The unknown pipes
Lead service lines in NYC: 0%. Service lines whose material the city does not know: 0%. They are nearly identical. For every confirmed lead pipe under a NYC building, there is another whose status is a question mark.
In October 2024, the EPA's Lead and Copper Rule Improvements (LCRI) gave every U.S. water utility until December 2037 to find and replace every lead service line in their system. The rule also required something else, less reported: every utility had to publish a parcel-level inventory of which service lines they currently know to be lead, galvanized requiring replacement, non-lead, or unknown.
Here is what the NYC Department of Environmental Protection's inventory looks like today:
0 known-Lead service lines. 0 classified "Unknown - Lead Status Unknown" — meaning the city does not have a record of what kind of pipe is under that building. The two numbers are within 0 of each other. Statistically, the share of NYC's service lines that are known-bad and the share that are unknown are the same number: roughly one in seven service lines in each bucket.
Add the 0 galvanized lines requiring replacement and you get 0 service lines the city has a clear mandate to replace before 2037. But if even half of the 0 unknowns turn out to be lead — which the EPA's modeling assumes is the conservative baseline — the actual replacement queue is closer to twice that. The unknowns aren't a parallel category; they're a future expansion of the lead category, hidden behind the absence of records.
Where the unknowns live
The borough breakdown of Unknowns:
Older neighborhoods with older housing stock tend to have higher Unknown rates, both because record-keeping was worse historically and because installation dates predate consistent documentation requirements. This means the data void compounds the underlying inequity: the neighborhoods most likely to actually have lead pipes are also the ones most likely to be misclassified as Unknown.
Why the math matters
Statewide across New York, ~934,000 service lines carry the Unknown label. The political response has been pointed: the proposed "Find Lead Pipes Faster Act" would empower municipalities to aggressively inspect and reclassify, and the broader "Lead Pipe Replacement Act" would unlock dedicated state budget for remediation. Both bills exist because the open publication of this inventory made the blind spots quantifiable. You can't lobby against a crisis you can't measure.
The lead in your water is a function of what's between the street main and your tap. The things you can see — internal plumbing, fittings, solder — get most of the public attention. The thing you can't see — the service line itself, classified Unknown on a map — is the harder problem.