Why Do Pipes Burst?

And why do they always do it so uniformly?

frozen icy pipe

Frozen Pipe

Goran Zac. via Flickr, CC BY SA 2.0

When the weather gets cold, local news outlets start warning listeners about pipes bursting. But what exactly happens when water splits metal? Seattle engineer Nick Berry (who recently tested the limits of QR codes) wrote up a handy blog post to explain.

The answer comes down to how water reacts at different temperatures. As water freezes, the molecules crystallize into a hexagonal form, which takes up more space than molecules in its liquid form. This expansion—which Berry notes can add 9 percent more volume—causes cool things, like floating icebergs, but also not-cool things, like flooded basements.

But this is only part of the conundrum: Berry also examines why pipes tend to split in the same manner every time. Surprisingly, it's the same reason sausages split the way they do. It all comes down to hoop stress and longitudinal stress within the pipe walls, which run around the pipe and up the pipe, respectively. For a thorough explanation of the physics, check out the blog post at Data Genetics.