Why do Pipes burst in the winter?

Why do Pipes burst in the winter?

Generally water pipes burst in winter season when the temperature of the outside atmosphere reaches zero degrees Celsius. The water freezes at zero degrees and if the material with which the pipes are made play an important role in the bursting of pipes. Water has the nature of expanding when it freezes. If the water expands in a closed vessel or pipe and if the pipe or vessel is not sufficient to harbor the expanded form of water then there is a chance of the pipe to burst open. This will give way for the ice to exist in expanded form.
The water expands in a closed environment and it causes intense pressure on the inner walls of the pipe. The pressure is exerted on the inner walls made of iron, lead or PVC plastic. Even if the pipe is strong to bear the pressure exerted by the expanded water, frequent exertion of pressure consistently can make the pipe to weaken gradually and burst at some point later.
Pipes that are exposed to cold air and which lack insulation in its walls begin to freeze inside even at 20 degrees Celsius. Water expands and occupies more volume when it becomes ice. The formation of ice will block the pipe and does not allow the flow of water through that part of the pipe. The ice block enhances the pressure inside the pipe by increasing the space it occupies. As the amount of water that freezes increases, the pressure that is built inside also increases. No more pressure can be tolerated by the pipe and there is no other chance for the pipe to withstand the pressure inside. Hence, it bursts to accommodate the ice and its required volume which is more than that occupied by water.
The type of pipes that are affected include hose bibs, sprinkler lines, swimming pool supply lines, crawl spaces, attics, basements and garages.