Review of historical plumbing codes for lead service line inventories in the United States.

Inventorying and replacing lead service lines (LSLs) is a national priority in the United States (US), with records review conducted as a first step. Among other records, historical plumbing codes can provide cutoff dates for LSL allowance in the US. This work identified and reviewed historical national plumbing codes for mention of lead for drinking water pipe and found that lead pipe was permissible for service lines by the Basic Plumbing Code until 1978, the Uniform Plumbing Code until 1988, and the Southern Standard Plumbing Code until 1977/78. Overall, identifying pertinent code titles over time and obtaining them was challenging because those records were not readily available. Once obtained, interpreting the code language also proved challenging. Terminology initially reflected sanitary systems before drinking water systems were incorporated, and code editions through the years reorganized the content and specific mentions of lead in service lines within text. This review focused on model plumbing codes, which are then adopted at the state or local level, typically with modifications that also need to be understood. Two practical examples of service line inventory development were also summarized. These examples highlighted placing different emphasis on plumbing code review.