Why isn't my new toilet flushing system working as well as the old one?
I replaced the systems in all 3 toilets of my current house when I moved in, and I have had endless minor problems with them since. "They don't make 'em like they used to".  I get double flushes about have the time and keep tweaking the flapper settings.  I am about to start replacing them again with high-end adjustable flush systems.  Anyway, the height of the refill tube, and the height of the water is key to a good flush. Regardless of how much water you use per flush, you want the water to be as high as possible when you flush.  Some systems have shorter refill tubes than others.  And you want the water to come within about an inch of the top of the tube, but not higher than the water line from the valve, or it will siphon water continually.