I put don't know, I pay for it. I used to know, and I keep an eye on our averages compared to previous years for the same period, but at the end of the day, we try to be as consciencious as possible, and our water usage is what it is.
I have looked at, and have determined that the water saving features (grey water recycling, rain water to toilets etc systems) are not economic, so until they are properly subsidised, I can't afford to put them in.