16. WATER AUDITS AND LEAK DETECTION
Overview
Municipal water suppliers can save water and money by conducting system water audits to identify and address water losses in all aspects of the water system. Key components of an effective water audit program include:
- Regular system-wide audits to reduce unaccounted-for-water (UAW).
- Comprehensive leak detection surveys of water mains every 1-2 years and prompt repair of leaks.
- 100 percent metering of all water sources and end users to accurately track water flows and identify losses.
- A regular meter testing and replacement program.
- Water audits for residential and commercial customers.
UAW, a key measure of system efficiency, is defined by the Massachusetts Water Resources Commission as “the difference between water pumped or purchased and water that is metered or confidently estimated.” UAW includes: master meter inaccuracies, meter under-registration, estimation errors for stopped meters, over-registering meters, unauthorized hydrant openings, unavoidable or recoverable leakage, illegal connections, standpipe overflows, and data processing errors. Uses that can be confidently estimated and documented, such as known line flushing and known fire protection, can be excluded from calculation of UAW. All public water suppliers are required to calculate UAW as part of their Annual Statistical Report (ASR) to the Massachusetts Department of Environmental Protection (DEP).
The two major causes of high UAW are leakage and meter under-registration. Leaks can occur in water mains, service lines, and valves due to age, corrosion, and inadequate maintenance. Water suppliers should conduct comprehensive leak detection surveys of the entire water works system every two years and immediately repair all detected leaks exceeding three gallons per minute. The most common leak detection method involves the use of sonic equipment such as hydrophones to identify the sound of water escaping a pipe. Correlator devices can listen at two points simultaneously to pinpoint the exact location of a leak. Small leaks, when undetected for long periods of time, can actually lead to far greater quantities of lost water than large leaks that are detected and repaired quickly. Some leaks are not readily detected through sonic detection methods, so if UAW remains high after comprehensive surveys, alternative leak detection methods should be employed.
Meter under-registration should be addressed through programs to achieve 100 percent metering of all water users and aggressive meter replacement efforts. It is especially important and cost-effective to ensure that large commercial meters are well-functioning and accurate. Water suppliers can also offer free or reduced-cost water audits to residential and commercial customers, particularly large water users. The audits are designed to help users address leaks and reduce inefficiencies in their households, lawns, and businesses.
Local Examples
The “industry standard” for UAW is 10 percent, and many cities and towns in the Ipswich River watershed meet or come close to this standard, with UAW rates ranging from 5 to 18 percent. Lynn faces significant UAW challenges, with five-year average rates of nearly 24 percent, but has taken steps to address the problem by conducting a water system audit to reduce unaccounted-for water. Danvers has achieved excellent UAW results, with a five-year average rate around 5 percent, through the implementation of an aggressive leak detection program, including annual system-wide surveys. Ipswich identified and repaired a major leak that threatened the sustainability of its water system, and Reading has also made significant improvements. The city of Salem recently received a grant to conduct leak detection from the Massachusetts Department of Environmental Protection’s Water Loss Prevention Grant Program.
Several communities, including Salem, Ipswich, Reading, and Middleton, have offered water audits to residents and taken steps to replace old and malfunctioning meters with more accurate meters for large commercial users. For example, Middleton and Reading currently offer free in-home water audits by Energy New England auditors. A personal home profile is developed that illustrates estimated water consumption by end-use, compares that usage to similar residents in the same community, and itemizes steps to reduce water consumption. Wenham has offered technical assistance focused on reducing outdoor water use.
Resources
Ipswich Utilities, Water Leak Detection Survey, 1999 (pdf)
Reading Water Conservation Program (html)
Water Wise Communities: Index
- Introduction & Using the Handbook
- How Development Affects Water (link to IRWA site)
- Checklist: Is Your Community Water Wise?
- Water Wise Tools:
