Probably a moronic question really but can you do this without sending the machine up the wall? i.e. can you close off one tube or only connect one? I am dithering between the Ardo Calypso and the Ameda Lactaline. I already have a Medela Swing but never being able to get the tube totally clean has made me think of getting another one. I tend to pump whilst BF so would generally only need one pump but thinking would be handy to have a double one in case I ever get organised and do pump at some other time other than when feeding. Thanks!