Trenchless Technology Center
Louisiana Tech University

Water Environment Research Foundation
http://www.werf.org
 
SEWER LATERAL INSPECTION

Sewer laterals are being inspected to identify :
  • Existence of leaks, e.g. cracks, joints, etc. that are either actively leaking at the time of inspection or with stains that indicate leaking at other times, and sometimes to determine severity of these leaks (i.e. to quantify them for certain rainfall or groundwater conditions)
  • Various connections to the pipe such as area drains, etc. that are likely sources of inflow
  • Structural defects such as cracks or holes in pipes that have led or could lead to the collapse of pipes
  • Any defects at connections in the pipes that are often a weak link
  • Existence of roots in pipes and the extent of their growth in them
  • Corrosion and mineral buildup that have reduced the hydraulic capacity of pipes in time
  • Bends in the pipe (location and degree)
  • Any existing sags or misaligned joints that can promote buildup of material in the pipes
  • Any change in pipe material along the length of lateral as well as change in pipe diameter
The lateral inspection methods shown below are included in our database. Click on the link to see details.
METHODS:
Smoke Testing
Dyed Water Testing
Lateral CCTV Inspection
  Push-Type Lateral CCTV
  Self-Propelled Lateral CCTV
Mainline CCTV
Pressure Testing
  Air Pressure Test
  Water Exfiltration Test
Electro Scanning
Smoke Testing


Smoke testing is performed by placing smoke bombs in an isolated section of the sewer system (plugs or sand bags are typically used to block the flow). The generated smoke is passed through the pipes and, if any cracks, open joints or similar defect exist in the pipes, the smoke eventually appears above the ground thus indicating infiltration/inflow sources in the system. The application of this method is hindered by sags, traps, mineral build-up, and/or high water level in the lateral (the method is therefore preferably performed in dry season). Smoke testing is believed to detect only a portion of all leaks in laterals (e.g., 1/3) but is quick and inexpensive, and is typically used only as a screening method for inspecting larger areas.

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