On Sept. 28, PERC 2 was published. It is available to download, free of charge. This is a must read for every plumbing engineer. If you are not familiar with PERC, it stands for Plumbing Efficiency Research Coalition. Their research involves solid waste transport in drainage systems using high-efficient water closets.
If you haven’t read PERC 1, I would suggest you first download and read PERC 1 before you review PERC 2, which really is a continuation of the testing that was done in the original.