I live in a downstairs apartment of a two story building. the floor plans for upstairs and down are identical. April 20th my upstairs neighbor had a new water heater put in and within a week or so after that their pipes leading to the toilet began to whine very very loud when the toilet is flushed. So loud in fact it wakes me up in the middle of the night when they have to do their thing. I know its the pipes from the toilet because the whine eminating from behind my walls. I do not believe the problem is with the toilet itself. If anyone has any advice to help resolve my situation I would greatly appreciate it. I could use the sleep.