My washer overflowed — what do I do?
Immediately turn off the water supply valves behind the washer (or the whole-house valve), unplug the unit, and dry standing water with towels and a wet-vac before it reaches drywall or subflooring. Then call for service — an overflow means the water-inlet valve or a clogged drain is failing and will happen again.
Step 1: cut the supply. Behind every washer are two valves (hot and cold). Close them. If they're stuck from never being turned, shut off the main house water supply instead — you can fix the valves later.
Step 2: cut power. Don't stand in water and touch the machine. If the outlet is wet or water is anywhere near the power cord, kill the breaker for the laundry circuit first.
Step 3: water mitigation. Towels, then a wet-vac. Pull the washer away from the wall if you can do so safely. Water wicks into drywall and subfloor faster than you'd think — in under 24 hours you can have mold growing. If the water got under flooring, call a water-mitigation specialist the same day.
Step 4: diagnose. Overflow is almost always one of: a stuck water-inlet valve that keeps filling after the sensor says stop, a failed pressure switch, or a drain hose blockage. Any of these is a service call — do not use the washer until the root cause is fixed.
Insurance note: if the overflow caused property damage, photograph everything before cleanup and call your homeowner's or renter's insurance same day.