HP-02Isolate before you do anything elseIf there is any chance you hit a cable, go to the consumer unit (the grey box with switches that controls power to the house, usually under the stairs or near the meter) and switch off the relevant circuit, or the main switch if unsure. If there is any chance you hit a water pipe, turn off the stopcock (the valve where mains water enters the house, often under the kitchen sink or near the stairs) by turning it clockwise. Do this even if a cable or pipe detector said the area was clear. Detectors can miss cables that are deep, in metal conduit, behind metal-backed plasterboard, or simply routed somewhere unexpected, especially in older houses. Expect something to be there and prove otherwise, rather than trusting a clear reading alone.