There are some drains that are known of but remained out of reach, only snippets of information provide suggestions of what maybe found. 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.
The drain starts as a stoopy 4ft brick pipe before turning into RCP and opening out into a circular chamber. The RCP continues through and changes to what must have been the original culvert. This alternates between 4ft brick and stone before shrinking into a bare rock tunnel, I didn't venture too far.
Up in the chamber are a short series of steps that curve upto the overflow pipe. The railings had been flattened by the force of previous overflows and now lie as a twisted jumble of metal tubes across the pipe. A bricked off section has a small sewer flowing at the bottom which comes from a concrete box that shares the overflow pipe and carries the normal level flow.
The overflow pipe continues up for around 50m before meeting a spiral staircase, the sewer travels down one side in a cast iron drop pipe.
The stairs go up some way before emerging into a large circular chamber.
From the height of the jamrags it looks like the staircase cannot handle the overflow from the main sewer in full flood. A storage area of sorts around the side of the chamber provides extra capacity and appears to drain via a pit.
A connecting pipe leads up to the CSO chamber itself. On the other side of the processor the sewer exits via a small slot and enters the top of the drop shaft.
Big shouts to TheVicar and Nckt, great to finally see this drain.