On Thursaday, groundhogs the country over had their annual moment of glory (one wonders if they like all the attention, or would have preferred other professions). Per Wikipedia's tally, their weather predictions were split: Fourteen reputable groundhogs saw their shadows, forecasting six more weeks of winter, and 14 saw cloudy skies and therefore spring a-coming (Moscow's groundhog, Archi, apparently slept in).
So as to not be wildly disappointed (and, hopefully, pleasantly surprised), we're prepping for cold weather and snow. And not just emotionally—it's a good time to be sure the pipes in your house are ready for a drop in temperature.
As you know because of that one incident last summer with a beer in the icebox, water expands and pipes can burst. With potentially costly consequences. If your home isn't properly insulated—or if you live in a region that doesn't normally see freezing temperatures, like the South, where construction hasn't always accommodated for glacial weather—a drop below 20º F is worth prepping for.
Understanding how pipes freeze is the best way to be equipped: As temperatures drop, blockage (i.e., ice) can form along the inside length of a pipe, which pushes the unfrozen water towards the ends of said pipe with unwieldy pressure. (The best description I've read of this is that it acts "like a piston.") The result is often that pipes burst where they aren't frozen—downstream from that icy location.
So: By preventing that freezing in the first place (with thorough insulation), and also lessening pressure at the ends of a pipe, you can prevent the bust and resulting flooding. Here's how:
If you wake up to get a glass of water and there's none coming out of your sink's faucet, don't panic. Keep the faucet open and call your plumber! It's true that you can use a hairdryer to gently thaw the frozen section of the pipe, but it's best to have a professional check it out first—if a pipe has already busted and you just don't know it, thawing the ice inside will result in flooding.
Many thanks to my new best friend Justin, at JCA Mechanical Plumbing in Queens, who walked me through all these steps and made the very good point that attempting to thaw a frozen pipe can be a very bad idea indeed.