I live in an 80-unit apartment building. It's a pretty old building. Ever since I moved into my apartment, the tenant that lives in the apartment below mine has been tampering with the hot water every time I take a shower, no matter what time of day it is. She even admitted to this in a note she slipped under my door because she doesn't like me. Of note, the unit above me is vacant. I live on the 4th floor, and the psycho tenant is in the 3rd floor unit directly below mine. When I shower, the water will initially come out very hot then suddenly the water pressure decreases and I can feel the hot water getting colder. After some time of being in the shower, then the water will get back hot again with increased pressure. The same thing happens when I use the bathroom and kitchen sinks. I've reported this to my landlord numerous times but they don't care or believe what I say. They told me that no one can control the water in the building but I know that's BS. The tenant in the unit below me is definitely doing something to tamper with hot water, I just don't know exactly what that is. One of the owners of the building confirmed that the units above and below mine get hot water. Like, really hot. However, my hot water isn't maintaining its heat like it should. I've noticed that whenever any maintenence people are in my unit, the hot water suddenly gets very hot with appropriate water pressure. But as soon as they leave, the hot water temperature and pressure goes down. This is no coincidence. My main question is: what exactly can a tenant do to tamper with hot water in a building? Are there any dials, levers or faucets that they can manipulate? Please, I'm seeking professional, well-informed knowledge only. Do not respond if you don't know what you're talking about.