When temperatures fall below 32 degrees, water pipes are at risk of freezing and bursting.
They can release several hundred gallons of water per hour, resulting in a big — and potentially costly — mess in your home.
Pipes burst because of the pressure that’s exerted when water freezes. It can exceed 2,000 pounds per square inch, so it’s no match for metal or plastic pipes. Ice particles can also cause problems in your pipes by blocking valves.
When temperatures are expected to drop into 20s, you should take the following steps to keep your pipes from bursting:

The Atlanta Journal-Constitution Things to do

NPR
Raw Story
OK Magazine
Gizmodo
NBC News NFL
AlterNet
America News