AB-03Check for cables and pipes, and know your isolation pointsCables and pipes can run almost anywhere, not just in the marked safe zones, so treat your detector as a first check, not a guarantee — it can miss cables that are deep, in metal conduit, behind metal-backed plasterboard, or confused by a metal stud frame. Find your stopcock now, usually under the kitchen sink, and check it turns freely so you can shut off water fast if you hit a pipe. If you have any doubt about what's behind the wall, isolate the relevant circuit at the consumer unit before drilling, and turn off the water at the stopcock before cutting into anything that could carry it.