The four service line inventory categories defined by EPA — lead, galvanized requiring replacement (GRR), lead status unknown and non-lead — in plain language.
Sources: EPA and CDC, linked inline. Last checked 2026-10-09. This guide is general information, not medical, legal or plumbing advice.
The four categories
Under EPA's lead rules every service line in a utility's inventory is placed in one of four categories (EPA LCRI inventory fact sheet):
- Lead — the service line, or part of it, is made of lead.
- Galvanized requiring replacement (GRR) — EPA: “A galvanized service line that currently is or ever was downstream of a lead service line; or is currently downstream of a lead status unknown service line. … If the water system is unable to demonstrate that the galvanized service line was never downstream of a lead service line, it is a GRR service line.”
- Lead status unknown — EPA: “a service line where the pipe material is not known to be a lead service line, galvanized requiring replacement service line, or a non-lead service line” (EPA inventory tips, 2026).
- Non-lead — EPA: “A service line that is determined through an evidence-based record, method, or technique to not be a lead or GRR service line.”
Why galvanized pipe can need replacement
EPA explains that it requires replacement of GRR lines “because they can adsorb upstream lead particulates and contribute to lead in drinking water even after the original lead source has been removed” (EPA LCRI FAQ).
What “unknown” means for you
Unknown is not a finding that a pipe is lead or safe; it means the utility does not yet have records or an inspection. Under the 2024 Lead and Copper Rule Improvements, “Water systems must identify the material of all unknown service lines in their inventory by their mandatory service line replacement deadline” (EPA). Utilities must also notify people served by lead, GRR and unknown lines each year (EPA).
On this site we show the utility's own category. Some utilities publish separate entries for the utility-owned and customer-owned parts of the line; both are shown where available.
Check your address: look up your service line in your utility's published inventory.
Frequently asked questions
What does GRR mean on a lead service line inventory?
Galvanized requiring replacement: a galvanized service line that is or ever was downstream of a lead service line, or is currently downstream of a line of unknown material. EPA requires these lines to be replaced.
Is a lead status unknown line a lead pipe?
Not necessarily. EPA defines it as a line whose material is not known to be lead, galvanized requiring replacement or non-lead. Utilities must identify all unknown lines by their replacement deadline.