Re: Tub/shower turns on by itself!
Sounds like an internal seal may have rolled out of it's groove and is twisting up as the valve is operated, it turns itself on as the seal is releasing the twist.
Google your brand/model valve and get the manufacturers instruction manual for it. From there you can look at the exploded view and rebuild the valve. Rebuilding a valve is usually a pretty easy process. Once you have the parts, turn off the water supply, take apart the valve, replace parts, reassemble, turn on water and test. Only do this if you've got the owners manual to walk you through the procedure or have experience rebuilding a shower valve.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!