I've been developing an interactive map of the Manchester system for a while, it's a schematic diagram designed to show the relative positions of the sewers, overflows and rivers rather than actual physical locations.
It's not finished which has put me off posting it by itself previously, but then it never will be so not time like the present!
White circles can be clicked on (desktop only), the whole thing can be dragged and the navigation buttons allow zooming and the different stages of sewer building to be toggled.
http://substormflow.com/location/manchester/map/