A Practical Guide For Underground Services Location and CCTV Drainage Surveys

Electronic Tracing - Foul And Storm Water Sewers

The use of dye to trace drainage routes is not allowed in some areas, and it only proves connectivity. It is for this reason we use electro-detection. A transmitting sonde (a sausage shaped transmitter) attached to a flex-rod (a plastic glass fibre rod coiled on a rotating steel caged spool) is introduced into the sewer at an inspection pit and manually pushed down the pipe. Its progress is monitored and positioned above ground using a RD 4000 locator. It cannot be assumed that the sonde is lying centrally in the pipe, but a position and depth accuracy of ± 10% of depth plus twice diameter of pipe can be expected.

What can go wrong
A. It is not always possible to progress through debris and blockages.
B. For larger diameter pipes the sonde may position itself at the side of the pipe or the flex rod bunches if the progress of the sonde is impeded.
This method of survey will only provide the sewer route, and will NOT identify node points (remote gulley connections etc.). If node points are required a CCTV camera unit with sonde enables a visual location.

Previous Page | Contents | Next Page