I'm seriously at the end of my tether with this. I've been experiencing vibration of my floor in all rooms in my small first floor flat for the past year. I think the only way to solve it is to have the water heaters checked in the adjoining flats, the one below me, the one next door and the one below next door (this would seem an unlikely source apart from often when I'm woken in the early hours of the morning, the lights are on in this property as the person is going out to work early - this is also true though of the next door neighbour). I believe all the flats have unvented water heaters and no one has gas. I've looked at the pipes on the outside of the building which I believe are for overflow from an overheating water heater, and 3 leak water. Mine does (but a plumber has told me there is only a slight fault on my water heater which he will be fixing soon, in any case I'm keeping mine switched off and only using the immersion in the mornings so that I can rule it out), but we're talking a few drops. Downstairs leaks regularly every few seconds sometimes and three times this has been the case in the early hours when the vibration is at it's worst. The other leaking pipe is from the person downstairs from my side neighbour. A plumber visited recently for a chat and initial consideration of it all and he thinks it may be worth checking all water heaters and also he mentioned something about the cold water tank....he said this would be the only reason I may get vibration across my floor from the person underneath next door....if it is coming from there. Environmental health are saying they need to witness this before acting. I cannot understand why they can't just request to run some checks with my neighbours. They may not be able to insist, but what is wrong with making a request? I've requested it of my side neighbour but he didn't answer the question and I don't want to bother him too much as he happens to be a nice neighbour (also his pipe is the only one that's not leaking, but he has mentioned that he's had a valve replacement on his water heater and wonders if it will hold sometimes). My downstairs neighbour (the one directly underneath my flat) has agreed to run checks and so far nothing is causing it but her pipe is the one that's leaking regularly when the vibration occurs in the middle of the night. Should a plumber go in and check her water heater first do you think? She would be in agreement if it were felt important. I'm reluctant to harass my neighbours when I'm not clear where its coming from, I've already asked all of them and no one else is experiencing it. Please don't suggest I'm imagining it because I'm not, I have a witness to it (sorry for the defensiveness but I've been trying to solve this for a year and have had this suggested a couple of times and it's really not helpful) Thanks for your time I would really appreciate any thoughts on what it could be. I needed this solved a long time ago I'm beyond stressed now and would move tomorrow if I could.