Sir, one or both of my Delta knobs in the bathtub is leaking. I have pulled the caps off, taken out the long screws and I am now confused. Coming out of the wall are 2 silver pieces with plastic pieces coming out of them that supposedly come out in order for me to get to the washers. I have tried to use a 15/16 socket to try and turn these metal pieces but it is not big enough to go around. What can I do? These Delta knobs have been in the bathroom I believe since 1986 when the townhouse was built. Thanks.