6
Hand probe
For normal soft ground surfaces the single pointed extension rod should be connected, do
not over tighten the screw thread. For direct contact with underground fittings via access
covers it may be necessary to use the second extension rod. To do assemble this remove
the single rod and connect the extension rod and re-fit the pointed rod again. If the rods have
been over tightened, spanner slots allow easy removal.
Surveying
The leak location can be narrowed down by listening at accessible contact points such as
meters, hydrants, valves and stop-taps, which provide points of good sound pick-up
particularly if the pipe is metallic. Use the hand-probe/extension rod to listen at these
points.
If there are no accessible contact points or if the pipe is of non-metallic material use the
microphone foot for listening, placing the foot over the pipe route in the area of the
suspected leak. Move along the pipe route listening at each accessible pipe-fitting or at
regular positions on the ground until you have identified the area of maximum noise level.
Note
: When you are listening on pipe-fittings the location of the point of maximum noise will
probably not indicate the leak position, only the fitting closest to the leak. The noise level will
also appear stronger where there is less thickness of ground or other material for it to pass
through. The leak noise will follow the path of least resistance.
Pinpointing the leak position
Pinpointing the leak position involves a process of comparing a number of leak noises.
Select the most suitable sensor device; the microphone foot for hard ground surfaces or the
hand probe for soft ground.
Press the trigger to operate the Bmic and adjust the headphone volume control to a
comfortable listening level. Once you have listened to the noise through the headphones,
release the trigger to switch off the amplifier and move the microphone foot or hand probe to
the next test position.
Repeat the sequence to listen to each of the test locations moving along the pipe route in
the direction where signal strength is increasing. If the leak noise level falls you have
passed the leak and should go back and reduce the distance that you move between
measurements. The loudest leak noise will then indicate the location of the leak bearing in
mind the ground conditions already mentioned.
