grey water is also produced by washing...that water isn't drinkable as it has soaps, detergents, and potentially human pathogens in it (though it can be treated, technically).

Also, you can save water in your toilet by adjusting the float so there is less water in the tank between flushes. My toilet is a low profile, high efficiency model. I think it uses 5 or 6 L but I'd have to check to be sure.

You can also save on flushes by not flushing as often. Only flush for #2 and you can save a lot of water.