An apparatus for continuously controlling fluid flow in a sewer conduit, comprising: a) moisture sensors detecting levels of fluid in this conduit; b) an inflatable bladder, mounted in the sewer conduit for releasably sealing in fluid tight fashion a section of this conduit; a compressed air source for inflating the bladder; and a control box including a CPU sensitive to the moisture sensor(s) and actuating the air compressor responsively to conduit fluid level conditions reaching beyond a preset threshold value. The performance of the apparatus is independent of the speed of fluid flow in the sewer conduit.