The basic mechanics of a toilet are, in theory, really quite simple. The tank hold water which is released by raising the flapper. This sends the tank of water into the toilet bowl and washes the contents through the trap and into the drain. So much for theory. In the real world, there are engineering variables that allow some toilets to work better than others and there are components that can get out of adjustment or fail. As Jadnashua and Plumber 1 have noted some of these. With the advent of the low water volume mandates, the difference in brands has become more and more of a factor. In the "good old days" the main difficulties were the internal parts that failed or got out of adjustment and unless the toilet became clogged, the volume of water would assure pretty good flushing from most any of them. Today, the engineering of the toilet has become paramount. Most of the problems with newer toilets seem to be with the low cost builder models and not so much with brands that have spend time and money in designing toilets that will function well with low volumes. Of course, these cost more money. I have never been in the UK, so can not speculate about the problems there, but I find it hard to believe that the problem requiring multilpe flushes is normal.
