My house has two bathrooms - the master bath is the usual toilet, sink and shower (no tub). The main bathroom has a bathtub with shower. I’m the only occupant of the house. The main bathroom is used frequently (toilet and sink) but it has been over a year since the tub/shower has been used (the grandkids grew up and don’t visit as much). I have discovered that when I turn on the tub faucet the cold water works fine, but when I turn the knob to the hot water, the water decreases to a fast trickle and doesn’t get hot. Does anyone have an idea as to what could cause this? And what would need to be done to fix it? It worked fine before (when the tub and shower were used frequently).