Water main breaks don’t happen every day (thank goodness), but when they do, they can cause a massive amount of destruction and chaos. Whenever you hear about a water main break on the news, chances are it affected traffic. However, water main breaks can happen anywhere and anytime, including in small, rural towns and big cities.

What is the Cause of Most Water Main Breaks?

Whether you’ve recently heard about a water main break on the news, or you’ve experienced one yourself, you might be wondering what causes the water main break to occur. Although there are several factors that can contribute to water main breaks, the following reasons are the most common.


The most common cause of water main breaks is age. The older water main pipes are, the more likely it is that they’re going to break. Why? Well, because just like anything else, as pipes age, they become more brittle. As such, the water pipes are more susceptible to damage and prone to breaks. In Manhattan, for example, the average water main is 66 years old; hence why these calamities seem to happen a more frequent occurrence in the Big Apple.

Freeze-Thaw Cycles

Another major factor that can contribute to water main breaks is freeze-thaw cycles. Big temperature fluctuations – especially if those fluctuations occur suddenly (hot to cold or cold to hot) – place additional stress on underground pipes, which are already strained. When the ground freezes around the pipes, pressure in the soil increases, and as such, the pipe can burst.

A dramatic change in the temperature of the water that flows through the pipes can also create a shock effect. When the water freeze, for example, it expands, causing the pipe to expand too. As the pipe expands and contracts, it can crack, leading to a water main break.


Water mains experience a lot of wear and tear, both on the interior and exterior of the cast iron pipes. The water that travels through the pipes contains minerals, and over time, the minerals can corrode the interior of the water lines. Furthermore, the soil that surrounds the pipes can be corrosive in nature.

For instance, if the soil is acidic, it can corrode and weaken the pipe. When a water main experiences either interior or exterior corrosion, it could eventually break. If both the interior and exterior of the pipe corrode, the chances of a water main break are even higher.

Shifting Soil

The earth is always moving, and as it does, the soil shifts and moves, too. As the soil shifts, pressure is applied to underground pipes. When conditions are unusually wet or dry, the soil shifts even more, which can undermine the bedding that the underground pipe rests on, causing greater pressure to be applied to the pipe.

Other factors that can contribute to shifting soil that can lead to water main breaks include earthquakes and tremors, aftershocks, heavy machinery, and equipment movement. Even the growth of old trees and their roots can influence the settling effect on the soil, thereby increasing the risk of a water main break.

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