I'm using Jobo Expert drums to develop sheet film and wonder if I use water as stop bath, how much water should I use if say I have used 400ml of developer, and then for how long?
I use a Jobo 3010 Expert Drum with a Jobo machine and I use 500ml of Stop Bath in mine. Remember we are talking about the cheapest chemical used in photography other than PhotoFlo.
A 500ml water rinse will be fine. That's what I use with sheets in Expert drums regardless of developer quantity, even when I've used a full liter of developer. Anywhere from 30-60 seconds is OK; I time 60 seconds from when the water is first poured in until tipping the lift to drain.
There's no need for an acid stop, although it won't hurt anything to use one.