Water loss is one of the most significant challenges faced by public water systems. Not only does water loss lead to financial problems for the system, but it can also contribute to health risks. Thus, it is important for public water systems to reduce water loss as much as possible. One effective strategy that can be used to reduce water loss involves improving the performance of flow meters.
Understanding Water Loss
Two basic types of water loss can exist within public water systems: real losses and apparent losses.
Real Losses
Real losses occur when water is released from the distribution system unintentionally. This most commonly occurs because of leaks, which may be present in distribution mains, storage tanks and service connections. Leaks can also occur when storage tanks overflow.
Apparent Losses
Apparent water losses occur when water is received by consumer but doesn’t generate revenue, either because of theft or an error. Either type of loss can be related to problems or inefficiencies with flow meters. For example, an accurate meter will help consumers and/or the water distribution itself identify leaks, which are the primary cause of real losses. Efficient metering can also prevent apparent losses by ensuring that all consumers are billed accurately.
How to Improve Meter Performance
Before attempting to improve the performance of flow meters, water supplies should begin by performing a comprehensive water loss audit. The goal of this audit is to determine how much of the water added to the system during the year is lost, either due to apparent losses or real losses. Having this information will allow the water supply to evaluate the effectiveness of any changes made to meter performance. Once the current amount of water loss has been calculated, the water supply can proceed by evaluating the current state of flow meters. Depending on the types of meters being used, water supplies may have the option of making repairs to existing meters or replacing them with new ones.
Repairing Meters
In some cases, public water systems may be able to improve meter performance and reduce water loss by making repairs to the meters that are currently installed. If meters haven’t been working properly, repairing them may address some of the inaccuracies and reduce water loss.
Replacing Meters
If meters are broken or outdated, replacing them is typically the best option. When choosing replacement meters, water systems can choose from several options, including:
- Velocity meter- Velocity meters measure the velocity of water moving through the meter in order to determine usage. These meters are fairly accurate a low flow rates, although some water loss can still occur.
- Positive displacement meter- Positive displacement meters are more accurate than velocity meters at low to moderate flow rates, but they are still not the most accurate meter available.
- Fluidic oscillator meter- These meters less likely to experience problems due to debris in the water system than many other types of meters, but water loss may occur at low flow rates.
- Ultrasonic meter- Ultrasonic meters are highly effective and won’t lose accuracy over time. However, they do require a significant amount of energy in order to operate.
- Compound meter- Compound meters can be used even in locations with highly variable flow, thus preventing water loss for all flow levels. However, compound meters may be susceptible to clogs.
- Magnetic flow meter- One of the most effective and durable meters on the market, the magnetic flow meter loses no accuracy over time and can measure low, moderate and high flows.
Regardless of the type of meter chosen, it is important to perform regular maintenance and repairs when needed in order to ensure the meter’s continued accuracy. After upgraded meters have been in operation for a significant period of time, public water system can evaluate their effectiveness by calculating water loss and comparing values to the estimates made during the initial audit.
Sources:
http://water.epa.gov/type/drink/pws/smallsystems/upload/epa816f13002.pdf
http://sensus.com/documents/10157/51976/sensus-building-intelligence-into-water-metering-white-paper.pdf/5bd14d08-6211-497c-9364-543f173605ce
http://www.wwdmag.com/meter-reading-products-automatic/drop-drop-water-loss-prevention
