La Pavoni Pro Millenium -- when I dump the false pressure (and any accumulated water) through the steam wand into a cup, the water is tinted yellow and has a metallic smell. However, if I flush the brew head into a cup, I don't notice either the yellow tint nor the smell? Time to descale? But how to clean the steam wand? I ask because someone here said not to run the descaler through either the steam wand or the brew head.