Why do frozen water pipes burst?

Bursting water pipes is a year-round threat to homes, but in the winter, temperatures drop below freezing, and frozen pipes always burst. But why do frozen water pipes burst?

It’s all about internal pressure
The reason behind burst pipes is directly relates to the internal pressure within the pipes. If there’s too much pressure within the water pipes, the water (and pressure) have nowhere to go — and pipes explode.

The science behind bursting frozen pipes
Think back to your high school chemistry classes. During the freezing process of water, H2O molecules assume a different pattern. Freezing (and then frozen) water in this new state — what we know as ice — takes up MORE space in the pipe than in liquid state (flowing water). To put it simply: water molecules get bigger once they freeze.

When freezing water begins to expand, the water (in all states) gets pushed toward the appliance (e.g., faucet, toilet, etc.). Between the ice build-up and the appliance, there is an increasing amount of water pressure building up. At this point, things get even riskier.

Pipes to be most careful about are those that are exposed outside of your home, those that don’t have a covering, or those that are are unheated in some way. And yes, in many instances, your basement counts! Bottom line — if any of this occurs, you don’t want your water pressure to increase and risk burst lines.

At risk for frozen pipes?
If you’re at risk for frozen pipes in your home, and don’t yet have the time to properly insulate them, follow these tips:

  • Try slightly dripping the faucet to mitigate freezing
  • If you see reduced water pressure, it could be a sign of freezing
  • Check the water pressure once in the morning and once before bed
  • Check pipes adjacent to the water meter, including unheated and uncovered sections left vulnerable to freezing.

Click here to read more about how to protect your home from frozen pipes.

Sources:
http://www.livescience.com/43408-why-do-freezing-pipes-burst.html
https://www.allstate.com/catastrophe/pipes-freeze.aspx
https://www.iccsafe.org/wp-content/uploads/DIS-FreezeBurstPipe.pdf
http://www.csmonitor.com/USA/USA-Update/2015/0219/Preparing-for-an-Arctic-blast-How-to-prevent-your-pipes-from-freezing
http://www.nola.com/homegarden/index.ssf/2014/01/you_know_the_drill_run_the_pip.html