as great an experiment that was do you really need to have your tank sparkling new? I dump, flush a few times quick, open the drain,close the drain and get out of the way for the next guy. I got stuck behind a couple that carried in 5 (five) five gallon buckets into the bath to dump into the toilet. And the line behind me wasn't too pleased either. As said, the variables involved will make a differance. I have 2 90 deg elbows before the outlet valve and a T where the valve is to drain the gray tank which really comes down to 3 90's. A flusher probably won't do much.
