The Physics of Freezing Pipes

Burst Water pipes are causes by the expansion of freezing ice against the walls of the pipe, right? WRONG.
In a remarkable series of laboratory and field experiments, researchers at the University of Illinois have demonstrated that the actual cause f damage to freezing water pipes isn’t the force of the expanding ice on the pipe, but rather an extreme rise in water pressure downstream from the blockage. According to the study, the water pressure can rise in these situations from about 40 pounds psi (per square inch) to more than 4,000 pounds psi.


A typical scenario might go like this: A stretch of copper pipe is exposed to unusually cold temperatures, and ice begins to form on the pipe’s inside walls. Since water volume expands by about eight percent as it turns to ice, the ice formation eventually can completely block the water flow. Water upstream from the blockage is able to flow back to its source, such as the street connection. But the water downstream is trapped because the faucets are closed. As the ice continues to form and expand, pressures downstream from the blockage skyrocket. Because this entire section of pipe experiences the same elevated pressure, the failure can occur at any point, even within the heated space of the building.


Now that researchers better understand the problem, they have devised a simple, effective solution: a modified faucet washer that enables the faucet to leak a little under high pressure. This inexpensive device could eliminate much of the $400 million per year of insurance claims now paid to homeowners for freeze-related plumbing damages.


Source: Ned Nisson, Popular Science Magazine, February 1997


How to Prevent Frozen Pipes

Kentucky-American reminds customers that pipes may freeze anytime the temperature is below 32 degrees.


Your Prevention Checklist

  • Prevent Frozen pipes by taking these steps before cold weather set in:

  • Wrap exposed pipes with insulating material.

  • Block air passages into crawl spaces and basements.

  • Remove hoses from outside faucets and be sure to fix any leaky outside faucets.

  • Know where you shut-off water valve is located. This valve should be used in the event of a burst pipe or significant leak


Remember to follow these tips during freezing weather:

  • Keep meter box lids closed to prevent cold air from freezing the meter.

  • Make sure that heat reaches your pipes. If your pipes are in a cabinet under the bathroom or kitchen sink, leave the cabinet doors open so heat can get in.

  • Keep a trickle of water running during periods of low usage and particularly on sub-zero nights.

  • The trickle should be a steady stream the size of the lead in a pencil.


If you have a frozen pipe, you should:

  • Simply wait for the pipe to thaw, if at all possible.

  • Never use an open flame to thaw a pipe, since you could start a fire.

  • Call a plumber and get professional help, if all else fails.