Why can I hear water running in shower drain when I'm not running water anywhere in my flat? I'm in a listed building that's been converted into 4 flats and, to be honest, I can hear water running in more than one place. I previously posted about hearing it under the kitchen sink but that stopped after I installed an anti syphon trap. I can hear it running through pipes boxed in next to the sink, which I'm absolutely sure are shared with the upstairs flat. The sound of running water in the en-suite shower is just as annoying because I can hear it when I'm trying to sleep and it's extremely distracting. Is this another shared waste plumbing effect? I can't attach a video to let you hear the sound.

