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
Electro Scanning


Electro scanning method can be used for locating leaking defects in lateral pipes made of insulating materials (e.g., plastic, clay, concrete, RCP, brick) by measuring the electrical current flow between a probe that travels in the pipe (a part of lateral where the probe is passing must be filled with water) and a surface electrode (a metal stake in the ground). If the pipe has no defects, the current flow is very low. However, various defects (structural, corrosion or joint defects) allow electric current to flow through the pipe wall when the probe center is close to the defect. Increased electrical current flow indicates pipe defects that allow liquids to flow into or out of the pipe, and the greater the electrical current the larger the pipe defect. The method is not applicable in metallic pipes (e.g., cast iron laterals).

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Ruston, LA