The wiring in my apartment is soooooo terrible. The place was built in 1960, and literally nothing is grounded, which I think is causing a horrible screech. Said screech is pretty easy to gate/eq out, but it's still there, and it's still super annoying. I'm trying to record at home as much as possible for the several projects I'm working on at the moment, and not have to use someone else's space.
When I lived in Nashville, I had an apartment that was literally perfect for me in every way...except that, I suspect, it had massive current (relatively speaking) running through its old iron pipes. I actually measured it with an EMF meter and it registered at more than 100 milligauss in some spots - that's OFF the meter. This gave me a horrendous amount of guitar buzzing in every room, to the point that recording was impossible. There was no way I was going to convince the apartment to fuck with the water system and install dielectric unions or whatever, so...I moved.
Buhhhhh. That's very likely the situation here as well.