Leak in Ensuite Roof Ceiling Below SVP Pipe in Loft Drainage and wastage systems and plumbing help, advice and answers

[Dough66]

Afternoon all, I noticed a mouldy patch within my ensuite ceiling, and assumed the tiles roof above was leaking. However after going into the loft space directly above the ensuite I noticed the large SVP pipe running horizontally across the inside of the attic entering the corner of the loft where the leak is below. This pipe then turns by 90 degrees and goes out thought the roof. I notice however that as it connects to the vent inside the attic it is just propped in place as the pipe goes from say 150mm to 100mm and does connect properly and the previous occupant of the house has jammed the pipe in place without connecting it to the base of the vent due to the varying diameters. I placed a tray under the elbow thinking that the leak was via the poor connection. I have looked at the vent cover from outside the house and it's look ok. I attach some images and would be grateful for any advice on why the tray I have installed is collecting water. Is it due to the SVP being too horizontal, and not draing the water away that has got into the pipe. Also there doesn't appear to be a hole in the bend of the pope either. Advise would be appreciated. Thanks

[thedoctor]

There should be no water in this SVP, it's purely to take bad gasses out through the roof so couple of condensing possibilities here.

Its cold in the loft (or should be) and the pipe wall probably chilly. Any warm air coming through the ceiling might be condensing on the outside of the pipe and dripping off at its lowest point.

The warm gas inside the pipe may be condensing on the inside of the cold pipe wall and running down the inside of the pipe to it's lowest point where it is getting out of a faulty joint.

Or the rain could be blowing up into the roof vent getting into the pipe and collecting in the bend.

Either way it would be a whole lot better if the SVP could be tilted up,fixed to the underside of the rafters and the vent taken much higher up the roof. The gas inside the SVP is warm, it wants to rise which means it willgo to the highest point of the pipe which, judging from the photos, is actually nearer the toilet than the roof.