- ENGINEERING INFO
- CASE STUDIES
For decades, the City of Pleasanton, California has struggled with its potable water service line materials. The City transitioned from copper service tubing in the late 1970's to what was thought to be a less expensive, non-corrosive option in polybutylene plastic service lines. Within a decade or so, polybutylene was determined to be anything but a long term solution due to degradation of the material in the presence of chlorine-based water disinfectants.
In the early 1990's the City transitioned from polybutylene to polyethylene service tubing (making the switch from one polyolefin material to another). Fifteen to 20 years later, the City began experiencing polyethylene service line failures similar in nature to the previous polybutylene failures.
Potable water service lines represent the last piping connection between the City’s water distribution system and the water meter. This often overlooked link in the distribution system is the final step in delivering water to customers and revenue to the City. Seeking a solution to its systemic service line material performance issues led Pleasanton to ServiceGuard® Composite Pipe.
ServiceGuard® Composite Pipe utilizes a plastic material (chlorinated polyvinylchloride, or CPVC) that is very familiar to the waterworks industry and comes with a long track record of service in extremely oxidative environments. ServiceGuard® Composite Pipe is a CPVC-Aluminum-CPVC composite pipe, with three material layers that make up the pipe wall. The CPVC outer layer resists environmental and soil corrosion, which is often cited as the primary failure mechanism for copper service piping. The inner CPVC layer resists oxidative degradation from chlorine-based disinfectants, including those commonly used in potable water treatment. Finally, the middle aluminum layer provides strength, rigidity, and “bendability”, resulting in a water service line that behaves and couples much the same way as copper service tubing.
Around 1990, Pleasanton transitioned from “dig and replace” service line rehabilitation to a trenchless pipe splitting or extraction method. The trenchless method reduces excavation and surface disturbance by as much as 95% compared to dig and replace installation. Reduced excavation significantly lowers the cost of each service line replacement. Unlike polyolefin service line materials, ServiceGuard® Composite Pipe has the tensile capacity to withstand the pull forces typically required with trenchless installation methods. Unlike plastic coated copper tube, the external CPVC layer of ServiceGuard® Composite Pipe can withstand the rigors of being pulled through the buried environment without being compromised.
Scott Petersen of the City of Pleasanton stated: "We've been pipe splitting and replacing polybutylene service lines since the early 1990's. Our existing ground conditions are problematic for copper tube, so the primary replacement pipe material available in the past was high density polyethylene pipe. The installation loading often overcame the limited tensile capacity of the HDPE pipe during the splitting process, breaking the pipe and limiting the benefits of the pipe splitting installation method."
"In addition, over the last five years we've begun to experience the first wave of HDPE service line failures that have been in service less than 20 years. The primary failure mechanism has been oxidative degradation - the same issue we experienced with polybutylene service lines."
"Recently, we were introduced to ServiceGuard® Composite Pipe. ServiceGuard® Composite Pipe provides the needed tensile strength for pipe splitting, is not subject to the corrosion that plagues copper tube in our soils, and does not degrade in the presence of common water disinfectants like HDPE. In 2014 Pleasanton piloted ServiceGuard® Composite Pipe for approximately 100 services. Since that successful trial period, ServiceGuard® Composite Pipe has become part of our city standards and is now our preferred pipe material for service line replacement. ServiceGuard® Composite Pipe is currently being utilized for the 175 - 200 polybutylene and polyethylene service replacements that are slated for our 2015 capital improvement service line replacement project."
|Pipeline Details and Project Summary|
|Utility Owner:||Pleasanton Public Works|
|Program Summary:||More than 100 services replaced, with ongoing installations|
|Pipe Size:||1" Copper Tube Size (CTS)|
(1) United Facilities Guide Specifications (UFGS), latest version, May, 2013. Division 33 - Utilities, Section 33 11 00 - Water Distribution. Part 2 Products, 2.1 Water Distribution Main Materials, article 4. http://www.wbdg.org/ccb/browse_cat.php?c=3.
(2) American Water Works Association Research Foundation, "Water Utility Experience with Plastic Service Lines." Denver, CO, 1992. ISBN 0-89867-616-9.
(3) Water Research Foundation, "Chemical Permeation/Desorption in New and Chlorine Aged Polyethylene Pipes." Project # 4138. Denver, CO, 2010. © 1996-2012 Water Research Foundation.
The name Scott Peterson does not imply that Scott Peterson endorses this product or service in his official capacity and does not imply an endorsement of any governmental entity.