Water Use Efficiency
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Division of Statewide Integrated Water Management
Water Use Efficiency
901 P Street Sacramento, CA 95814-3515
P.O. Box 942836
Sacramento, CA 94236-0001
Leak detection is a necessary component to the management of water distribution systems worldwide. Accurate determination of the position of leaking water pipes within a supply system and subsequent repair serves to conserve water as well as energy. Water that is lost after treatment and pressurization, but before delivery to customers, is money and energy wasted.
Water Audit and Leak Detection
In the early 1980s, the Department of Water Resources conducted a survey with numerous water agencies to determine the amount of water lost from distribution systems due to leaks. The results of that survey indicated approximately 700,000 acre-feet of water are lost each year. In response, DWR prepared a guidebook in 1982 (Water Conservation Guidebook No. 5: Water Audit and Leak Detection) to assist water agencies with quantifying potential water loss due to leaks (Water Audit) and establishing a program to locate leaks (Leak Detection). The guidebook can be located at: http://www.water.ca.gov/wateruseefficiency/publications/
Additionally, the Urban Water Management Planning Act (California Water Code, sections 10610-10656) requires water agencies (as defined by the Act) to establish (if economically feasible) fourteen Demand Management Measures (DMM) for water use efficiency. The Water Audit and Leak Detection program is the DMM addressed in Water Code section 10631(f)(1)(c). For members of the California Urban Water Conservation Council (CUWCC), this is a Best Management Practice (BMP): http://www.cuwcc.org/Resources/BMP-1-Utility-Operations-Programs.
The Water Audit is an accounting procedure using agency data to determine water loss that may be due to distribution system leaks. The Water Audit requires the agency to determine an audit period and gather an assortment of data for that period. The guidebook defines the type of data necessary and provides worksheets as guidelines or for use in the audit. A simple Microsoft Excel Workbook, Water Audit Workbook (v2.0 2000) was developed by DWR and is available upon request. However, WC 10631(e)(2)(B) refers to the use of the AWWA System Water Audit Software, which can also be found at http://www.cuwcc.org/Resources/BMP-1-Utility-Operations-Programs.
Once an agency has determined the percentage of water loss and has performed a benefit-cost analysis to verify economic feasibility, a Leak Detection program may be established. The leak detection program is the field portion of the program. It requires knowledge of the layout of the distribution system and a good ear when using the sonic equipment. The Guidebook provides information on what steps are required to establish and perform a leak detection program.
DWR’s Regional Offices have leak detection equipment available for short-term loan to a water agency, and will provide assistance to local water agencies seeking to conduct a water audit and leak detection survey of their distribution system. Please contact the regional office in your area listed below for leak detection assistance:
|Northern Region Office:||Mark Riverafirstname.lastname@example.org|
|North Central Region Office:||James Briggsemail@example.com|
|South Central Region Office:||Steve Ewertfirstname.lastname@example.org|
|Southern Region Office:||Sergio Fierro||818-500-1645 email@example.com|
Leak Detection Frequently Asked Questions
How much water is lost to leaks?
Answer: A detailed water audit and leak detection program of 47 California water utilities found an average loss of 10 percent and a range of 30 percent to less than 5 percent of the total water supplied by the utilities. The July 1997 Journal American Water Works Association cites examples of more than 45 percent leakage.
Do leaks get bigger with age?
Answer: Yes. Leaks invariably get larger with time. A small leak this year will grow to become a large leak next year, all the while losing water and causing greater damage to infrastructure and property.
Does water from leaks always rise to the surface?
Answer: No, leaks are often unseen at the surface. Nonvisible leaks include leaks that percolate into the surrounding ground, leaks that enter other conveyance facilities, such as storm drains, sewers, stream channels, or old abandoned pipes. DWR estimates that up to 700,000 acre-feet of leakage occurs in California each year from nonvisible leaks.
What are the reasons to find and repair leaks?Answer:
- Leaks get bigger with age.
- Repairing leaks reduces growing water losses.
- Repairing leaks with regularly scheduled maintenance reduces overtime costs of unscheduled repairs.
- Leak repairs provide more treated, pressurized water to sell to customers.
- Leak detection and repair can reduce power costs to deliver water and reduce chemical costs to treat water.
- Leaks have been known to cause damage to nearby roads, other infrastructure, and sometimes buildings. Some water utilities conduct frequent leak detection and repair programs near unstable geologic areas to reduce their legal liability against expensive lawsuits.
- Leak detection and repair improves public relations. The public appreciates seeing that its water systems are being maintained.
- The utility gains credibility by putting its own house in order before asking the customers to conserve water.
How can I determine if there are leaks at my home or business?
Answer: Leaks from the pipes going to the building or inside the building lose water delivered through the utility meter and service.
There is one way to test if leaks exist inside the building:
- Repair leaky faucets, showers, toilets, etc.
- Turn off all the water using appliances (including the swimming pool, ice cube maker, water softener, etc.),
- Look at the meter. On the dial of many meters is a small triangle which rotates if any water passes through the meter. If this device is turning, then water is flowing to an appliance or a leak.
- You can also listen for the sound of leaks at the meter or at a hose bib.
What is Unaccounted-for-Water?
Answer: Unaccounted-for-water is a misleading term long used by the water industry. Unaccounted-for-water includes unmeasured water put to beneficial use as well as water losses from the system. Better terms distinguish between authorized unmetered uses and water losses. Authorized unmetered uses include firefighting, main flushing, process water for water treatment plants, landscaping of public areas, etc. Water losses include all water that is not identified as authorized metered water use or authorized unmetered use. Water losses are lost from the distribution system, do not produce revenue, and are unavailable for other beneficial uses. Examples of water losses are: illegal connections, accounting procedure errors, reservoir seepage and leakage, reservoir overflow, leaks, theft, evaporation, and malfunctioning distribution system controls.
Where does the water from leaks go?
Answer: Leaks often stay underground. The water may enter other underground facilities such as storm drains, sewers, electrical conduits, basements of buildings, or old abandoned pipes. Some water percolates into the surrounding ground, flows over the surface to stream channels, or evaporates.
What does leak detection cost?
Answer: Acoustic leak detection surveys can be conducted at the rate of about 2 miles of pipe main per day. The dollar cost will vary with local labor or consultant charges. For a California leak detection program, half the savings were achieved with survey cost of less than $100 per acre-foot and 80 percent of the water savings were achieved with survey cost of less than $200 per acre-foot.
What do leak repairs cost?
Answer: The cost of leak repair varies widely, from a few minutes by one person to tighten a nut on a leaky meter, to two days by a crew with heavy equipment to repair a deeply buried main. Scheduled maintenance for leak repairs is far cheaper than unscheduled overtime.
Why do leaks produce noise?
Answer: Leaks make noise because the pressurized water forced out through a leak loses energy to the pipe wall and to the surrounding soil area. This energy creates sound waves in the audible range, which can be sensed and amplified by electronic transducers, or in some cases, by simple mechanical means. Some additional noise created by the impact of water upon soil in the area of the leak. Agitated sand and gravel can sometimes be heard striking the pipe.