Pilot-scale constant-rate and declining-rate direct filtration systems were evaluated for treating a high quality surface water, using two flow rates and alum or cationic polymer as the primary coagulant. Turbidity, particle count, and total coliform count were used to compare filtrate qualities. It was found that the effluent qualities for the two filtration schemes were the same-a results that disagrees with the conclusions of a previous study that used lime-softened groundwater. However, the results of the current study were consistent with those of past projects in that the rate of head loss increase was the same for both types of filters. (Copyright (c) 1986 Journal AWWA.)