It's got to be an overflow from a WC or tank on the floor above how many flats on that floor?
The camera option will not show where it is and will be expensive!
I do have to say that in your situation I would be inclined to block it and see what happens next!
I suggest you make a log of times and days it flows and see if that corresponds with any particular flat being occupied or perhaps unoccupied.
Can you measure the flow rate in litres per minute?
Tony
Yes but if you can see it and set up a similar looking flow from a tap then measure it as it gives me an idea of what could cause it.
Also how long it flows for.
The log of WHEN it flows will perhaps be the most useful. I don't see why being a tenant makes any difference unless it is just that you are not wanting to go to the trouble!
Just because YOU don't have an unvented cylinder does not mean that those above you don't! I am not quite sure the relevance of that picture. We would need pictures of each of the cylinders! Their location relative to the outlet would also be a very big clue too!
Tony
Does the flats has it own cold water tanks?
What behind that wall in airing cupboard?
Maybe plumber isn't doing his job? I would find it easily.
Dan.
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