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

SOUNDS FROM WATER LEAKS: TRANSMISSION THROUGH PIPE WALLS AND SOIL, FACTORS THAT IMPACT SOUND TRANSMISSION.

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

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Various pipe materials transmit sound differently.

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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.

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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.

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Pinpointing.

        - 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.

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Confirmation survey.