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Name:City Watermain Standards – DIP versus CIP <br />Date:March 31, 2026 <br />Page:2 <br />Document5 <br />in excessive deflection leading to potential weak spots in the pipe. DIP also handles freeze-thaw cycles <br />better and is more resistant to frost stress. <br />2. Ability to Locate Watermain <br />DIP has the advantage in this category due to the fact that it’s metallic and electrically conductive. The <br />material also responds well to electromagnetic locators and can be found by direct connection to a valve <br />or hydrant. To locate PVC, you need to rely on a tracer wire installed with the pipe. During construction, <br />there is a potential for tracer wire damage or the need to be spliced. The wire does not have the <br />integrity of DIP and can be damaged during backfilling operations or by soil movement. The wire also <br />needs to be daylighted so a locator can connect to it in a port and becomes susceptible to corrosion at <br />these locations due to climate conditions in Minnesota. Locating utilities is a legal responsibility for <br />municipalities and a very frequent task for the Public Works Department. Reliability within the <br />watermain system is paramount to being able to effectively locate lines. <br />3. Leak Prevention and Detection <br />DIP has more robust joints than PVC and is generally less prone to leak at a joint. DIP is also stronger <br />than PCV and more resistant to subsurface movement and pressures. Detecting leaks in DIP versus PVC <br />watermain differs significantly because of material behavior, joint type, and acoustic response. DIP has <br />the advantage in this category because leaks in this material produce high-frequency acoustic signatures <br />which can be detected by ground microphones and correlators. Leaks in PVC watermain tend to be low- <br />frequency or nearly silent, which can result in significant water loss and extensive damage due to the <br />time it takes to locate. <br />4. In-Place Water System Continuity <br />It is estimated that approximately 70% of the build-out of the watermain system in Lake Elmo has been <br />completed, which was done with DIP as the City Standard. Much of this work has been done in the last <br />25 years, so the pipe is still early in its lifecycle and replacement is not anticipated for several decades. <br />There have not been problems or performance issues with DIP and Public Works staff have the tools and <br />knowledge to maintain the system. Changing the standard now could create issues for staff when it <br />comes to utility locating, leak detection, and potentially managing system pressure zones. It is <br />recommended to continue using DIP in the absence of a significant factor to drive a change. <br />5. Cost <br />Recent bid prices for DIP and PVC watermain across different projects in the metro area have been <br />reviewed and generally PVC is approximately 15% - 20% cheaper than DIP. Various diameters of <br />watermain were analyzed and the lower pricing for PVC was consistently in that range. One item to <br />consider with construction is the way that pricing can change based on fuel prices, material shortages, <br />shipping interruptions, and other factors. Current prices are not guaranteed to remain consistent in the <br />future, but right now PVC is a cheaper option than DIP.