Water inlet pipes and inlet collar plates contained defective welds that failed on the tank bottom. The tank was originally emptied for interior re-coating and minor improvements. Minor improvements to the tank included welding a pipe extension to each inlet pipe to modify the inlet flow and create silt-stops above the tank bottom. The weld failures occurred as the tank was re-filled with water after a cleanout. The water in the tank emptied rapidly through the openings and created voids under the tank. The failed welds on the inlet pipes were repaired a second time before refilling the tank.