Brew Pressure is Too High/Low
If you think the brew pressure in your Quick Mill Arnos is too high or too low, you can test by inserting the backflush disc into the portafilter, locking it in, and running the pump.
Coffee has too many variables to determine if the pressure issue is strictly caused by your machine and the backflush disk gives us a control model to use while testing. With the backflush disk in, the gauge should rise to 9 bars in 9-11 seconds. If it doesn’t, you may need to open the machine to adjust the OPV to the correct pressure.
Note: Although the machine featured in the video below is the Profitec Pro 700, the Arnos is similar enough that the process described will work for both machines.
How To Adjust Brew Pressure