You show up to a service call. Customer says "water under the kitchen sink." You walk in, pull the cabinet doors open, and there's standing water on the cabinet floor. Not dripping — sitting.
What do you do first?
A lot of guys go straight for the wrench. Don't. Your first move every time is to figure out if the water is STILL coming or if this is leftover.
Reach in with a paper towel and wipe an area dry. Wait 30 seconds. Does water reappear? If yes — you've still got active pressure somewhere. If no — the leak already sealed itself and you're dealing with residual.
That one step tells you exactly what you're walking into. Active leak means shut-off valve trip first. Residual means you can take your time diagnosing.
When you walk into a water-damage call, what's the first thing you check?