Abstract: A sewer blockage alarm for a sewer line having a pressure sensor mounted at the top of a clean out branch section of the sewer line which is connected to a large diameter pressure multiplying pressure bell via a length of flexible to be dangled at the entrance of the branch section. An audible and a visual indicator are activated by slight pressure rises caused by water level rising to the tip of sewer line to provide an early warning of an incipient blockage condition.