Do this over a paper towel in case you make a mess and be sure to have your new carto unpacked and ready to go. Use a vinyl glove or just a piece of plastic bag to cover your finger. Pull the carto out slowly until you can place your gloved finger tightly over the top hole of the tank. Now tilt the tank so that the covered hole is on the bottom and pull the carto out from the top, leaving the juice in the bottom. Now insert the new carto from the top until it almost contacts the liquid, then tilt the tank back around. Push the carto up the whole way and you've at least saved the juice in the tank.