leave some room btw the bottom of the container and the drip valve. u do not want all the residue from the kalk which settles at the bottom of ur container to clog up the valve. remember not to seal the container with a cover, coz if u do, there will be no pressure in the container to push the water thru the drip valve. juz leave the container uncovered. if u wanna use a cover, juz drill a hole in the centre of the cover to facilitate the atm. pressure acting on the kalk solution. so that it will push the kalk down.
juz me 2 cents.