see, heres the thing, flushing with only 2 liters in a 5 liter container isnt flushing, its just heavy watering, i dont think you'll get any benefit from it, that sucks ya cant get more water but i have an idea for you, since u use the metric system instead of gallons im assuming your not from the us? im not sure what stores you have where you live but look into a pur water filter ($30 here) or something like that.(they even have a pitcher that the lid has a filter in it now thats like $15 here)