The operation of waste treatment plants is often complicated by an intermittent flow of toxic materials, known as shock loads, usually from industrial sources. These shock loads, containing high concentrations of pollutants, may upset biological activity, fail to be adequately treated, or disrupt treatment programs. Intermittent dischages may cause such wide fluctuations in concentrations at the plant that adequate treatment may not be obtained. The solution usually involves some type of holding tank,in which an attempt is made to reduce the extremes of concentration. The report describes an ideal equalization tank defined as one which would, following a shock load, produce a uniform effluent concentration. Since the mean of the effluent tracer pattern represents the theoretical detection time, the effluent pattern sought is horizontal for twice the theoretical detention time. It is shown that a triangular shape of constant depth with continuous discharge would produce ideal equalization. (Author)