Why Pipe Freezing is a Problem Water has a unique property in that it expands as it freezes. This expansion puts tremendous pressure on whatever is containing it, including metal or plastic pipes. No matter the strength of a container, expanding water can cause pipes to break. Pipes that freeze most frequently are: Pipes that are exposed to severe cold, like outdoor hose bibs, swimming pool supply lines, and water sprinkler lines. Water supply pipes in unheated interior areas