Ageing infrastructure in the waterworks sector is the leading cause of global water loss. A World Bank study reported that more than 32 billion cubic metres of treated water is lost globally every year through distribution system leakage. That’s an annual cost of over £10 billion – a problem worth solving. However, every utility has budget constraints and needs to ensure they prioritise their spending based on solid data.
Here, two industry experts, John Lamica from a US water authority and product engineer Cody Snell are asked how utilities can best make the decision whether to repair or replace water infrastructure.
Most water utilities are dealing with the problem of ageing infrastructure. To address this issue, many utilities prepare capital improvement plans based on the design life of pipes. Is there a more cost-effective way to deal with this problem?
JOHN: There are various ways that we determine whether a pipe needs replacement or repair. Multiple failures in the same area are a sign that that area is failing, so we might put that area under review for the capital improvement plan for replacement. We also use new technologies to complete the physical assessment of pipeline. We’ve been having problems with the failure of older pre-stressed concrete pipe. With today’s new pipe assessment technology, we were able to pinpoint specific areas where corroded pipe walls needed replacement. We’ve also used technology to help us find leaks. Basically, we use a combination of technology and internal system knowledge for capital planning.
CODY: To make the best use of limited resources, utilities should use an approach driven more by data and technology. Keep good records and note the frequency of leaks. There’s great technology available to assess the condition of pipes without causing service interruptions but in some cases they may still want to take physical samples of pipe. Acoustic condition assessment is a cost effective way for utilities to determine where to spend their money.
As noted, utilities monitor existing data on water breaks or pipe failures and assume the entire piping system in that area is about to fail. How can utilities determine the actual pipe condition and expose the pipe in various locations without disrupting a neighbourhood?
JOHN: Some years ago, we had pipe failures, one after another, within a mile. We usually dig back two or three pipe joints to look at the condition of the pipe. After the third failure, and because the 36”/DN900 line was a safety issue, we decided to replace the entire line. However, we’re also looking at some of the new technologies that help determine pipe condition without digging.
CODY: Acoustic technology has come a long way in the past few years. By using sound waves, we can employ technology aboveground. We can set up sensors on fire hydrants: typically, 300 – 1,000 feet/100 – 350m apart. Then we use acoustic technology and advanced computer algorithms to estimate overall pipe wall thickness. These segments give us a very good window into the overall condition of the pipe, and the ability to target problem areas.
How can acoustic technology measure pipe condition?
CODY: It’s based on the science of the way sound travels through pipe. Over time, as pipe deteriorates, the way the sound travels will change. As it changes, we can analyse data we are already familiar with to determine how much of the pipe wall is left.
How can acoustic data be used to determine the remaining life of a piping system?
JOHN: It’s fairly new technology, and I’m excited about it. I’m waiting on a report on this technology being done for the City of Marietta (Georgia). That will give me a good feel for how the technology’s working. Basically, acoustic data is used to extrapolate future pipe life based on the current pipe age and condition. It can estimate the amount of corrosion per year, so we can then determine how many years of pipe remain.
CODY: Sound, as it travels through the pipe, will slow down as the pipe wall degrades. Using that information, we can determine that there is more degradation in one area of the pipe versus another. This is better than relying on where pipe leaks are found, as many factors can cause leaks; improper installation, pipe damage, or other issues, not representative of the entire pipe, may cause leaks. With acoustics, we can identify specific areas where pipe degradation is occurring.
Can leaks be detected during a condition assessment with acoustic technology?
JOHN: Yes, they can. A problem I experienced in the past was that acoustic methods were designed for 16”/DN400 pipe and smaller. We have a lot of big pipe in our utility that the earlier technology couldn’t accommodate. The newer technologies now work on larger trunk mains.
CODY: Yes, that can be a bonus with a condition assessment. Leaks are identified very clearly with acoustic monitoring. As part of the assessment service, we also identify leak locations.
Does acoustic technology have limitations regarding type or size of pipe?
CODY: As with all technology there are some limitations, but those are really starting to decrease. Over the years, acoustic technology has greatly improved; the sensors and software are improved for more sensitivity. Now, leak detection can be performed on nearly every type of pipe reliably and pipe wall condition may also be assessed, including AC pipe. Pipe diameters from small service lines to 90”/DN2200 and larger pipe can now be monitored.
Is there a way to integrate data from acoustic technology with other programs to help utilities with asset management and capital improvement planning?
JOHN: I believe so. Technology is heading in that direction, and we have exciting opportunities now. Even in the last ten years, technology has improved tremendously.
CODY: Yes, when a condition assessment is done, we also provide Geographic Information System (GIS) data and other geographic data. This data includes areas with pipe wall degradation and leak locations. We colour-code the data on a GIS map — red for dangerous condition, yellow for degrading, green for good pipe. This makes it easy to see where pipe repair or replacement is needed. We can also provide raw data in Excel and other formats. This data can be pulled into a model to help prioritise which areas need repair or replacement.
What is the best way for utility managers to decide whether to repair or replace aging infrastructure?
OHN: I don’t know if there is a best way. In our oldest pipeline, we used a condition assessment tool to study the entire main — about 8-11Km. We only found five areas of pipe with defective joints. Instead of replacing the entire pipe, we repaired those areas for much less than the cost of a new line. Also, since the pipe was originally installed, new houses, buildings, and other infrastructure has been built, and replacing it would have been very disruptive. Eventually, the pipe will need replacement, but we’re able to get more life out of the system with the help of data from these newer technologies.
CODY: It’s important to prioritise, because you’re not just talking about the raw material costs. There are also labour and excavation costs that can be significant depending on the environment. For instance, construction in rocky soil or an urban area can be very expensive. You must look at the overall costs and find the best value for the utility. The results of an acoustic assessment can go a long way towards helping with that prioritisation.
For pipelines only needing repair, what types of product are most durable for extending the life of the system?
JOHN: Usually our problem with concrete pipe is due to corrosion of the pre-stressing wire from cracks in the concrete coating. We have plenty of adaptors for concrete to DI, so we replace failed concrete with ductile iron pipe. We do have a unique water system. We’re a wholesaler with big trunk mains providing water to other communities, and we have some unique problems. But we’re working more and more with some of the new technologies, which is very exciting.
CODY: Many products are available to the market. One big factor is how long the repair will be expected to last. For example: you have a new pipe with an isolated problem. The proper thing to do is cut out that section of the pipe and use full-body sleeves and restraint products to do a complete replacement. For an older pipeline needing a temporary solution, you may just need a product like a stainless-steel repair clamp. There are many varieties of those; they’re meant to be for temporary use. So, at some time in the future, they would need to be replaced either as an isolated incident or during a complete pipe replacement
About the contributors
John Lamica is Division Manager of the Cobb County Marietta Water Authority (CCMWA), a large regional wholesale water supplier in Georgia, USA, where water flows through more than 320Km of pre-stressed concrete and ductile iron (DI) pipe ranging from 16”/DN400 to 64”/DN1600 in diameter. Most of the original pipe was installed in the 1950s and 60s.
Cody Snell is District Engineer for Mueller Water Products, a company that has supplied products and services in the transmission, distribution and measurement of water systems for over 160 years.