The study proposes a simple method for estimating the performance of different water-saving toilets in conveyancing experimental waste substitutes into the horizontal drainage piping (in terms of conveyor distance and the number of elbows) for apartment houses, and discusses the effectiveness and applicability of the method through demonstration on 15 different water-saving toilets. In the study, the fixture discharge characteristics of each toilet were calculated by using a simulation model and clean flush water. A conveyor distance was then estimated by collating the calculation results with the average fixture discharge rate, which was determined, in a performance of conveyance experiment, as a conveyance limit value, and the estimated conveyor distance was compared with the actual measured conveyor distance to verify the estimation accuracy.