I just installed a new Kohler bath & shower faucet. The system is a single handle pressure balancing valve also new Kohler. Here’s the problem. When I turn on the water to full hot everything works fine, the water comes out the tub spout and no water comes out the showerhead. But as soon as I turn the handle back down to warm or cold, water starts coming out the showerhead and continues out the tub spout. The pressure out of the showerhead is not full pressure but about ½ flow. Does anyone have and ideas? Thanks for the help in advance.