Case studies have shown that leaks and other water losses in urban water distribution systems can account for 4-22% of total water demand. Detecting and fixing leaks and other losses can save significant amounts of water as well as embedded energy. Only a portion of these leaks are economically recoverable (estimated to be on average 40%). Approximately 870,000 acre-feet (AF) of water is lost per year through leakage via water distribution pipes throughout the state, and about 350,000 AF of this may be economically recoverable.
Cost and Energy Savings
Costs for leak detection and repair vary significantly based on the water system layout and age. Costs can run as high as $700/mile of pipeline for leak detection however costs vary by site. Surveys can be conducted at the rate of about 2 miles of pipe main per day. For a California leak detection program, half the savings were achieved with survey cost of less than $100 per acre-foot and 80 percent of the water savings were achieved with survey cost of less than $200 per acre-foot. Energy savings based on actual repairs can range from 17-27%. (see case study below)
Detecting leaks is relatively easy; fixing leaks economically is not always as simple. The percent of leaks that can be fixed economically varies by site. Specifically, the greater the avoided energy cost, the greater the percentage of economic leaks to fix, costs being equal. While not all losses can be fixed economically, the case studies indicate significant water intensity savings can still be achieved via leak loss detection.
Under the Embedded Energy in Water Pilot Program funded by the CPUC, Southern California Edison’s (SCE) Leak Detection Program sought to estimate real losses in three water agencies (Apple Valley, Las Virgenes and Lake Arrowhead) and estimate the energy savings associated with fixing those real losses that are “economic.”
The SCE Leak Detection Program estimated the real and hidden water losses in each agency’s system. Hidden leaks are the focus of leak loss detection and defined as leaks that are hidden from above ground, have a moderate flow and longer run times. The study analysts applied an Economic Evaluation of Leakage (ELL) model to determine the optimal level of intervention that minimizes total cost (annual cost of leak loss management + annual cost of lost water) to each agency. Energy savings were estimated by quantifying the energy intensity of each agency’s distribution system and relating it to the recovered water losses. The pilot estimated 17-27% pumping energy savings.