This paper summarizes Philadelphia Water Department's experience in representative sampling from the bodies of water in a drinking water system. The focus of this paper is on discrete grab sampling such as for basic quality control parameters (i.e., turbidity and bacteria, pH and temperature, total organic carbon and chlorine residual). Although grab samples provide only a snapshot of water quality at a point in the system, they remain very useful in that systems quality control. This paper also focuses on sample systems fed by gravity, as from an elevated basin, or by a pump as from a basin, or by a tap into a pressurized pipe.