For environmental impact assessment, the Japanese leaching test (JLT) is frequently used in Japan. The grains in JLT are ordinarily smaller than 2.0 mm, but the grain size might be impractical. Therefore, this study investigated the influence of controlled clod size on the leaching characteristics of represented crushable waste; drinking water sludge (DWS). First, compaction tests were conducted using DWS. Second, batch and column leaching tests were performed using various clod size fractions of DWS. The Al concentration was analyzed to investigate the effect on plant growth. Consequently, 81 of DWS was crushed to less than 2.0 mm clod size by compaction, so the clod size in JLT is reasonable for environmental impact assessment of DWS utilization. Furthermore, results of batch leaching tests using clods smaller than 0.25 mm substituted for the maximum Al concentration in column leaching tests.