Failure of a tubular heat exchanger made up of copper based alloys in a steam power plant was investigated. Tubes were made initially from yellow brass, and there after replaced by Cu–5Ni alloys. Circulating water from cooling tower was used as coolant, to condense the hot steam inside the steel shell. The velocity of cooling water was found to be very low, causing accumulation of deposits, reduction of diameter and some times complete blockage of tubes. The causes of failure were investigated performing various tests such as chemical analysis, XRD, optical, and SEM examination. Study revealed that tube material suffering from extensive dealloying and impingement attack.