Editor-in-Chief Elisabeth Lisican showcases a handful of features to read in the April 2017 issue of Water & Wastes Digest.
NRDC expert offers questions for water suppliers to use to evaluate the integrity of their water supply
Following the water main break that flooded the campus of the University of California, Los Angeles, Ed Osann, Natural Resources Defense Council (NRDC) senior water policy analyst, recommended water utilities ask the following questions to determine the vulnerability of their water supply:
1. How much water does our water system lose each year?
All public water systems lose water while distributing water to customers. The question is, how much? Most water main breaks don’t make the news. And even more water is lost from unseen leaks in buried pipes than from spectacular breaks that gush up through the pavement. If a spectacular break is just the tip of the iceberg, how big is the iceberg? Water utilities should be able to provide a specific estimate of the volume of water lost in any recent year.
2. How do we actually know how much water we’re losing?
It is impossible to literally measure the amount of water lost through each leak underground. A good method for estimating water loss has been adopted by the American Water Works Assn. (AWWA) in a publication called Water Audits and Loss Control Programs, Manual M-36. So, are we using the AWWA method to calculate and report water loss? If not, why not?
3. What do water leaks and water main breaks cost our water system each year?
Water losses add to the cost of running a water system, and thus have to be collected in the bills sent to all customers. These include the costs of pumping and treating the water before it is lost, and repairing pipes, streets, and sidewalks after a leak or break is discovered. Service may be interrupted to homes and businesses, which carries a cost. Damages may also stem from flooded basements and electrical vaults, submerged vehicles, or, in the case of UCLA’s Pauley Pavilion, soaking a newly laid hardwood basketball floor. So, how much did water loss cost our water system altogether last year?
4. Who pays for all the damages when a water main breaks?
A water main break is different from a natural flood or a hurricane—somebody is responsible. Water utilities usually cover damages through a mix of specific insurance policies and self-insurance. Insurance may cover various types of loss, such as traffic accidents involving utility vehicles or equipment failures at key facilities, as well as main breaks. So, what is our history of paid-out damages from water main breaks? And how much of this cost has been covered by insurance?
5. How accurate are our water meters?
Because water losses cannot literally be measured, a reliable estimate of water loss has to be inferred from quantities of water that are measured, i.e., the measured flow into the distribution system and the volume of water actually received by customers, as measured by their individual water meters. Understanding the accuracy (or inaccuracy) of customer meters is essential for estimating water loss. It is also important for alerting customers to leaks within their own premises. Unfortunately, most water meters have poor accuracy at low flows indicative of customer-side leaks, some of which may be hidden and run undetected for weeks or months. Industry standards have not effectively addressed the problem of meter inaccuracy at low flows, but some utilities are now showing interest in purchasing more accurate meters. So, how accurate are the new meters we buy? And what kind of testing is done to determine the accuracy of meters already in service?
6. What steps does the utility take to find and repair leaks before they become major breaks?
Many water main breaks begin as a small leak, and then work their way up to a catastrophic failure after running as an undetected leak for months or even years. Some utilities survey a portion of their distribution system each year to check for leaks using acoustical equipment or even video cameras. What is our utility’s leak detection program, and how much of our system is surveyed each year?
7. What is the average pressure in our water distribution system, and how is it managed to avoid unnecessarily high pressure?
Water travels through the pipes to our homes under pressure, and that pressure is managed by the water utility. Within a household, water pressure of between 20 and 80 pounds per square inch is considered acceptable by industry standards. Household appliances and fixtures can all operate well at the middle of this range, and higher pressure is really unnecessary. However, water pressure in the distribution system is far from uniform, due to topographic changes in the service area and the clustering of customer demands on the system. In some cases, the simplest way to get acceptable pressure to a few customers may be to provide unnecessarily high pressure to many more. The higher the pressure, the greater the volume of water that is constantly running out through unseen leaks, and the greater the vulnerability of weak spots to “transients”—short-term microbursts of water pressure that may be several multiples of the average system pressure. So, what is the average pressure of our water system? And how is our system managed to reduce unnecessarily high pressure and protect against transients?
8. How many miles of water mains are replaced each year, and at that rate, how many years would it take to replace the entire system?
It is common in many cities and towns to find water pipes in service today that are over 100 years old. Age alone is not the best predictor of failure, and some pipe materials have been found to degrade more quickly than others. Soil chemistry and even street traffic patterns can influence the durability of buried water pipes. But eventually, water system pipes need to be replaced, and there is not enough money in anyone’s budget to replace all the aging pipes in one year or even one decade. So, how much water pipe is being replaced each year? And is our present rate of replacement sufficient to maintain the reliability of our water service?
Share Your Answers
Water loss can move from a chronic problem to a civic emergency in the blink of an eye.
Thoughtful managers recognize that the public is largely unaware of the need for continual monitoring, assessment and preventive maintenance to reduce the waste of water and maintain the physical integrity of the water distribution system, and they are actually anxious to talk about it.