My varistream was only set to 4 and I Use a tap
I find that 4 is the max I can set mine at.
I love to work with 5 or even 6, but I don't work quicker, I just waste water.
Lee runs a very successful business, so if his guys use 600 litres each a day, great, I could also use that amount, but I wouldn't be doing much more than working with 4. I can only work with No4, anything higher for me is a waste. The younger guys should achieve more though.
In the early days we used 1/2" hose, Shurflo pumps running flat out with 3mm jets in the Vikan brushes with Unger Teleplus poles. 450 litres finished before 3 o'clock.
We upgraded to minibore hose, 2mm jets, Varistreams and Carbon fibre poles with Bentley brushes and did more work a day using less water as we had enough to work till 5.
However, when I use our backpack, I notice how much time I waste rinsing with a very low flow rate.
In the old days we didn't have a fast producing R/O, now we have a 4040. Its better to use too much water and waste a bit than wasting time with a too low flow rate.