More than likely you have a leaking boiler valve. This is essentially a spring-loaded part that is supposed to keep water from leaving the boiler unless there is sufficient pump pressure to overcome the force of the spring. The leak can be due to a weakened spring that no longer provides adequate force, an obstruction in between the valve surface and the "seat" against which it is supposed to seal, or a defect in the valve surface.

I have a Sirena and my problem was that there was corrosion on the surface against which the valve seats. Access to these parts is via the brew head area, and although you can access it from the underside, it's pretty difficult to visually inspect the valve seat without significant disassembly from the top down. I managed to clean up the valve seat area, which has pretty much eliminated dripping from the boiler (but not from residual water still draining down through the grounds in the portafilter after a shot of espresso has been pulled).

To get an idea of what you're getting yourself in to beforehand, do a search for the terms "Starbucks Sirena", "Saeco Sirena Boiler Ball Valve", and "Saeco Sirena Boiler Valve Spring." (The Sirena was made for Starbucks by Saeco.) Look for an exploded view diagram of the disassembled Sirena. A replacement spring and ball valve are relatively inexpensive (~$5 US), but if the valve seat can't be cleaned up sufficiently, you need to replace the lower boiler (~$60 US).

Good Luck!

Rob More than likely you have a leaking boiler valve. This is essentially a spring-loaded part that is supposed to keep water from leaving the boiler unless there is sufficient pump pressure to overcome the force of the spring. The leak can be due to a weakened spring that no longer provides adequate force, an obstruction in between the valve surface and the "seat" against which it is supposed to seal, or a defect in the valve surface. I have a Sirena and my problem was that there was corrosion on the surface against which the valve seats. Access to these parts is via the brew head area, and although you can access it from the underside, it's pretty difficult to visually inspect the valve seat without significant disassembly from the top down. I managed to clean up the valve seat area, which has pretty much eliminated dripping from the boiler (but not from residual water still draining down through the grounds in the portafilter after a shot of espresso has been pulled). To get an idea of what you're getting yourself in to beforehand, do a search for the terms "Starbucks Sirena", "Saeco Sirena Boiler Ball Valve", and "Saeco Sirena Boiler Valve Spring." (The Sirena was made for Starbucks by Saeco.) Look for an exploded view diagram of the disassembled Sirena. A replacement spring and ball valve are relatively inexpensive (~$5 US), but if the valve seat can't be cleaned up sufficiently, you need to replace the lower boiler (~$60 US). Good Luck! Rob