Recently I installed a new bathtub in my basement. Everything's working well except that the single handle Moen fixture leaks--pours--water from the shower head only when turned to warm. No leaks on only cold or hot. The shower head is about 50" or so from the handle and connected with half inch copper. Does anyone have any ideas on what the problem may be? Thanks for the help!

What's the house pressure? This can be determined by purchasing a hose bib pressure gage. Let me know. Tom