I have a stand-up shower in my basement that was put in about 3-4 years ago. I went to use it for the first time yesterday and the water only trickles out when turned to hot (works fine on cold). It is a single knob Moen system with no faucet, only a shower head. All other outlets in the house work fine, even the sink that is right next to the shower. Please Help.

Thanks, Michael