I had been pondering over one such drain with along with Nckt and TheVicar for a while now. We knew this drain had an unusual setup so were eager to finally explore it.
This CSO system is Heywood's largest overflow into the River Roch consisting of 3 separate sewer overflow connections which meet before dropping into a culvert to the river.
This CSO into a small brook provides a screened overflow for the upper part of Heywood's sewers.
The chamber serves an 8ft sewer, overflow weir and the brick overflow pipe I had been looking for. Unfortunately it was thigh deep in river level water which slowly rose and fell with it's load of rubbish from previous overflow events.
The manhole shaft leads down inbetween the A & B Outfall sewers. At the bottom is a 6ft pipe that connects both trunks to allow the flow from one to enter the other when flow levels are high.
A connecting sewer gives a close up view of one of Manchester's massive trunk sewers.
I thought this might be a bit more interesting then the small pipe and CSO it turned out to be, until you go you don't know.