The deterioration of urban water supply infrastructure is a significant economic issue. As the integrity of an aging infrastructure decreases, the loss of finished water in the distribution system increases. The loss of integrity in the distribution system is evident by the increasing amounts of reported breaches in distribution systems. Improved water is a commodity, therefore loss of improved water in the distribution system results in direct loss of revenue.
The economic losses attributable to breaches in a water distribution system are compounded by the increased supply of treated water required to meet demand and the cost associated with repair and replacement during a breach. The American Water Works Association (AWWA) estimated in the Distribution System Inventory, Integrity and Water Quality publication that there are close to 237,600 water main breaks per year in the United States leading to approximately $2.8 billion lost in yearly revenue.
Ideally, no water would be lost, however this not achievable in the field. There is a point at which it costs more to locate and fix leaks than is economically justifiable. A balance must be maintained between water loss reduction and costs associated with water loss reducing measures. A leak for 10 days at 1,000 liters a day represents a loss of 10,000 liters. A smaller 10 liter/day leak for 1,000 days (around 2 years and 9 months) has a comparable loss. Prioritizing investment for the greatest return requires careful consideration of available options. A water provider can directly affect real water losses by controlling:
- Pressure management
- Speed and quality of repairs
- Active leakage control
- Selection of pipeline and related assets
Pressure management affects water loss rates. Also, the lack of pressure management has been shown to increase pipe failure rates. These are relatively intuitive ideas since more pressure means greater flow whether it is through the pipe or through a crack or hole in the side of the pipe. Higher pressures mean higher stresses on the pipe. Higher pressure also means higher pressure spikes during pressure surges. These higher values translate into increased failure rates. The management goal is to meet customer pressure expectations, fire flow requirements and adequate pressures to operate the system at as low a pressure as is reasonable.
Technologies that absorb pressure spikes, such as SAVCO’s AquaSphere, have effectively reduced the frequency of water main breaks. Pressure surge protectors may be added to a system during a water main break at minimal incremental cost. As breaks are repaired and additional surge suppressors are added to the system, the shock protection increases exponentially. Within a very short period of time, often within one year, the cost of adding pressure surge protectors to a water supply system can pay for itself in reduced water main break repairs alone.
Water systems with one or more of the following traits should strongly consider water surge protectors:
- Higher than average annual break frequency (more than 25 breaks/year/100 miles of pipe).
- Larger percentage of older, cast iron pipes throughout the system.
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