I have been using the same ss tanks for forty-two years usually doing two 120 rolls in the 1 liter tanks and as mentioned tilt the tank when filling and emptying. It usually takes about 8 - 12 seconds. I never worry about it since developing in ID11 1:1 @ 68F takes fourteen minutes it is a very small percentage and I have not noticed any adverse effects such as over development or too much contrast on my negatives.