BTO Bedroom Leaking at Trunking: Drain Pinched by a Shelf

Escaping water at the trunking in a bedroom of a flat that drained without difficulty for a period. A shelf was fitted along the same wall at some point beforehand. Attempts at clearing the line have found nothing at all in it.

A clearing attempt that finds no material is a result worth taking seriously rather than repeating. Where nothing comes out and water still backs up, the pipe's capacity has been reduced without anything filling it. That points outward, to whatever is bearing on the trunking, and the check is physical rather than technical: follow the run and look for anything fixed, leaning or mounted against it.

Trunking is a light plastic channel and the pipe inside it is thin-walled. Anything fixed tightly against the trunking transfers that pressure to the pipe, which flattens rather than resists. A pipe reduced to a fraction of its section carries a fraction of the water, so it backs up under ordinary condensate production while remaining completely free of any deposit at all.

The pressure is relieved so the trunking and the pipe recover their shape, which frequently needs nothing more than repositioning a single fixing. The general point is worth carrying forward: where clearing finds nothing, stop clearing. A drain that will not flow and holds no material has been restricted from outside, and continuing to rod it wastes time and can damage the pipe further.