I've had my Alex Duetto for a good 6 months now and it seems that my rotary pump is having trouble. The pump is getting louder and louder almost every time we use it. It started a few weeks ago and I figured it would pass. Could this be something easy like a trapped air bubble? Could scale be clogging the gicleur? My shots have been pulling fine, I can't tell a difference in flow. The gauge goes to 9 bar like usual. What could be wrong?

Check this out:

http://www.coffeegeek.com/forums/espres...968#461968

if you're direct plumbed, then pressure could be a problem

Too high on the pressure and it will make noise, too low or inadequate supply (like an ice maker supply line) and it will get cavitation. I suggest most most people use a 3/8 OD line (1/4 ID) minimum for a plumbed in machine. The manufacturer will also have a minimum and maximum inlet pressure for the machine. I usually split the difference. My A3 is something like 2-4 bars inlet pressure so I run it at 3. It could also be a mounting nut that has backed off from vibration and the entire thing is rattling. Could be a bad bearing in the pump, bad bearing in the motor, lots of possibilities but on a new machine it is often the inlet pressure or something loose.