Hello Everyone, I have a main water shut off valve that keeps spinning and would not turn off the main water supply. I have to turn it off to work on my shower. I dont know what to replace. So I would turn the main water shut off knob off (counter clockwise) but it just keeps spinning and doesnt do anything to the water. HELP!!! what do I need to replace? easiest technique please... I have attached a picture of how my valve looks like. Thanks everyone!