The Chemistry of Lead Leaching: Why Pipes Corrode and How Water Chemistry Influences Exposure Risk

Lead leaching occurs when lead-containing materials interact with water under conditions that promote corrosion. This process is governed by water chemistry, pipe materials, and contact time.

Corrosion and Lead Release

Corrosion is an electrochemical process where metals dissolve into water. In plumbing systems, corrosion can release lead ions into drinking water when protective scales break down.

Factors that influence corrosion include:

Water pH
Alkalinity
Dissolved oxygen
Disinfectants
Temperature

The Role of pH and Alkalinity

Low pH water is more acidic and increases metal solubility. Low alkalinity reduces buffering capacity, allowing pH fluctuations that accelerate corrosion.

Municipal water systems often adjust pH and alkalinity to minimize lead release, but changes in treatment or plumbing conditions can disrupt these controls.

Disinfectants & Lead Chemistry

Disinfectants such as chlorine and chloramine can influence corrosion dynamics. Changes in disinfectant type have been linked to changes in lead release in some systems.

Particulate vs Dissolved Lead

Lead can enter water as dissolved ions or as particulate matter released from pipe scale. Particulate lead may cause spikes in lead levels and is more difficult to predict.

Why Lead Levels Vary Over Time

Lead levels fluctuate due to:

Water usage patterns
Seasonal temperature changes
Plumbing disturbances
Chemical changes in water supply

Lead leaching is a complex chemical process influenced by water chemistry and plumbing materials. Understanding these factors helps homeowners appreciate why lead levels change and why testing and monitoring are essential tools for managing exposure risk.

By Ryan N., PhD