One of the biggest challenges water system owners face is replacing their aging infrastructure steadily to stay ahead of the facility’s life span. After all, replacing an old water main during a scheduled replacement program is better than having an inconvenient water main break in the middle of winter. However, it can be daunting when considering the miles of pipeline in a system and the limited funds available. How do you prioritize which water mains should be replaced first? Below are some items municipalities should consider when planning their next water main replacement project.

Age and Size of Water Main

It’s common to find 100-year-old water mains and valves still in service. Old cast iron water mains typically have problems with corrosion that can lead to breaks, customer complaints of poor water quality, or tuberculation (scaling) on the inside of the pipe. An 8-inch water main may only function like a 6-inch water main or smaller if internal corrosion has constricted the flow area and increased the roughness coefficient of the pipe. Small diameter and corroded water mains may not provide the required fire flow and should be upsized to meet system demands.

Old water mains often have shallow bury depths due to a lack of frost depth information or limitations of construction equipment available at the time of installation. In colder climates where at least 6 feet of cover is recommended to prevent freezing, some water mains only have 4-to-5 feet of cover. These water mains should be replaced with sufficient cover to prevent freezing.