About the author: Hubert Colas is president of the Americas for FluksAqua. Colas can be reached at [email protected].
Water loss affects every water system in the country, but only a handful of states actually track it. Gathering data on losses means water professionals can get a handle on the problem and take steps to solve leakage issues.
Texas is one state gathering information on water loss with a goal of making systems more efficient. An analysis of the most recent data by FluksAqua shows that the state lost the equivalent of more than 155,000 Olympic swimming pools worth of drinkable water last year at a cost of $400 million.
Dan Strub is conservation program coordinator for the city of Austin, Texas, and has spent the past seven years working on reducing the city’s water losses. The decision to invest in reducing water loss was driven by three factors: drought, environmentally conscious residents, and the utility’s desire to be responsible with a vital public resource.
Establishing DMAs
Some solutions were simple. Austin Water tightened up data practice areas to concentrate on water loss. It also rearranged field crew schedules, creating day and evening shifts. The number of employees did not change, but having crews available later in the day meant issues could be addressed more quickly.
The city also reviewed tracking and reporting of unmetered water usage by other city departments. The fire, streets and bridges, resource recovery, and watershed protection departments all had access to fire hydrants and would open them for various reasons at no cost. The water utility started billing for this usage, with the exception of water used for fighting fires.
Many municipalities have looked to district meter areas (DMAs) to help in reducing water loss. DMAs are small zones that usually include about 1,000 to 3,000 customer service connections and are formed by closing valves to create a boundary. There is at least one measured or metered supply pipeline left open to send water into the DMA so it is not entirely disconnected from the system. By establishing a small area within a city or town, water professionals can monitor flow rates more easily and identify leaks more quickly.
The decision to invest in reducing water loss was driven by three factors: drought, environmentally conscious residents, and the utility’s desire to be responsible with a vital public resource.
Once local DMAs are established, a baseline needs to be calculated, which can mean completing an acoustic leak detection survey to identify existing leaks and then repairing them. The goal is to remove the backlog of existing leaks and bring the flow into the DMA down to a baseline level that reflects the supply needed to meet customer demand in the area. The baseline is used for monitoring purposes going forward.
While some calculations can be made using existing information, each DMA is unique, especially when it comes to cost. There may be times when repairing a small leak will cost more than the water lost once the cost of dispatching a crew and digging up and repairing the leak is tabulated. The cost of a small leak under a major roadway may not justify the repair. So both the cost of the water being lost and the cost to repair a leak should be considered. These two numbers will be different for each system.
The typical flow rates into the DMA should be small enough that a new leak produces a discernible increase in flow. This allows a municipality to then strategically send leak detection personnel to the DMA to pinpoint and repair the leak. When input flows are within the normal range, leak detection crews do not need to be deployed and crew time is not wasted.
Municipalities considering DMAs should conduct pilot testing before rolling them out across the entire system. The city of Austin is starting to pilot test DMAs with former wholesale customers where there is one master meter. This allows the area to be compared to other customer readings.
“There were some months where the water losses in a pilot DMA were 40% higher than other areas, so we were able to clean it up and bring it into line,” Strub said. “But DMAs do have their limitations, so we are introducing them where they make sense. In places like England, they are easier to introduce, because their water system is like a tree with branches. Water infrastructure in the U.S. is more like a spider web, so creating small areas to meter can be an expensive proposition.”
Trickle-Down Effect
Austin uses the Infrastructure Leakage Index (ILI) as a performance indicator of physical water loss from the supply network of water distribution systems. Austin’s ILI hit 2.0 in 2012; the target was 2.7. But Strub admits it ticked up to 3.88 in 2016.
“The increase is unexpected, but it means we have to look at how to analyze the system and what tools we can use to determine where the leaks are actually happening,” Strub said. “Our best guess is a leak in a transmission main, so it is not surfacing. Now we are investigating to confirm our theory.”
Austin is situated on porous Karst limestone, so lost water does not necessarily pool. Water loss also is hard to determine because of the depth and acoustics of the transmission line. Austin Water is investigating with new acoustical sensors and satellite technology, which can detect potable water leaks from above.
“The satellite will be able to detect a plume of water from above, so if the leak is from the main transmission line, we will be able to see it,” Strub said.
Beyond managing leaks more efficiently, being proactive has a trickle-down effect on a water system. First, there is less property damage because leaks are caught earlier. Second, water conservation means there is more in the system, so new homes can be connected without the need to construct new transmission mains, pump stations or treatment plants. It means more accurate and timely water use data without needing special flushing programs.
Many people take clean, safe drinking water for granted, but water is a valuable resource and the investment should be made to ensure systems are maintained and improved. Each state should gather data on water losses so water professionals can work to stop the waste.