I recommend you use a food injector type syringe. Gauge is a bit bigger and the tip is not sharp (mine has no needle point to it). Also has a small hole on the side near the tip end where liquid can come out if you put the syringe to the bottom of the carto. I have poked myself a few time by accident with it but never punctured the skin. I have 2 1 for cleaning the carto 1 for filling. To clean just insert the injector to the bottom for the carto till it hits the bottom then press. Water will come out the side hole of the syringe into the carto. I do this with 200+ degree water repeat 3 or 4 times and your carto is almost as good as new to. Just remember to submerge the carto in water or it may get messy.
