I had a plumber rough in a new vanity and shower for me. He crossed the lines somewhere so now the hot is on the right for the sink which really is no big deal. I am concerned that the hot and cold for the shower valve is also backwards...how can I tell before I put up board and tile? I have tried to feel temperature differences even tapping on pipes but nothing has let me know...also this guy is licensed and was a family friend don't want him back in my house