A frozen faucet with a busted pipe.

Why Do Water Pipes Sometimes Rupture During an Extremely Cold Event?

Ever wondered why water pipes sometimes rupture during an extremely cold event?

Once water in pipes is exposed to below freezing temperatures, (32°F/ 0°C) for a period of time, ice formation will begin. Obviously, there are several factors that determine the freeze rate of the water. It relates to ambient temperature, wind speed, initial temperature of the water, conductivity of the pipe, etc. Eventually, if the pipe stays well below freezing for a long enough period of time, the water inside the pipe will freeze solid.

Water, unlike most materials that shrink when they are cold, actually grows in volume as the ice content increases. A volume of water that has been completely frozen will increase its volume as ice by about 9%. As an example, a gallon of water constitutes 231 cubic inches of water. If it were to freeze, the volume of ice would be close to 252 cubic inches! An increase of 21 cubic inches.

This increase in volume within a closed piping system can create pressures that exceed 25,000 psi.

The burst pressure of typical PVC and copper pipe is around 3,000 psi or less in some cases. The pressure required to rupture a PVC or copper pipe may be attained even before all the water within is completely frozen.

Steel pipe has a much higher burst pressure rating, but it can also rupture as a result of the water within freezing.

Ruptured pipes can create a multitude of serious problems, such as:

  1. Water outage to the end user for an unknown length of time.
  2. Whether repaired by the owner or a contractor, the cost to repair can be significant.
  3. Once ambient temperatures are above freezing and the pipe’s water is thawed, water loss thru the rupture can be significant as well as the possibility of the unchecked water discharge creating damage.
  4. And finally, the inconvenience to the homeowner. Until the pipe is repaired, the whole system has to be shut off until the damaged pipe has been repaired.