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Cooling flush
Running water from the group on an HX machine (with no portafilter engaged) to purge steam-heated brew-line water before pulling a shot.
Category: Boilers & Heating
A short burst of water pulled through the group on an HX (heat-exchanger) machine that has been sitting idle, to clear over-heated water from the thermosiphon loop before pulling a shot.
Why it matters — On HX machines, water in the brew path heats up while the machine sits — sometimes well above the target brew temperature. Without a cooling flush, the first shot pulls too hot, often producing sour, burnt-tasting espresso.
Good to know
- Typical flush is 2–6 seconds, until the flow runs smoothly and steam stops sputtering.
- A built-in shot thermometer (Eric's Thermometer, Scace) takes the guesswork out of timing the flush.