From time to time your Bacchi may not whistle as shrill as it should. The ‘drains up’ way to address this issue is to remove the middle of the three valves in the piston, disassemble it, looking carefully for any debris and removing it, then carefully reassembling. This is a bit of a prolonged affair, and in our experience is often unnecessary.
Often all you need to do is grasp the flat on the stem of the middle valve between forefinger and thumb(clearly shown in the image below) and jiggle it no more than 30 degrees clockwise and counter clockwise in quick succession. You will feel that the stem is sprung loaded. This jiggling action is often enough to dislodge whatever it is that is muffling the whistle, and on takes a couple of minutes to do. A 2.5mm hex key is the only tool you need, removing the 3 stainless steel screws from the top go the cylinder assembly.
