Heterotrophic Plate Count (HPC), formerly known as the standard plate count (SPC) is a direct quantitative measurement of the viable aerobic and facultative anaerobic bacteria in water, measuring changes during water treatment, and distribution. The test gives an indication of the effectiveness of disinfection as well as the existence of cross connection and other problems within the distribution line. Total bacterial densities greater than 500 to 1000 organisms per ml may indicate coliform suppression. The pour plate method is simple. Each colony that develops in the agar medium originates theoretically from one bacterial cell. The spread plate method causes no heat shock, all colonies are on the surface and they can transfer quickly and easily. However, this method is limited by the small sample size, 0.1 to 0.5 ml that can be absorbed by the agar.