hello all, installed a new shower fixture and a handheld shower on what would normally be where the tub spout would go. I also installed one of those small shut off valve that you normally put on your shower arm where I have the handheld shower. when I turn the shower on, I get water coming out of the showerhead and the handheld shower at the same time. can someone give me any advce as to what I messed up? thanks