Lead and copper rule
The "lead and copper rule", or LCR, was introduced by the United States Environmental Protection Agency in 1991 to limit the concentration of lead and copper allowed in public drinking water at the consumer's tap, as well limiting the permissible amount of pipe corrosion occurring due to the water itself. It was created following studies that concluded that copper and lead have an adverse effect on individuals. The LCR sought to therefore limit the levels of these metals in water through improving water treatment centers, determining copper and lead levels for customers who use lead plumbing parts, and eliminating the water source as a source of lead and copper. If the lead and copper levels exceed the "action levels", water suppliers are required to educate their consumers on how to reduce exposure to lead. A 2004-2005 study of the LCR by the EPA noted that the system had been effective in 96% of systems serving at least 3,300 people.

# Background
A 1993 article in the Journal of Environmental Health pointed out that four million lead service line pipes were being used at the time. Lead was an ideal material for piping as it had a low corrosion level due to the layer of lead carbonate that would form on the surface of the pipe. However, water with low pH and low calcium levels prevented formation of calcium carbonate; furthermore, the acidity of the water would dissolve the lead from the piping into the water.
The Safe Drinking Water Act was amended in 1986 to ban lead solders with a lead content of more than 0.2% and lead piping with more than 8% lead.

# Adoption
Following the adoption of the LCR rule in May 1991, suppliers serving more than 50,000 people were required to survey their own corrosion control systems and to replace their pipelines with state-approved corrosion control by January 1, 1997. Suppliers who served a smaller number of people only had to replace their pipelines if action levels were exceeded at the tap.
The established action level for lead is 0.015 mg/L, and the level for copper is 1.3 mg/L. To stay within the LCR requirements, water suppliers must strictly monitor their water, improving it whenever possible. Not only is it required that there cannot be lead or copper in the water source, but steps must be taken to reduce lead and copper levels in plumbing whenever possible. To achieve this, water can be treated to be as non-corrosive as possible. If water suppliers can not fulfil the standards set by the LCR, they must adopt stricter filtration and monitoring methods. Ultimately, a water supplier may need to replace its lead piping if it cannot keep levels down.
January 2000 saw the introduction of the Lead and Copper Rule Minor Revisions, or LCRMR, which required water suppliers to install the best available corrosion control mechanisms and to continually observe water levels, even if corrosion control was implemented. These revisions were effective as of April 11, 2000.

# Criticism
The EPA was investigated by the Government Accountability Office in 2003 following the discovery of higher-than-acceptable copper and lead levels in tap water in the District of Columbia. The GAO reported that the EPA had not been collecting copper and lead levels from the states despite claims that the levels of copper and lead have decreased; data for 72% of water systems was missing. The EPA may have been lacking data due to the fact that more resources were being dedicated to lead regulation than lead reporting.