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Here's Why Water Mains Break

Water main breaks can close down roads, damage property and lead to expensive repairs. But why do pipes break, and what can you do when it happens? The following can serve as a helpful guide as you seek to be proactive with your infrastructure and educate your customers.

A city’s water distribution system is made up of an interconnected network of pipes. These systems have large transmission lines that feed smaller distribution lines (the ones that lead to residents’ homes). A series of valves throughout a city's system controls pressure and flow. Water towers store the water until it's needed, then gravity brings it into homes and businesses. With so much complexity and so many pipes working to serve our communities, water main breaks can happen anywhere and at any time. Here's a closer look at why. 

Why do water mains break?

Water main breaks happen for a number of different reasons. Whether age or accident, pressure changes or corrosive soils, here are a five simple animations that illustrate why breaks happens.  

1. Excavation work

When contractors, utility workers or even homeowners dig into the ground, they can unintentionally strike water pipes with their digging equipment. It can happen with a tool as simple as a shovel or, more commonly, with heavy excavation machinery. The need for proactive research and careful construction cannot be overstated.

digging equipment
Digging in areas around water mains can cause them to rupture if impacted with digging equipment.

2. Pipe age and material

Older pipes are more likely to break. For example, water mains installed before 1980 were often made of cast iron. Cast iron can be brittle and doesn't expand and contract easily with temperature changes. When this happens, the pipes have a tendency to crack. There are also older sewer pipes that are made of clay. This material also breaks easily. Water mains today are often made of ductile iron or plastic pipes to proacitvely avoid issues such as these. If your pipes are decades old, it may be time to examine their status.

older pipes
As pipes age the likelihood they will break increase. Likewise, older pipes are often made of material that is more likely to break.

3. Pressure changes

The pressure inside a water main can change in a couple different ways. One of the most common ways is through temperature changes, sometimes called thermal expansion. As the ground around a pipe freezes and heats, the pipes expand and contract – sometimes causing a rupture. Pressure changes can also occur when fire hydrants are either opened or closed too quickly. This is called water hammer.

pressure inside a water main
When the pressure inside a water main changes, it can cause the pipe to burst.

4. Ground settling

Over time, as the soil around a water main settles it can stress the pipes running beneath the ground. If the ground settles enough, the stress can break the pipe.

Ground settling
Ground settling over time can cause water mains to break.

5. Corrosive soils

Some soils are corrosive and can eat away at pipes over time. This is especially common in iron and other metal pipes. Eventually the corrosion causes the pipe to break. It happens most often at pipe fittings or in pipes that haven't been properly protected from corrosion. The Ductile Iron Pipe Research Association (DIPRA) suggests polyethylene encasement as a popular, economic and successful method of corrosion control. Some communities have opted to use pipe made out of non-corrosive materials such as C-900.

Certain soils can cause pipes to corrode and break.

What can you do when pipes break?

There are a number of paths forward when water mains break and cause problems in a community. It's important to choose a consultant that offers a number of diagnostic and repair solutions, because each case is different.

There's the traditional remove and replace method involving digging up and repairing the broken pipe. There's also innovative methods like non-destructive testing and trenchless technology that repairs broken pipes without disturbing the ground around it. As you explore the best path forward based on your unique needs, we have a number of resources you can use to to proactively evaluate the state of your infrastructure, including the following free eBook. 

Related Content: Steps You Can Take to Identify, Limit and Prevent Inflow and Infiltration [eBook]

Bringing it all together

Water main breaks can disrupt communities immediately and sometimes for the long term. Digging deeper into why breaks happen and what your options when they do, or to prevent breaks, can lay the foundation for reduced costs, most proactive measures, and a fully engaged and educated community.

About the expert

Greg Anderson

Greg Anderson, PE*, is a civil engineering leader and senior project manager who specializes in municipal engineering. With more than 25 years in the industry, Greg understands the importance of educating communities on how their infrastructure works and providing solutions when improvements are needed. Contact Greg

*Registered Professional Engineer in WI