In this clip, we will be applying the rubber gasket on the water tank between the tank and the ball. Put big rubber gasket on. Again, this is another place that I choose to use sealant just to give myself a little extra protection. Although your kit might come with the sealant, you can get that at the supply store and it doesn't always say to do this in the instructions but it just gives you as Bob says, a little extra protection from leakage. So try it, it really doesn't hurt.