This photo was taken from within a cracked sewer pipe.  The water seen entering from the top of the pipe is known as infiltration and inflow (I/I).  Infiltration occurs when water enters the sewers through defects such as leaky pipe joints, and cracked or corroded pipes and manholes.  Inflow occurs through manhole covers, cleanout pipes or illegally connected drains or roof downspouts.  Excessive I/I is highly undesirable for the sewer system because it taxes the carrying capacity of the system.   [Close window]