Sanitary Sewer Operations: Blockage Removal

By NASSCO member Stephen Tilson, Collection Systems Operations Consultant, Tilson Associates | June 2010 Vol. 65 No. 6

Debris removed from the blockage should be examined and evaluated to determine the possible cause. Blockage removal commonly calls for “two up/two down” cleaning once the blockage has been removed. This refers to the number of pipe sections above and below the stoppage point and any intersecting sewer lines that may be impacted. CCTV inspection should be a primary follow up tool to assess cause/cure elements of mechanical problems, root intrusion, or fats, oils & grease (FOG) that can be controlled.

In review of types of blockages, weeping blockages are typically found during routine maintenance or from customer odor complaints from bio-mass accumulation in the system. It is not unusual for a long term weeping blockage to have over two pipe sections holding materials that will need cleaning. This usually requires a brief investigation of manholes upstream from the clear manhole to assess the pipe sections that will need cleaning once the blockage is removed.

Blockages are a very visible failure of the system and should be managed in a professional and expeditious manner to maintain public confidence.

Stephen Tilson is a nationally known collection systems operations consultant, providing successful SSO reduction programs and equipment operation education. He can be reached by email at