Grohe Blue Activated Carbon Filter 40547GROHE Blue activated carbon filter purity and taste for regions with soft water Refreshing and great tasting water guaranteed straight from the tap. That's the beauty of GROHE Blue and the GROHE Blue activated carbon filter, which is designed for areas where the water hardness is below 9 dKH. The smart three phase filter, which has a capacity up to 3000 litres, removes all unwanted materials and impurities. First coarse particles as dirt are filtered