Freezing liquids and solids can exert as much as 2,000 lbs. of pressure inside water and sewer pipes.
Contrary to popular belief, pipes don't burst because of ice expansion. They burst because of the pressure build-up caused by the liquid trapped between the ice-freeze point and the closed faucet, spigot, or tap valve.
When water freezes, the molecules crystalize into an open hexagonal shape. This hexagonal shape occupies more space than when the molecules are in liquid form. So the molecules expand as they freeze.
This pushes the liquid trapped between the freeze and the valve toward the closed valve. Because of the tremendous amount of water pressure between the ice blockage and the valve, the pipe ruptures, usually at a spot where little or no ice has formed.
Typical vulnerable areas where pipes might freeze include:
- Pipes located outside of building insulation,
- Pipes located in unheated interior areas such as basements, attics, and crawl spaces,
- Sewer pipes with inadequate fall,
- Pipes that can't be buried deep enough below the freeze-line, and
- Pipes that must be installed in open air, such as oil transfer pipelines, stock watering units, and other industrial applications.
Each situation is different and, depending on your circumstances, may require different solutions. But, if you want to avoid digging up lawns, driveways, and parking lots or demolishing walls or basement floors, an internal pipe heater could be a great solution for the problem.
For more information on the types of pipe materials that can freeze, read our article on Why Frozen Water and Sewer Lines Break.