The distribution system's efficacy and reliability are greatly affected by the water quality in the pipelines. It is common practice to measure water's scaling or corrosive potential using the Langelier Saturation Index (LSI). The most common issues with drinking water facilities caused by corrosion and scaling include water loss, reduced facility life, pipe punctures, pipe clogging, and pressure loss in distribution systems. This paper aims to develop equations for calculating the pipe mass loss due to pipe corrosion that is subjected to water characteristics of PH, alkalinity, calcium hardness, TDS, and temperature, which give negative LSI indicators. Ten identical samples, five ductile iron sheets and five carbon steel sheets with dimensions of 5 x 3 x 2 cm were subjected to water with LSI indicator values of -0.2, -0.5, -1, -3, and -5. The sheet mass loss was recorded every seven days. Two equations for the two used pipe material types were developed to calculate the mass loss for any LSI indicator value at a given time. It was found that the mass loss due to pipe corrosion for ductile iron pipes was less than that of the carbon steel pipes.