My method of flushing the steam boiler is to open the water tap after I am done steaming and before I turn off the steam boiler. I run the steam/water until it stops (~210F), wait for the auto fill and turns off the boiler, leaving the brew boiler on.
I measured it and there's about 22oz going out.
I thought about this thread today when I did it, and it occurred to me that maybe I DON'T like that there is 22oz of cold water going into the hot boiler all at once. I don't like the rapid change in temperature on that metal and connectors. Maybe it would be better to do this by the end of the day or by the last cup. Turn the machine OFF, then open the steam boiler water tap to let those 22oz out, but no auto fill until the next morning when I turn it ON. Comments??