Shut off the water if you safely can
Locate the closest appropriate shutoff valve or the building's main water shutoff. If you are unsure how to do this safely, avoid damaging plumbing components and get appropriate help.
Look beyond the visible puddle
Water from a broken line can travel under flooring, through wall cavities and into lower levels. The visible wet area may not show the full extent of migration.
Move from repair to restoration
A plumber may repair the failed pipe. Restoration addresses the water that escaped: extraction, material evaluation, drying and related cleanup.