Originally posted by SamR link=1205469057/0#0 date=1205469056
When water is flowing through both the group and the OPV, the pressure will drop by around 1 bar below the no flow condition. This will give you the desired 9 bar in the coffee puck.
If you measure the pressure at 11 bar or higher at the grouphead, then you might want to adjust the OPV downward. On newer Silvias, this is a relatively simple adjustment. Older OPVs are not adjustable, so some trickery (along with a collection of copper washers of varying thickness) is required.
Jim

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