Piped water, especially from industrial cooling installations, often brings a temperature increase which improves weed growth, providing a steady summer-temperature environment which is considerably less affected by the onset of cold weather. Here, fish will often feed locally when hostile water and temperature conditions elsewhere have put them off.
In one or two highly localized areas such inflows support introduced fish such as the grass carp, or unusual examples of aquaria species introduced accidentally, including cichlids or American catfish.
You probably know of a factory inflow in your locality with special significance for anglers. The local pea or bean cannery effectively fattens up the roach of the neighbourhood on a diet of peas and beans they would not usually accept, and good quality fish are often taken in the vicinity of the inflow. The jam factory releasing sugary waste, the milk bottling yard, and the local slaughterhouse are all examples of inflow areas where fish that have become accustomed to rich rations can be caught on unusual baits matching local conditions.
Whether the swim you approach offers all the classic advantages of the point, or is simply a small culvert or drain, your assessment of its contents and choice of bait must be made carefully. Each situation will differ marginally from the previous one: the same swim will vary a great deal according to water and weather conditions. You can only search out the evidence, and use judgement acquired with experience, to select the best method, tackle, and bait options.