The dreaded Mix it Valve, the round plastic handle control the water volume turn it counter clockwise to much it like shutting it off. The temperature control level is on the plastic stem and if not tighten down correctly it will strip. For the average user it can be a nightmare because its not user friendly, if your home is over 10 years old I suggest replacing it unless you can live with it. However parts are available even though I have replace all parts in these Mixit I still get complaint about it. New code require pressure balance valves so you dont get scalded another reason to change out these valves/.