When my upstairs tub/shower combo is on water leaks downstairs to the ceiling garage. I've tested the bath and nothing leaks but when just the shower is on it leaks. I know the diverter doesn't work properly because when I press the shower knob in, water comes out the shower head and the faucet at the same time. Would a bad diverter valve caused the leak in the garage. I've tested toilets, sinks, upstairs air conditioner. I am a women who is not mechanically inclined and can't afford a plumber. I'm determine to fix this myself. I can get someone to repair the garage ceiling but need help with the plumbing.
Need Help!

Before we can help we have to know what you have. A one handle valve with a spout diverter? A three knob valve with the diverter in the middle? Can you remove the face plate on the valve and tell me the source of the leak? Back to you, Tom