Pipes used in buildings for supply of hot and cold water, as well as of water for air-conditioning systems, are subjected to deterioration due to the various factors, which may lead to leakage and blockage of the pipes and to malfunctioning of the systems. Causes of the deterioration vary but one which has shown a rapid increase in recent years is the corrosion of the pipes. A typical example is the phenomenon of reddish water observed in galvanised steel pipes used for water supply. Reduction of inner diameters of pipes by and tubercles leads to increased frictional resistance in the pipes and is a factor that may render the whole systems unreliable. Under these circumstances, there has been an increasing demand for techniques, not only for the arrangement of pipes, but also for diagnosis of deterioration in water pipes in buildings. The present paper provides an outline of an automatic inspection system for piping corrosion, together with examples of diagnosis implemented using the automatic system.