I am not fishing for the job - far from it! - just giving you some guiders
The water supply - is it tucked out of the way, not over looked?
We cleaned 18000SQM of Tarmac, six of us in six days.
We have cleaned slab 4000SQM in a couple of days, with chewing gum removal.
I wouldn't worry too much about the down time on going to fill up, it just isn't worth trying to find those amounts, you will spend more time setting up and breaking down.
A 4 inch riser (illegal) will fill a 1000l tank in 1 minute, a 1 inch riser will take about 20 - 25 minutes, just allow for filling/down time
Rob