Why sinks fail and when replacement beats repair
Sinks fail at the seals, the drain assembly or the mounting clips, and a crack in the basin itself cannot be repaired reliably. A leaking seal or worn drain often takes a repair, while a cracked or rusted-through basin needs replacement.
Replacement also makes sense when you are changing the countertop or cabinet, because the old sink has to come out anyway.
Signs a sink needs attention
Water pooling under the cabinet, a drain that stays slow after clearing, or a basin that rocks in its cutout all point to a failing connection or mounting. Rust stains around the drain usually mean the metal has thinned.
Catching these early keeps water out of the cabinet base, where it causes rot and mold.
What you can safely check yourself
You can tighten a loose supply connection by hand and clear a hair clog from the pop-up assembly. Shut the water off under the sink before you touch any fitting.
Leave gas connections, sealed drain work and anything behind the wall to a licensed plumber. A master plumber on staff confirms the work meets code.