Intermittent Leak

[getonwithit]

I rent out my flat which is on the second floor of a Victorian building , there are 8 flats in the building and most are rented only one owner lives there in the flat above me , there are 2 flats on each floor all the flats at the rear of the building including mine flat 2, have bathrooms at the front of our flats and all flats on front of building have flats at rear so we all sort of share service pipes and our bathrooms are all sort of top of each other ,
6 weeks ago water started dripping through my ceiling at about 10am my tenant went upstairs to inform flat above who called his plumber ( who had been there the day before repairing toilet ) he checked no leaks I assumed when he detached pipe water might have gushed on floor for a while ,
2 weeks on no leaks then started again same time called plumber again couldn't find anything ,
Now every day except weekends water pours through between 8 and 10 am have had 6 different plumbers out , we have accessed all flats and ran showers and sinks and flushed toilets ! I thought it could be something to do with emersion heater on in one of flats and pressure pushing water out as you can imagine it's very frustrating for us all
Lease holders not interested as it's an internal matter !
Any help much appreciated
Thanks

[KARL]

You describe what some people would describe as a type of living nightmare - these things can be extremely frustrating but it is very nice to read that there seems to be no acrimony between the different people affected.

I think in the end I would be inclined to work back from where the symptoms appear to emanate from (your ceiling or further back if identifiable). You don't mention the materials involved in the floor/ceiling areas or whether there is a "utilities space" through which all pipework passes - these questions are important because it looks like you are going to have to work your way back from your ceiling upward (possibly sideways too at times) until you reach the location on the pipes where the leak originates.

The fact that this seems to occur regularly for a two hour period each working day does suggest it is a sewer/drain pipe that is at fault (a joint ?) and, moreover, that logging the habits of people above you might provide a clue - does the water have any waste characteristics ? If it were a water supply/distribution pipe then the supply pressure would have to fluctuate substantially to produce an intermittent leak (in my view not likely) - a way to check that would be to install a pressure gauge in each suspect flat and monitor them at hourly intervals. Finally, what could be the culprit is some sort of overflow or relief pipe or a joint on it - these should be flushed to see what happens and ideally visually inspected along their full length. It is worth remembering that there can be a time lag between the water escaping and eventually showing where it becomes evident.

A heating circuit leak is also a possibility and the best way to check that is a bit complex but shouldn't be beyond any competent plumber - I regard this as the least likely source, but I wouldn't dismiss it entirely.