Lead service lines are one of the most important potential sources of lead in drinking water, especially in older residential areas. A service line is the pipe that connects a building to the city water main in the street. In many older cities, this connection was sometimes made with lead because lead was once considered a practical plumbing material. It was flexible, durable, and easy to shape around foundations, sidewalks, narrow streets, and underground utility routes. Today, lead is no longer considered safe for drinking water infrastructure, but some older service lines may still remain underground in historic neighborhoods.
In northeastern cities such as New York, Jersey City, Hoboken, Newark, Philadelphia, Boston, and surrounding older communities, many buildings were constructed before modern drinking water plumbing standards. Brownstones, row homes, apartment buildings, co-ops, multi-family houses, and older commercial properties may have service lines installed during earlier periods of development. Even when the visible plumbing inside a building has been updated, the buried connection from the water main to the property may still be older, partially replaced, or unknown.
Lead can enter drinking water when water passes through a lead service line and corrosion occurs. The water may pick up dissolved lead or small lead particles before it reaches the building’s interior plumbing. This can happen even when municipal water has already been treated and meets required standards before entering the distribution system. The final water quality at the tap depends not only on the public water supply, but also on the service line and plumbing materials between the street and the faucet.
Because service lines are underground, property owners and residents may not know what material connects their building to the city water system. Utility records, service line inventories, public maps, plumbing inspections, and water testing can help identify potential concerns. If a lead service line is present, full replacement is generally considered the strongest long-term solution because it removes a major possible source of lead from the drinking water pathway.
Lead solder is another common source of lead in older plumbing systems. Solder is the metal material used to join pipe sections together, especially in copper plumbing. Before modern plumbing regulations restricted lead in drinking water systems, solder containing lead was widely used in homes and buildings. This means a property may have copper pipes that look modern or safe at first glance, while the joints connecting those pipes may still contain lead solder. Because solder is often hidden behind walls, ceilings, floors, or inside mechanical spaces, it can be difficult to identify without a plumbing review.
Older residential infrastructure in northeastern cities often includes plumbing installed, repaired, and modified over many decades. A Brooklyn brownstone, a Manhattan co-op, a Jersey City row home, or a Hoboken apartment building may contain a mix of original plumbing, partial upgrades, and newer fixtures. During renovations, property owners may replace kitchens, bathrooms, faucets, or visible pipes, but older soldered joints may remain in less accessible areas. This creates a layered plumbing system where both old and new materials exist together.
Lead solder can release lead into drinking water when corrosion occurs at pipe joints. Water that sits inside the plumbing system for several hours, such as overnight or during a period of non-use, may have more contact with soldered connections. If the solder contains lead, small amounts may dissolve into the water before it reaches the faucet. The amount can vary depending on water chemistry, pipe condition, stagnation time, temperature, and how frequently the fixture is used.
Understanding lead solder is important because lead concerns are not limited to underground service lines. A building may not have a lead service line but may still have lead-containing solder within interior plumbing. For older homes, apartments, brownstones, and multi-family properties, water testing can help determine whether lead is present at the tap, while plumbing inspections can help identify whether soldered joints or other interior components may be contributing to the issue.
Brass fixtures and plumbing components may also contribute lead to drinking water, especially when they were manufactured before stricter modern standards. Brass has long been used in plumbing because it is strong, durable, and resistant to corrosion. It can be found in faucets, valves, fittings, connectors, meters, shutoff components, and other parts that come into contact with drinking water. Historically, lead was often added to brass to make it easier to machine and manufacture. As a result, older brass components may contain lead even if the main pipes are not made of lead.
This issue is especially relevant in older residential buildings common across northeastern cities. A Manhattan apartment may have a newer kitchen faucet but older shutoff valves beneath the sink. A Brooklyn brownstone may have modern bathrooms while older brass fittings remain near the meter or basement plumbing. A Jersey City or Hoboken row home may have updated visible fixtures but older valves, connectors, or service components still in place. Because plumbing upgrades often happen in stages, lead-containing brass parts may remain for many years without being obvious.
Lead from brass components can enter water through corrosion or prolonged contact. Water sitting inside a faucet, valve, or fitting overnight may interact with the metal before being used in the morning. In some cases, a specific fixture may contribute more lead than the rest of the plumbing system. This is why water test results can vary from one faucet to another within the same building. A kitchen tap may show a different result than a bathroom sink, basement faucet, or utility room outlet.
Replacing outdated fixtures and components may help reduce lead from specific taps, but it may not solve every source if the building also contains lead solder, old service lines, or other legacy materials. For a complete water quality evaluation, residents and property owners should consider the full plumbing pathway. Laboratory testing, fixture review, service line verification, and professional plumbing inspection can all help identify whether brass components may be part of the lead source.