Water Leaks Create Different Sounds.
Water leaking from an underground pipe normally generates an audible sound due to the water pressure. This leakage sound contains four elements:

1. Water flow sound
2. Impact sound
3. Friction sound of the water against the pipe
4. Pipe vibration sound


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Water leaks create different sounds.   Sound intensity increases with water pressure.

Various pipe materials transmit sound differently.

Higher frequencies are more attenuated (absorbed) in soil than lower frequencies.

Factors Affecting Leak Sounds & Our Ability to Hear Them:

  • Water Pressure in Pipe.
  • Type of pipe material and pipe diameter.
  • Soil type and soil compaction.
  • Ground surface for microphone: concrete versus soil.
  • Extraneous noises: wind, highways, buildings, machinery, etc.

Water Leak Surveys and Water Leak Pinpointing:

  • Water Leak Surveys:
  •               - Listen at hydrants, valves, meters, curb stops, and other exposed sections/fittings.
                  - No sounds at all, then no leak nearby.
  • Water Leak Pinpointing: 
  •               - Only after performing surveys.
                  - Between two loudest fittings (hydrants, meters, etc.).
                  - Directly over top of line.

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Leak survey at meters.                                    Water leak pinpointing.

What are Sounds of Leaks Like:

  • Good water pressure, corp leak or small leak: "hiss".
  • Good water pressure, main break or big leak: "whoosh".
  • Very close to leak (15-20 feet during pinpointing): rapid "thumping" noises of water against soil in cavity or "clink, clink" of small stones bouncing off pipe.
  • Water splashing on the pipe: may be close to leak or may be water traveling along pipe for long distance.
  • Pipe resonance noises (i.e., "hiss" or "whoosh"); always very constant.
  • Intermittent and on again / off again noises: not a leak.
  • "Um and ringing" : transformers, motors, or gas lines.
  • "Click, click, click" : meter turning (not a leak).

Advantage of an Acoustic Leak Detector:

  • Inexpensive.
  • Maintenance free and pretty reliable (Don't drop the sensor!).
  • User friendly and easy to operate.
  • Can be used inside of buildings for leaks inside of walls and under floors (turn off HVAC system and other building noises).
  • Almost never wrong: where leak is loudest is almost always where leak is located.
  • Last for many years: 10-15 years life expectancy.

Disadvantage of Accoustic Leak Detector:

  • Practice required to learn leak sounds and techniques.
  • Maximum depth for pinpointing: 1 to 1.5m for pinpointing.
  • Pinpointing over soft or grass cover more difficult.
  • Pinpointing is sometimes possible only at night.

Water Leak Surveys: How to do them:

  • For most complete surveys, listen at EVERY curb stop, meter, hydrant, valve, etc.
  • For iron and steel lines, listen at hydrants or Meters every 100 to 200m.
  • For AC pipe, listen at hydrants and at a curb stop/meter between them (max distance between points: 100m).
  • For 13mm to 150mm PVC pipe, (Max distance between points 150m).
  • For 150mm and larger PVC pipe, (Max distance between points 100m).
  • When listening at curb stops or meter boxes, pick side of street with shorter length services.
  • No leak sounds? Then, no leak nearby.

Listening at meter with FSB-8D.

Water Leak Pinpointing: How to do it:

  • Only after performing surveys.
  • Between two loudest fittings (hydrants, meters, etc.).
  • Directly over top of line.

1.  Locate Pipe with PL-960/PL-2000/NPL-100.

        - Mark water line with pipe locator between two loudest locations (curb stop, hydrant, valve, etc.).

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Pipe locator Induction Method.        External coil for insulated pipe & cables.

2.  Water Leak Detector.

        - Use Ground plate for street surfaces, sidewalks and concrete slabs.
        - Use pointed red or boring bars (push rods) in soft dirt and grass covered areas.
        - Listen every 50-60cm. Do not adjust volume and listen for 5-10 seconds only.


        - Stay directly over the pipe or the exact same distance on either side.
        - When loudest. then directly over leak.
        - Use visible display (LED meter, dial meter) in last 5-10 feet when "loudest" is heard to determine peak.

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Visible display on detectors.                   Loudest Point.

Confirmation survey.