A good friend of mine went on vacation. When he got home he was horrified to find that a pipe joint had cracked, spraying water into the house for days. Lots of damage. Other ways this could easily happen:

1) Water heater rusts through
2) Supply line to washing machine bursts
3) Plastic pipe ruptures
4) (if its winter) pipe freezes and cracks
5) Etc.

An easy way to eliminate all these possibilities is to turn off the water before you leave. Most houses have a shut-off valve that is easily accessible in a downstairs closet or the crawlspace/basement.

[[[Jump to previous PSA - Sushi can give you tapeworms]]]