I wash my film by filling the tank (a Patterson daylight tank for medium format, and the Doran tank with the top off after tray developing for 4x5 film) twelve times rather slowly, swishing the water vigorously but not violently, and pouring it out. I have never had a problem with the film I've used this technique with and I've been using this method for over six years. It only takes a bit over ten minutes and saves a lot of water from the tap I believe.