Testing concrete pipes is a critical element of utility efforts to develop cost management strategies and identify, repair or replace weak elements before they fail. NDT (non-destructive testing) uses sonic/ultrasonic techniques to conduct internal and external testing of concrete pipes to evaluate the structural integrity and identify pipe thinning due to internal hydrogen sulfide corrosion or external carbonization. Hundreds of miles of large diameter (48 to 120 inch) concrete water mains and hundreds of sections of concrete wastewater pipes have been evaluated using the impact echo technology. Internal sonic/ultrasonic impact echo and pulse velocity measurements are used to determine the integrity, strength, and condition of the core concrete and if broken pre-stressing wires have slipped and core concrete is delaminated from the cylinder. For wastewater pipes sonic/ultrasonic measurements are made on the exterior of an excavated pipe to determine if concrete core has thinned and weakened due to hydrogen sulfide corrosion.