I've always heard that you need to flush HX machines, because the water is initially boiling hot. By running the water through the head, it pulls cooler water from the reservoir which gets heated to the proper temperature.

I bought an E61 thermometer and have been flushing like I've been told for the past year or so, until recently.

I noticed that if I don't flush, the temperature at the thermometer never goes above 209, and most of the shot hovers around 206. The temp at the basket is supposed to be a few degrees below that, even.

My shots are delicious as ever, and I don't have to fill the reservoir nearly as often. I also don't have to empty the drip tray nearly as often.

Is flushing really necessary? My house is warmer in the summer, but only by a few degrees. It's possible that could make a difference, so I'll keep an eye on it once the warmer months roll around.