, and Sampling Requirements

The revised Michigan Lead and Copper Rule created more requirements to reduce the risk of exposure to lead and copper in drinking water.

The Lead and Copper Rule has specific requirements for how lead and copper water samples are collected. In homes with lead service lines, the first liter and the fifth liter out of the tap are collected. The first liter represents water from household fixtures, and the fifth liter is likely to represent water from the lead service line.

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2020 Lead and Copper Sampling Results

We completed our annual lead and copper sampling.

  • We sampled 51 homes.
  • Our 90th percentile for lead is 9 parts per billion (ppb) and 0.0 parts per million (ppm) for copper.
  • No samples exceeded the lead action level of 15 ppb or the copper action level of 1.3 ppm set by the Environmental Protection Agency (EPA) and the State of Michigan.
  • The 90th percentile is the minimum level of lead found in the highest 10 percent of samples collected.
  • The action level is the concentration of lead, that if exceeded, triggers treatment and other requirements.

Corrosion control, and why do we use it for drinking water?

Corrosion in pipes can cause the release of metals, including lead and copper, into water. Corrosion control treatment is the process of adding a chemical at the water treatment plant to reduce the potential of corrosion in pipes that carry water. Effective corrosion control treatment limits corrosion in pipes and can reduce the release of lead into drinking water.

What is the 90th percentile and what does it mean?

The 90th percentile of sampling results is used to determine if corrosion control is performing as expected. The 90th percentile is the concentration for which 90% of collected samples are less than the 90th percentile and 10% are greater than the 90th percentile.

For example, if the 90th percentile lead concentration for a community is 6 ppb, that means that 90% of samples from that community have lead concentrations lower than 6 ppb. The other 10% of samples have lead levels over 6 ppb and may be greater than 15 ppb. The 90th percentile of the sample results must be below the lead action level of 15 ppb, and 12 ppb starting in 2025.