I stopped using those pumps altogether. I went to the local feed supply store and bought several 60cc plastic syringes. Went to the local pet shop and bought some 1/4" aquarium air hose and threaded a length of hose into the hardener and resin jugs through a hole I bored in the top of each cap. I plug the syringes into the end of the hose and draw out the resin or hardener I need. Takes a bit longer to draw out larger quantities but it totally eliminates mixing errors due to those pumps. Use a clothspin or spring paper clip to pinch the hose to keep it charged. You can mix as much or as little as you like that way.