Its things like stairs and suites that I find take the water - more because of the dumping issue to protect from overheating.
I did a 3 bed, 2 bathroom, h/s/l, lounge and dining room on Tuesday and used about 160 I would say.
Again it was the stairs that took a lot but also every room had that horrible black around the skirting that needed handtooling.
Did a lounge/dining on Monday and that took about 30/40.
You get used to judging whats what and loading up for just that. I have 400 for the just in case jobs.