The 9 bar reading on your brew pressure gage is due to the thermal expansion of water within the complete brew circuit from the check valve on the discharge side of the pump to the brew valve within the E-61 grouphead.

Brew pressure gage readings at any time OTHER THAN while actually brewing or flushing are without merit.

Chris' Coffee (and possibly others) have just the right adaptor for your faucet's cold line together with a nicely sized pressure regulator, etc., etc.