For a condo HOA, the homeowner contracted out to examine a leak in a parking garage near the laundry room. A second technician upstairs checked and tested the drain pipes in the garage by running several fixtures in the unit suspected of leaking. The leak was coming from a drain pipe hidden behind the master bath wall and hallway. We deployed a moisture monitor on-site and discovered a secondary leak in the kitchen wall area beneath the adjoining unit’s refrigerator. We then cut a part of cast iron and replaced it with ABS pipe where the leak was found. We tested for any additional leaks by running water from the two units where repairs were completed.