The NAHB Research Foundation released results of extensive testing on the performance of 49 of the most popular toilets in the U.S. Laboratory technicians measured flush performance, flush volume, trap diameter, water spot area and other characteristics. The study includes a couple of counterintuitive findings. One was no apparent correlation between price and performance. Another was that there is a considerable amount of variation from flush to flush with the same toilets. A report of the study and test results can be found at www.nahbrc.org or www.toolbase.org.
NAHB Surveys Toilet Flushing Performance