When you start up, you will use a lot of water until you get to know what you're doing.
To give you an idea, 2 men, 20-25 houses, uses about 4-500l.
There is no exact science to what you will need, as some like high flow, and rinse 2-3 times, some have a low flow and rinse once, so it's all theory until you get out there and try.
Our 4040 boosted system does around 150l per hour, give or take. This varies with the temperature.