Start at the shutoff
The angle stops under old sinks and toilets have not been turned in twenty years. Turn one now and the packing gives up, so there is a slow weep that was not there this morning. We check the stop before we touch the fixture. Seized stop, water off at the street, small job. Galvanized supply flaking at the threads above it, and at that point you want a licensed plumber, because a faucet swap has turned into repiping and we do not repipe. Condo owners carry a third problem, since the building may own the shutoff and somebody has to warn the neighbors before the riser goes down.
