The other day, my shower decided to start running on its own, the faucet was off, but water was coming out. I played with it and nothing changed so I called my landlord. While on the phone with him the water stopped. So I told him not to worry about. 1 hour later the water started again. I tried playing with it and it wouldn't stop, so while we waited for a plumber we decided to collect the water because eventually we were going to run out.
Turns out the plumber couldn't come until the next day. Once I heard this I decided to play with it some more and in doing so I discovered a brilliant way of stopping the water. I turned the faucet all the way to hot (while still in the off position) and then shut off the hot water heater. This seemed to work, the water stopped flowing. I then went the bathroom and when I went to wash my hands in the bathroom sink and turn on the faucet guess where the water came out of...you got it the shower faucet and not the sink faucet. At this point I kind of laughed and said ok, well the pipes must be connected because they're in the same room. No biggie.
Later that day I went to make some food, I tried washing the vegetables in the kitchen sink, but no water came out. That's right, it was coming out of the shower faucet! So turns out all my water sources are connected and when the plug in the shower faucet breaks, it prevents water pressure from building strong enough to force the water elsewhere. The plumber eventually came and solved the problem and now my kitchen water pressure is better than ever, but my shower's pressure is worse than ever.