bluezone group
  • Newcastle: +61 (0)2 4964 3500
  • Melbourne: +61 (0)3 8720 0300
  • Perth: +61 (0)8 6595 1500
How Does It Work?

How Does It Work?

1 Extra-Low Voltage (ELV) Electric Signals to Find Leaks

SewerSerpent® uses sophisticated software for analysis and detection of safe, Extra-Low Voltage (ELV) electric signal that is transmitted by the Scan Head. During a scan the electrical signal 'leaks' from the pipe via any defects near the Scan Head much the same way as water would. As the Scan Head is drawn through a pipe, defects in the pipe walls cause small changes in the electrical signal which are detected by the sensitive electronics in SewerSerpent®  and amplified for presentation to the operator. 

The 'electrical signal' used by the SewerSerpent® is fundamentally an electric current that is supplied from the Serpent Control Unit to the Scan Head. The current flows from the Scan Head and returns to the Serpent Control Unit, since electric current only flows in a complete circuit. 

2 The Ground Forms the Electrical Circuit 

The interesting thing about the SewerSerpent® is that the ground (that is, the dirt) is actually part of the electrical circuit! This might seem confusing or even impossible, since dirt is hardly a 'good' electrical conductor, but it does work, and there are many other electrical systems that use the ground as part of the circuit. 

There are even power systems known as Single Wire Earth Return (SWER) which use this principle to deliver electrical power over large distances. The electrical signals used by SewerSerpent® are much smaller than in SWER power systems, so the amount of current flowing through the ground/dirt is much lower, but the fundamental principles and physics are the same. 

3 Understanding the Operation 

To understand the operation of SewerSerpent® let's start with the simple circuit below.



The voltage source will drive current around the loop (circuit), and the current meter will indicate how much current is flowing.


Fundamentally, this is the same circuit as when current is flowing through the earth, but the resistor is replaced by the resistance of the earth between the two earth stakes.


The SewerSerpent® operates on this basic principle, but to understand how this helps us locate defects in pipes we'll first look at an example where the pipe is defect free, and perfectly insulating. In this case there is no path for current to flow from the scan head (which is inside the pipe) back to the earth stake


On the other hand if there is a defect in the pipe, then current can flow out through the defect and into the earth, where it can return to the earth stake. 


The current meter in the Serpent Control Unit detects this current flow, and presents a graph to the operator in real time as the scan head is drawn through the pipe. 

4 Further Information

For further information on SewerSerpent® operation please download this document.

UV-FLY-0031_A_SewerSerpent-_-_How_does_it_work UV-FLY-0031_A_SewerSerpent-_-_How_does_it_work (827 KB)