Pipe dreams

Well, it's about to get really cold tomorrow night, and I'm hoping to keep the pipes on my house from freezing. It's going to be tricky, because I have so many leaky valves and faucets that it will be difficult to keep water dripping from the faucets.

So I was wondering, how cold does it have to get before there's likely to be a problem? About 20 degrees Fahrenheit, according to this page provided by the Newton BBS of the Argonne National Laboratory. The page--well worth reading in its entirety--includes this fascinating information:

When water freezes, it increases in volume about 9%. The ice then shrinks as the temperature decreases. The shrinkage is tiny, about 0.4% going from 30F to -50F.

As a side note, liquid water is densest at a temperature of 39.2F. The density differences at higher and lower temperatures are very tiny.
Cooling 39.2F water to 0F expands it only 0.01%.

Another note, there are at least 12 forms of ice. Most can be obtained only in the laboratory under high pressure.

The American Red Cross provides a page with practical information on Preventing and Thawing Frozen Pipes.

I'd better get cracking here, so that my pipes don't...