Non-revenue water–The sum of unbilled authorized consumption (firefighting, etc.) plus apparent loss (meter inaccuracies and unauthorized consumption) plus real loss (leaks).
—the International Water Association and the American Water Works Association
Water loss is serious business. Whether the loss is due to leaks, theft or mis-sized meters, identifying the source of non-revenue water (NRW) is the first step to reducing it. The District Metering Areas (DMA) feature can help in this regard.
Identifying Real Water Loss
The following Consumption Graph shows a real-world DMA zone with 1 Supply Meter and 19 Demand Meters. (Supply Meters measure water flowing into a zone. Demand Meters measure water being consumed within a zone.)
As you can see, Supply Meter consumption (in dark blue) outpaced Demand Meter consumption (light blue) between January and July. Over time, the difference increased. That difference represents real water loss from leaks or supply tank spillage.
Hovering the cursor over each point on the graph lets you see more details by displaying the total consumption, difference and percentage change between the Supply Meter and the Demand Meter consumption at that point in time.
In January, the difference between Supply Meter and Demand Meter consumption was -2,090 gallons.
By July, the difference was -1.3 million gallons.
NRW by the Numbers
In the popup displays, the difference between Supply Meter and Demand Meter consumption along with the percentage change in parenthesis are calculated in the following manner:
Percentage = ( later value – earlier value ) / earlier value
S = the volume measured by Supply Meters (earlier value)
D = the volume measured by Demand meters (later value)
Difference: D – S
Percentage: ( D – S ) / S
When the total consumption of your Supply Meters is greater than the total consumption of your Demand Meters, take the following action:
- Verify that all of the Demand Meters fed by the Supply Meters are actually included in your DMA zone.
- Perform further analysis by exporting hourly data for the period where water loss is at its peak. Based on that analysis, inspect the most likely culprits, for example, your storage tanks and the lines that feed your Demand Meters for possible leaks.
Water Loss and Metering Inaccuracies
Mis-sized meters represent another source of non-revenue water.
The Consumption Graph below shows a DMA zone with two Supply Meters (dark blue) and 697 Demand Meters (light blue). Because Demand Meter consumption is greater than the Supply Meter consumption, the Supply Meters cannot or are not accurately measuring the volume of water flowing through them. Potential causes include meter size and meter resolution.
To troubleshoot this particular example, use the DMA Zones>Supply filter to display the cards for each of the Supply Meters. Expand the cards and look at the size of each meter, which in this example is 12”. A 12” meter is capable of supporting flows of up to 7.9 million gallons per day, a volume well below the volume shown.
That raises the question, “How can the Demand Meters draw more water than is being reported by the Supply Meters?” The answer is that larger meters typically fall short when measuring low flow. That is, flows that would be easily be detected by smaller meters go unmeasured by larger meters.
When the total consumption of your Demand Meters is great than the total consumption of your Supply Meters, take the following action:
- Verify that you did not inadvertently omit Supply Meters from your DMA zone.
- Export hourly data from across the DMA zone and analyze the minimum nightly flow total for all of the Demand Meters in the zone.
- Determine whether your Supply Meters are capable of measuring the minimum nightly hourly flow data consumed by your Demand Meters. For example, if you find that the minimum nightly flow is 10 gallons per hour, determine whether your Supply Meter is capable of measuring 10 gallons per hour.