Excellent teacher, me!!
From the very beginning 500ml has been the norm, 350ml for the hot water sterilization and on some machines 750ml for the cold water rinse, there is also (500ml) water used during priming.
As a total of the water consumed Ariel should be looking at the output of the RO, how much is supplied to the 'loop' and how much of the water is being rejected, not as simple as calculating the quantity of machines and multiplying by 500ml for the total water consumption.
