Water leaks can cause material damage, create additional consumption costs and reduce water pressure. Before finding nonvisible water leaks (water leaks underground). We have to determine how much water is been lost and the pipe system from which it is losing.
We use a range of methods to take trace line of pipe work and amount of water being lost.
Metallic Pipes can be traced by attaching a signal generator which sends a signal along the length of the pipe and this is detected above ground by a reciever tuned to the same frequency.
Non Metallic Pipes cannot be conduct the transmitted signal; this is overcome by:
- inserting a tracer wire inside the pipe, and sending the signal along the wire or,
- using a device to send alternating pressure or sound waves through the pipe, and the sounds are detected above by sensitive ground microphones.
There are several method used to detect water leaks:
a) Ground Microphones
When water escapes from a pipe under pressure, it creates a noise — metallic pipes create a higher frequency sound, plastic pipes create a lower sound. These sounds are picked up by extremely sensitive ground microphones, with high and low frequency filters.
b) Leak Noise Correlation
With correlation, the sound is electronically measured by microphones at two points,( usually at the boundary stopcock and the internal stopcock). The sounds are assessed by computer and the sound peak is calculated from both points.
c) Tracer Gas
An inert and harmless tracing gas, usually 95% Nitrogen and 5% Hydrogen is injected into the pipe. Hydrogen molecules are extremely small, and as they exit via the leak , they rise and permeate through the layers above, whether soil, concrete or tarmac. They can then be detected by extremely sensitive sensors, thus indicating the area of leakage.
d) Pipe Stopping (only for smooth bore pipes)
A small air bag is inserted along the pipe internally, then inflated to seal the pipe. That section of pipe is then pressurised by air, and if holds the pressure, there is no leak; if the pressure reduces, the leak is in that section. The air bag is repeatedly repositioned to give an accurate indication, often to within a few inches, of where the leak is.