Lead doesn't come from the water treatment plant. It enters the water supply at the pipes, solder, and fixtures the water passes through after leaving treatment—at the utility's service line, at building plumbing connections, and at individual fixtures. That distinction determines everything about how lead contamination works, what your utility's test results tell you, and what they don't.
The complete tap water guide for businesses covers lead alongside the full range of contaminants in municipal water. This piece goes deeper on lead specifically—where it enters the water stream, what December 2024's regulatory changes require, what the utility's aggregate reporting does and doesn't show, and which buildings carry the most risk.
Why Lead Enters Water at the Tap
Municipalities treat water to meet EPA standards before it enters the distribution system. After that, water travels through distribution mains, service lines, and your building's internal plumbing before reaching any faucet. Lead from pipes, solder, or fittings anywhere along that path dissolves into water—especially water that has been sitting in contact with lead-containing materials for several hours.
The EPA estimates that between 6.1 and 10 million lead service lines remain in use across the United States. A service line is the pipe connecting the municipal distribution main to your building. In cities built out in the late 19th and early 20th centuries, lead was the standard material because it was malleable and easy to work with. Many of those lines were never replaced as buildings changed hands.
Inside buildings, the risk shifts to interior plumbing. Congress banned lead-based solder for drinking water plumbing in the 1986 Safe Drinking Water Act amendments. Buildings constructed or substantially replumbed before 1986 are likely to have lead-containing solder at joints, lead-containing fittings, and in some cases lead pipe sections. All of it can leach lead into water that sits in contact with it.
What the December 2024 Lead and Copper Rule Changes
The EPA finalized the Lead and Copper Rule Improvements on December 30, 2024—the most significant update to lead regulation since the original 1991 rule. Two changes matter most for facilities managers.
The action level dropped from 15 parts per billion to 10 parts per billion. When a utility's 90th percentile test result exceeds the action level, it must implement corrosion control treatment, public notification, and service line replacement. More systems will now trigger that required response.
The rule also requires utilities to complete a full inventory of lead service lines and replace them all within ten years. That replacement obligation falls on the utility, not building owners. Contact your utility to ask whether your address is in their lead service line inventory—if it is, your line is now on a replacement timeline.
The rule does not address lead from building-owned internal plumbing. If your building's pipes and solder are the contamination source rather than the utility-owned service line, that remains your responsibility.
What Utility Lead Reporting Actually Tells You
The Lead and Copper Rule requires utilities to test lead at a sample of high-risk homes—older properties with lead service lines or lead solder plumbing. The reported compliance figure is the 90th percentile of that sample. If the 90th percentile falls below the action level, the system is in compliance.
That figure is a system-wide aggregate. It does not reflect what comes out of your building's specific faucets on any given day. A utility with a 90th percentile of 8 ppb—compliant under both old and new rules—may still have individual buildings where tap readings are significantly higher, depending on the age of the plumbing and how long water has been sitting in pipes.
Your annual Consumer Confidence Report includes the 90th percentile result, not building-specific results. The Consumer Confidence Report guide walks through how to read it and what it does not cover. The only way to know your building's actual lead level is to test at the tap—a certified lab can run a tap water lead test for approximately $20 to $50.
Which Buildings Carry the Most Risk
Buildings constructed before 1986. Any commercial property built before that year should be treated as having a potential lead source in its plumbing until testing establishes otherwise. This includes office buildings, healthcare facilities, warehouses, and any other commercial property with original plumbing infrastructure. Lead-based solder at pipe joints—and possibly lead pipe sections—are the risk.
Buildings on lead service lines in older cities. Even a building with fully modern interior plumbing can have elevated lead levels if the utility-owned service line is lead. Lead service lines are most concentrated in cities with older infrastructure: Chicago, Detroit, Cleveland, Milwaukee, Philadelphia, Pittsburgh. Milwaukee has one of the highest concentrations of lead service lines per capita of any major U.S. city. Philadelphia's water authority has identified tens of thousands still in use.
The EPA's position is unambiguous: there is no level of lead in drinking water that has been determined to be safe. At low levels of chronic exposure, lead causes neurological damage in children. In adults, sustained exposure contributes to hypertension, kidney disease, and cardiovascular effects.
How Reverse Osmosis Removes Lead
A reverse osmosis membrane blocks dissolved ionic compounds at the molecular level. Lead in water is present as dissolved lead ions—rejected by the RO membrane before water reaches the dispenser. Studies on RO performance for lead removal document removal rates of 95 percent or higher under normal operating conditions.
Pre-treatment carbon stages upstream of the RO membrane remove chlorine and chloramines that would otherwise degrade the membrane over time. The full sequence—carbon pre-treatment, RO membrane, polishing carbon—addresses lead along with PFAS, arsenic, nitrates, and other dissolved contaminants in a single purification process.
For buildings where lead plumbing is a concern, a bottleless water purification system with RO at the point of use removes lead before employees drink it, regardless of what the building's pipes or utility service line contribute to the incoming supply.
Frequently Asked Questions
Does the water treatment plant remove lead?
Utilities treat water for many contaminants, but treatment doesn't eliminate lead that enters water after it leaves the plant—from utility-owned service lines and building plumbing. Corrosion control treatment (adding phosphates to coat pipe interiors) can reduce leaching but doesn't eliminate it. Point-of-use purification is the only way to address lead that enters after the distribution system.
What did the December 2024 Lead and Copper Rule Improvements change?
The action level dropped from 15 parts per billion to 10 parts per billion, and utilities must now complete a full lead service line inventory and replace all lead service lines within ten years. The rule applies to utilities, not building owners. Internal plumbing within a building remains the building owner's responsibility.
Is my building at risk if it was built before 1986?
Potentially, yes. Lead-based solder for drinking water plumbing was legal until 1986. Buildings constructed or substantially replumbed before that year may have lead-containing solder at pipe joints, lead fittings, or lead pipe sections. Testing at the tap is the only way to know what your building's plumbing specifically contributes.
My utility's lead test results are below the action level. Does that mean my building is safe?
Not necessarily. The utility's 90th percentile result reflects a sample of high-risk homes in the system, not your building's specific faucets. A system-wide compliant result can coexist with individual buildings where tap readings are elevated. Independent tap testing is the only way to establish your building's actual exposure.
How does reverse osmosis remove lead?
Lead is present in water as dissolved ionic compounds. The RO membrane rejects dissolved ions—including lead—based on size and charge at the molecular level. Studies consistently document RO lead removal rates of 95 percent or higher. The same process that removes PFAS and arsenic removes lead, with no additional equipment required.