I'm surprised these aren't standard. Most American gravity-tank-flush toilets use the same flush valve, and most of the remainder are the tray-tip kind that doe

I'm surprised these aren't standard. Most American gravity-tank-flush toilets use the same flush valve, and most of the remainder are the tray-tip kind that doesn't really have a flush valve in the traditional sense. There are exceptions and oddities, but it's really nice having singles. Also does mean you can buy just the single part you need. I have no idea how we of all places managed to get this right. Also I do wonder if a scale preventer injector (they go online like a water filter) would be more or less expensive than the toilet parts?