15LPM would be a starting point on industrial work, in my opinion. Sole operator
211LPM would be a safe bet to clean most things. Sole operator.
If you want a twin operator unit then you need to be looking at a minimum 30LPM and that may be cutting it fine.
I have 40 odd and 35 LPM, both twin operators, the 35 is just too close for comfort sometimes but it makes up for it with user capability
Rob