1. A flexible supply hose.
The braided hoses feeding your washing machine, and the smaller ones under sinks and behind toilets.
Why they fail: they're a wear item with a finite life, they're under constant pressure, and they give no warning.
Why they're the worst: a washing machine hose delivers water at full supply pressure into a laundry room, often behind a machine nobody moves, sometimes for hours before anyone notices.
The ten minutes: look at yours. Note their age if you can, and replace anything visibly aged, kinked, corroded at the fittings, or simply unknown. Fit a lever-handle shut-off you can actually turn behind the washing machine. And turn the taps off behind the machine when you're away for more than a few days.
2. The water heater.
Why it fails: the tank corrodes from the inside over years, and when it goes, it goes at the seam or the base — dumping the full contents and then continuing to fill and leak. Relief valves also discharge, and drain valves weep.
The ten minutes: find the cold inlet shut-off at the top of the tank and check it turns. Photograph the rating plate so you know its age. Look at the floor around it and underneath for staining. If the tank is well past a decade old and sitting above a finished space, that's a replacement to schedule rather than to discover.
3. A toilet supply line or overflow.
Why it fails: the supply line or its connection at the tank, a fill valve that won't shut off, or a blockage that turns a flush into an overflow.
The ten minutes: check the shut-off valve behind every toilet actually closes — a surprising number are seized, and a seized stop turns a small overflow into a whole-property shutdown. Replace any that won't turn. And know that lifting the tank lid and pushing the flapper down by hand stops an overflow instantly.
4. A frozen pipe in an unheated space.
Why it fails: water expands as it freezes and splits the pipe — and the flood arrives on thawing, not on freezing.
Where: crawlspaces, attics, garages, exterior walls, and unheated outbuildings.
The ten minutes: insulate what's exposed, seal the air leaks near it (cold air reaching a pipe matters more than the outdoor temperature), disconnect hoses before winter, and isolate exterior taps. If you're leaving the property in winter, don't switch the heat off entirely.
5. A sump pump that doesn't run.
Why it fails: it sits idle for months, then is asked to work continuously during the exact weather that also causes power cuts. Seized impellers, stuck floats, and blocked discharge lines all show up at the worst moment.
The ten minutes: pour a bucket of water into the pit and confirm it starts, runs, and stops. Check the discharge line is clear and directed away from the building. If your basement flooding would be a serious event, that's the argument for a battery backup unit.
And the sixth, which you can't prevent — only prepare for: a sewer backup. It arrives from outside your control, and the only useful preparation is knowing to stop using every drain in the property immediately and to keep people and pets clear of the affected area.