Detection, auditing help property managers save water
All pipes and fixtures deteriorate and decay with time. The older the system, the more vulnerable it is.
Corrosion and rust accumulation, differential settlement, the wearing away of seals and fixtures, dislocation of joints, vibratory damage, blockage due to clogging and simple wear and tear on valves and meters all contribute to the slow and inevitable decay of a water system.
The first step in solving for leaks is finding where it occurs, according to water conservation firm WaterSignal. Lack of monitoring can result in unaddressed problems accumulating to the point at which the integrity of the whole water distribution system can be called into question.
But it can be prevented with real-time monitoring of the system. Prevention allows a system operator to focus limited resources for maintenance and repair where they are most needed and cost-effective.
The largest financial losses that occur within a water system are the opportunity costs associated with non-revenue water. Non-revenue water, which is not the same as unaccounted for water, is defined as water that is delivered by the water distribution system but never makes it to paying customers. Potential end-users never see this water since it has been lost to the system via leaks, evaporation and drift or even poor record keeping by the water department.
Water distribution system operation, losses
City pipes themselves are made from a variety of materials, with older pipes typically made from materials that are significantly different than newer pipes. The oldest cast iron water pipes have been replaced with flexible ductile iron pipes and steel pipes, which, in turn, are often replaced by polyvinyl chloride (PVC) pipes—though very large diameter water mains are still typically made from reinforced concrete pipes. PVC is popular because it is inexpensive, durable, and resistant to corrosion.
Leak detection technology
A newly constructed water distribution system made with modern materials leaks very little at first. All piping systems wear out over time and develop revenue-stealing leaks.
The technology changes with time, but the procedures remain the same. These methods can be direct or indirect, internal or external. Indirect methods rely on statistical analysis of flow data and pressure reading. Direct methods require active physical detection of leak locations. Internal methods measure
the characteristics of the liquid flow (velocity, temperature, pressure), while external measures require sensors that listen for leaks outside the pipes.
Though there are many advanced and expensive leak detection technologies used by industries (especially the oil and chemical industries) to detect leaks in process pipelines, most of these methods are not applicable to finding leaks in buried water distribution pipes.
The key to minimizing water losses are regularly scheduled audits (performed at least annually, which should include annual updates of the audit’s extent and scope) and thorough analysis of data collected through real-time water monitoring. During an audit, there is an examination of both the accuracy and completeness of the water supplier’s records and data. These include billings, receipts, and meter readings.
The simplest method of performing a water audit is to measure water distribution during off-peak hours (such as from 2 a.m. to 3 a.m.). If the amount of water distributed during these hours of low water usage shows a steady increase over time, it is indicative of significant water losses in the system.
The International Water Association (IWA), in conjunction with the American Water Works Association (AWWA), has standardized the methods and terms used by water audits. This consistent methodology rationalizes the process and results in consistent performance indicators. The IWA and AWWA divide total system water supply into authorized consumption and water losses.
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