I was selling a house in a state I no longer lived in, and was under contract to close the sale, when I got an email from the water company. It told me they suspected based on my water usage that there was a leak on the properly.

There had been a very cold February night (like -15F) and a pipe froze inside the walls, and it was just absolutely gushing out. They sent me the email after it had been leaking for a WEEK. I asked a friend to check it out and she said that the laminate floor went "squish" when she stepped in the front door.

Fortunately I was covered by homeowner's insurance since I could prove that my heat had been on, but that was a very unpleasant "warning" to receive!