What is connected to what is a live question
Ann Arbor's stormwater program has focused on how footing drains and other sources connect to the sanitary sewer, because those connections drive basement backups in heavy rain. For plumbing work that makes the existing connections worth establishing rather than assuming. Frost depth is the other local constant, governing how exterior and unheated-space runs have to be protected.
Official sources
Establish existing connections before altering them
Citywide guidance cannot tell you how your footing drain is connected, what your service piping is made of, or where a line runs through unheated space. Establish all three before work rather than during it.
Research date
Sources reviewed June 20, 2026. External requirements and maps can change.