Stupid question time but it won't be my first - or last. I've fitted dozens of them and replaced conventional syphons with them but I'm unsure exactly how they work. Even taking one apart hasn't really helped. A syphon I understand - and how the principles of short and long flush work. I understand that a push button has a seal which is lifted to release stored water but why doesn't it close again immediately on releasing the button and furthermore, how do long and short flush differ? It's just one of many things that puzzle me.