Everybody does it differently. I don't know how much water I would use on such a job, I work by results. If it "feels" right, I guess I'm using enough water - making sure the glass and frames are thoroughly scrubbed and enough water runs down while I'm rinsing so I feel confident the job's done properly. I fill my 400l tank every day, but lots of times I only use half to two thirds of it. I also judge by how fast the water comes out of the jets - if it "bounces" off the glass there's too much flow, if I have to sweep back and forward several times to rinse properly, there's not enough.
Some people can do a whole days work on 150l, others need 500. The only criterion is the result - if the glass/frames etc are clean and without spotting, then you're using enough - and maybe too much - water. If they're not clean, you probably need to use more (or look to your technique :

)
Cheers,
Ian