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Title:
Sewer Pipe Infiltration Assessment:
Comparison of Electro-Scan, Joint Pressure Testing and CCTV Inspection
Abstract:
Accurate location, measurement, and characterization of all pipe defects that are potential sources of water leaks in a sewer line are essential inputs for the cost effective design of inflow & infiltration/exfiltration mitigation projects.
During studies by the ASCE, electro-scan, joint pressure testing (JPT) and closed circuit television inspection (CCTV) were compared to evaluate their relative effectiveness of detecting pipe defects that were potential sources of leaks. These test methods were applied to 2,230 ft of mainline gravity sanitary sewer pipe.
The joint condition assessment comparison showed that:
The number of defective joints detected by JPT were within 4% of those detected by electro-scan, and both the JPT and electro-scan independently detected more than three times the number of defective joints than those detected by CCTV.
The joint by joint comparison between the joint condition assessment provided by the CCTV and JPT combined and electro-scan showed that the ratio of coincident test results to the total number of tests varied between 100% (perfect coincidence) to 72%, with an average of 87%.
The comparison between faulty service connections reported by CCTV and electroscan showed that electro-scan detected four times more defective service connections than CCTV. The electro-scan also suggested that these defects were generally considerably larger than those at the pipe joints.
Comparison of costs showed that JPT is 4 to 5 times more than electro-scan or CCTV and the all-up cost of electro-scan is significantly less than CCTV.
The study also showed that: electro-scan is as reliable as JPT and CCTV combined at 20% to 25% of the cost of JPT; and electro-scan is at least three times more effective at finding pipe defects than CCTV at significantly lower all-up cost than CCTV.
For a complete report, please visit www.ASCE.org for more information, or to order a copy of this, and other studies.
ASCE Field Studies
ElectroScan Pilot Study Guidelines.
WERF Abstract
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