Most kitchen appliance problems are connection problems rather than appliance failures.
A dishwasher needs its drain hose installed with a high loop or air break so waste water cannot siphon back into the machine. Where this is missing, the symptom is usually water sitting in the bottom of the dishwasher or an odour that returns after every cycle.
Waste disposal units add fine particles to a line that is already carrying fat, which is a combination worth knowing about if a kitchen drain has a history of blocking.
Under sink connections are also where slow leaks hide. A leak behind a kickboard can run for a long time before it becomes visible, and by then it is usually the cabinetry that shows it first.
For a burst pipe or a serious leak, turn the water off at the mains tap before you call. If water is anywhere near power points, the switchboard or light fittings, stay clear and treat it as an electrical hazard. Do not enter standing water in a room with live power.