TMY-2, Jobo 3010 tank, four washes
I just calibrated my washing method. I tested with Photographers' Formulary Residual Hypo Test (cat. no. 03-0150). The test method is to wash your film however you want to, then soak a piece of clear film (that's completed your process of course) in the Residual Hypo Test solution for three minutes. The less stain in the test sample after three minutes, the better the wash.
My process: 5x4 TMY-2, Jobo CPP-2, Jobo 3010 tank, 30 rpm, 20C. Ten sheets at a time in one liter of XTOL 1:3, dilute Kodak Indicator Stop (because I have a ton of it laying around), Kodak Rapid Fixer (no hardener), then washing:
Four washes in the 3010 tank on the Jobo at 30 rpm reversing every 2+ revolutions like normal. Washes of 500ml distilled water, for 1, 1, 2, and 4 minutes. NO HYPO CLEAR used. Just those four washes.
For testing in my last film run I ran an unexposed sheet. I cut a corner off this processed sheet for the Residual Hypo Test.
Test results: No stain detected (best result possible). I placed the cut corner on top of the rest of the sheet and still couldn't detect any stain. Even when looking at it on a light table.
My conclusion is that the "Ilford wash method" works very well indeed for my workflow. Total wash water for 10 sheets of 5x4 film is just two liters of (distilled) water, or 200ml per 5x4 sheet. Pretty efficient I think.
My secondary conclusion is that every workflow is different, and the only way to really know if you are washing your film (or paper) sufficiently is to test your process.