Metal pipes have been used in residential plumbing for centuries. While modern materials like copper and plastics are generally safe, older metallic components pose a public health concern. The risk centers on the ability of certain metals to corrode and leach into the drinking water supply, compromising water quality. Understanding the source of these metals is the first step in protecting your family’s health from hidden contaminants in the home’s plumbing.
Identifying the Primary Metal Threats in Plumbing
The most significant threat comes from lead service lines and older fixtures, a material banned from new plumbing construction decades ago. Lead pipes are soft, dark gray, and can be easily scratched to reveal a shiny, silver metal beneath the surface. They were commonly used for the water service line connecting a home to the municipal water main, and many remain in use today.
Galvanized steel pipes, which are steel coated in zinc, represent a complex issue. Installed often as a replacement for lead, they are dull gray and magnetic. As the zinc coating corrodes, it exposes the underlying steel, which rusts. More critically, the zinc layer often contained lead impurities that can be released into the water. Corrosion also leads to scale buildup, which can trap lead particles from upstream sources like lead service lines or solder.
Beyond the main service lines and pipes, other fixtures can also contribute to contamination. Older brass faucets, valves, and fittings frequently contain small amounts of lead, which was added to make the metal easier to machine. While modern “lead-free” brass is now mandated, older components can still release lead into the water that sits within them. Modern copper pipes are generally considered safe, although they can release copper into the water under certain corrosive conditions.
How Metals Enter the Water Supply
Metals move from the pipe walls into the water primarily through corrosion, a chemical reaction influenced by water chemistry. Water that is soft, low in alkalinity, or slightly acidic (lower pH) is more corrosive to metallic pipes. This environment dissolves the metal from the pipe’s interior surface, carrying it away in the water flow.
Warmer water can accelerate the rate at which metals dissolve. Stagnation is also important in determining metal concentration. When water sits motionless in the pipes for an extended period (e.g., overnight), metals have more time to leach into the standing water. This leads to the highest concentrations appearing in the first draw from the tap.
To counteract corrosion, municipal water systems employ control methods. One strategy involves adjusting the water’s pH and alkalinity to promote the formation of a protective layer, or scale, on the pipe’s interior surface. Another method is the addition of orthophosphates, food-grade chemicals that react with metals to create a stable, insoluble coating. This barrier significantly reduces the leaching of lead and copper.
Health Consequences of Metal Exposure
Exposure to metals, particularly lead, presents a serious health risk because there is no known safe level in the human body. Lead is a potent neurotoxin especially harmful to young children whose brains and central nervous systems are still developing. Even low-level exposure is linked to long-term effects like behavioral problems, reduced attention spans, and loss of intelligence quotient (IQ).
In adults, chronic lead exposure is associated with a range of cardiovascular and renal issues. It contributes to increased blood pressure, which raises the risk of heart attacks and other cardiovascular diseases. Lead can also cause kidney damage and reproductive issues in both men and women. Pregnant women are at specific risk because lead crosses the placenta, potentially leading to reduced fetal growth and preterm birth.
Copper is an essential trace mineral, but excess amounts cause health issues. Short-term exposure to high levels of copper results in gastrointestinal distress, including nausea, vomiting, stomach cramps, and diarrhea. Chronic exposure can lead to kidney and liver damage, particularly in sensitive populations such as infants or individuals with Wilson’s disease, which impairs the body’s ability to excrete copper. Rust from galvanized pipes (mostly iron) primarily affects the water’s aesthetics, causing a metallic taste and reddish-brown discoloration. However, this discoloration can signal a compromised pipe releasing more harmful contaminants like lead.
Testing and Mitigation Strategies
The first step in addressing potential contamination is identifying the materials in your service line and home plumbing. Homeowners can perform a visual check where the water line enters the building near the main shutoff valve. Lead pipes are dull gray and non-magnetic, but scratching them reveals shiny, silver metal. Galvanized pipes are also gray, but a magnet adheres strongly to their surface.
Professional water testing is the most reliable way to confirm the presence and concentration of metals. Testing involves collecting two types of samples: a “first-draw” sample and a “flushed” sample. The first-draw sample is taken after water has been stagnant for at least six hours, capturing the highest concentration of leached metals. The flushed sample, collected after running the water for several minutes, indicates metal levels coming from the main service line or further back in the system.
Short-term mitigation involves simple steps to reduce immediate exposure. Running the cold water tap for one to two minutes before using it for drinking or cooking flushes out the stagnant water that has accumulated metals. For a more permanent solution, installing a point-of-use water filter certified to remove lead, such as those meeting NSF standards, offers a targeted barrier at the tap. The most comprehensive and long-term solution is the full replacement of any lead service lines and internal plumbing with modern, lead-free materials like copper or PEX plastic.