This is a common home-safety trick, but the “upturned glass + piece of paper” setup is mainly meant as a simple visual indicator—not a guaranteed way to prevent problems.
The idea is:
- Place a dry piece of paper in the sink.
- Put an upside-down glass over it.
- Leave it untouched while you’re away.
- When you return, check whether the paper or glass has moved, become wet, or shows other signs of disturbance.
If the paper is wet, it can indicate that water entered the sink while you were away, potentially from a dripping or leaking faucet or plumbing issue. If the glass has moved or fallen, that can also alert you to unexpected activity or vibration.
However, it won’t detect every leak, particularly leaks underneath the sink or inside walls. Before a long vacation, it’s more useful to shut off the main water supply (if appropriate for your home), check faucets and pipes for leaks, and make sure appliances that use water are secure.
So, the glass-and-paper trick is best viewed as a cheap visual warning system, not a substitute for proper leak prevention.
