Finding and Repairing Leaks

Training students in acoustic leak detection at the City of Cerritos, CALeakCollage3

Finding and fixing underground leaks can save millions of gallons of water, but you first need to find them. Different leak detection technologies are needed for different types of leaks and pipeline materials.

 

Types of Leaks


LEAK TYPE


DESCRIPTION

Main LeaksLeaks range from 1 gallon per minute (gpm) to over 1,000 gpm; caused by corrosion, excessive pressure, improper installation, settlement, and overloading.
Service Line LeaksLeaks range from a low of 0.5 gpm to over 15 gpm; can be caused by a variety of factors.
Residential Meter-Box LeaksLeaks range from less than 1 gpm to 10 gpm; can be caused by damaged or broken angle stops, couplings, broken meters, etc.
Residential LeaksLeaks range from less than 1 gpm to 15 gpm; can be caused by holes, breaks, inefficient hose-bib or shutoff valves, interior plumbing lines, or fixtures.
Valve LeaksLeaks range from 1 gpm to 500 fpm; caused by loose packing, broken parts, etc.
Miscellaneous LeaksCan be caused by excessive pressure, settlement, overloading, improper installation, improper materials and operation.
Source: USEPA State of Technology for Rehabilitation of Water Distribution Systems, March 2013, Table 8-2

Leak Detection Technologies


TECHNIQUES


DESCRIPTION

Visual SurveyMost basic form of leak detection: looking for signs of leaks (e.g., water pooling on the surface).
Acoustic Survey SoundingFrequency and magnitude of noise generated by a leak varies with the type of leak, pipe material, diameter and pressure.
Comprehensive SurveyListens to all available fittings on the pipe and service connections (time consuming but effective).
General SurveyUses geophones and leak noise correlators to pinpoint leaks; less suited to non-metallic pipes.
Step TestingPinpoints leaks by isolating sections of main.
Noise Logger SurveyMost useful for areas with high background noise.
Leak Noise MappingMost appropriate for areas with high density hydrants.
Source: USEPA 2013, Table 8-3

Leak Repairs, Rehabilitations and Renewals (Replacements)

The actual useful lives of water distribution systems vary significantly.


WATER SYSTEM COMPONENT


EFFECTIVE USEFUL LIFE (YEARS)

Mains and Distribution Pipes


35-40

Valves


35-40

Service Lines


30-50

Hydrants


40-60

Meters


10-15

Source: USEPA Asset Management: A Handbook for Small Water Systems, September 2003

 

 

The effective useful life (EUL) of any particular remediation action taken depends on whether it is a repair, a rehabilitation or a renewal.

  • Repairs remedy a leak but do not increase either the capacity or the condition of the water distribution system. Consequently, irrespective of whether a particular type of repair (patch, clamp, etc.) may be deemed to have a long life (e.g., >20 years), the EUL of the repair is capped by the remaining useful life (RUL) of the water system at the point of the repair.
  • Rehabilitations increase the remaining useful life of the water system by relining pipes, increasing the time over which the pipes can productively do their job.
  • Renewals involve comprehensive repair, rehabilitation, and replacement of portions of mains and/or service lines. Renewals essentially re-set the clock on that portion of the water distribution system to the beginning of its service life.

The substantial cost and need for extensive repairs, rehabilitations and renewals of buried water infrastructure have spurred advances in materials and techniques that minimize the high cost of excavation. Significant savings can now be realized by in-place repairs and rehabilitations, such as slip-lining corroded pipes with PVC sleeve inserts and robotic spraying of pipeline interiors to rebuild eroded linings. When excavation is needed but the existing pipeline is deemed structurally sound, water utilities can choose from a variety of pipeline exterior wrapping materials and techniques. And when a segment of pipeline needs to be replaced, non-corrodible, long-lived PVC pipes are often the material of choice.

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