My shower is leaking when I turn on the shower. I have a delta shower and when I turn on the water as if I'm going to take a bath and then adjust the temp... the water will leak... then when I turn the shower on, the leak will go away... I'm guessing the o-ring or o-rings need to be replaced, but I cannot get the brass slive off to get at the o-rings.. what do I need to do to get at these o-rings.