I am renovating an apartment on the top floor of a four story house. I installed a single handle shower mixer and a separate tub (which has a two handle and spout layout). I turned on the water to the apartment and everything seemed fine, but now there is warm water in the cold line in all of the apartments. Does this mean that the shower body is bad? did I connect it wrong? is there a backflow valve that I missed or something? Or could this be something worse and there are crossed hot and cold lines somewhere? What do I do to fix this-help!!