Finding leaks early helps reduce the level of damage that a larger main break might cause. Leak detection also helps keep production costs down, which in turn has a positive impact on our customer’s water rates.
DMWW began its leak detection program in 1983. At the start of the program, DMWW’s unaccounted for water (total pumpage minus billed) was at 15 percent. Today, DMWW’s unaccounted for water is 7-9 percent.
Water Distribution’s staff performs an annual leak survey of the distribution system. In addition, leak survey and follow-up activities are conducted for other metro area communities, plumbers, contractors and property owners.
The leak detection team uses a highly sensitive electronic sounding device to listen for leaks. The leak surveyor systematically works his or her way through the distribution system sounding valves, blow-offs and hydrants, searching for leaks. When a leak sound is discovered, the leak surveyor records the leak in DMWW’s geographic information system (GIS) software. These leaks can be as small as pinholes in the pipe or as large as a split main.
Follow-up involves sounding the structures where a leak sound was found during the survey. The Field Service Technician must determine if the leak is actually on the valve, hydrant, or the main. A leak correlator and outstation sensors are used to run scans on the water main to pinpoint the location of a leak. The leak can usually be pinpointed within one to two feet of its actual location. Identified leaks are then turned over to a repair crew.
Advance pinpointing of leaks and main breaks saves Des Moines Water Works $30,000 to $50,000 each year in labor costs.