Why have there been so many water main breaks?

A flood of water main breaks in Topeka this year has left some local residents wondering about the system of pipes tucked beneath the surface of the city that carry clean drinking water to homes and businesses.

One reader asked #TopCity What? for a breakdown of materials and the schedule for replacement.

Topeka has about 870 miles of water lines, including 265 miles of transmission mains that carry water to storage towers and 605 miles of smaller distribution pipes, according to Braxton Copley, deputy director of utilities for the city of Topeka.

Most of the original water mains are cast iron, and some of those lines are still in service and well over 100 years old, Copley said. In the 1940s and early ’50s, the city shifted to ductile iron pipes. In the 1960s, polyvinyl chloride (PVC) pipes joined the mix of materials. The city moved away from ductile iron toward more PVC pipes in the past 15 to 20 years. Today, the city’s system of pipes is about 39 percent cast iron, 27 percent ductile iron, and 25 percent PVC, with the remaining made of various materials such as concrete and Transite.