Called out originally to diagnose a leak in the garage ceiling. Found that on the garage ceiling, relative to the master bathroom shower upstairs, there was a residue of a leak at some point that currently was not leaking. After running the shower and vanities in said location found that neither were leaking when running. Homeowner states that when they filled the tub and drained it from a different bathroom that that is when the leak would occur. Fill the tub to test, held water in tub for approximately 30 minutes and no leak occurred. When speaking to the homeowner in the garage, approximately 20 minutes after shutting off all sources of water, the leak started to happen in the garage ceiling. Since the leak started when no fixtures were running, began by only running single fixtures and waiting to see if the leak would reappear. Ran the shower in the master bathroom for approximately 30 minutes and no leak occurred, but after approximately 15 to 20 minutes after shutting off the sho