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LEAKAGE CONTROL AND UNACCOUNTED-FOR WATER ANALYSIS

Alex Rizzo (Engineer)
Malta Water Services Corporation

This paper gives an overview of the concepts and methodologies related to the practical implementation of leakage control and unaccounted-for water analysis. The paper delves into the various barriers and obstacles that a water utility will encounter, with particular reference to experience gained in the Maltese Islands. The following material is covered:

• Overview of the Maltese Islands; the local scenario.
• Unaccounted-for water; concepts and terminologies.
• The first major hurdle, understanding unaccounted-for Water.
• Developing a water balance, implementation of a regional zoning scheme, obstacles to be overcome.
• Real losses; implementation of the ideal methodology, restructuring, resource allocation and outsourcing.
• Apparent losses; implementation of specialized projects, utilization of expertise from the private sector.
• Sustaining the system; maintenance and database management issues.
• Training and leading staff, cultural and educational issues.

Overview of the Maltese Islands, the Local Scenario:

The Maltese Islands consist of three separate islands; Malta, which is approximately 95Km2 and houses around 180,000 premises, Gozo, which is approximately 26Km2 and houses around 20,000 premises and Comino, of negligible proportions. A total of nearly 370,000 habitants live on the islands, increasing to over 500,000 in the peak touristic season. The water distribution system is operated by one organization; the Government owned Water Services Corporation (WSC), employing around 1,200 full-time staff members.

Each and every premises on the Islands is metered and subsequently billed. The national water distribution network consists of around 3,400Km of assorted pipe network (mainly galvanized iron, cast iron, ductile iron and polyethylene), segmented into 8 Master Zones, 40 Cluster Zones and 300 zones. The WSC commenced studies and research into various schemes and techniques related to unaccounted-for water (UFW) way back in 1990. In 1994 a series of initiatives were implemented, to a large extent changing the methodologies and practices of the WSC in relation to UFW activities.

As a result of these initiatives, national system demand reached a peak in early 1995 before starting to drop. Notwithstanding a slight increase in billed consumption over the last 4 years, system demand has been reduced to 33% below its 1995 values, to an extent where the 1999 system demand now equals the 1989 system demand. Calculations indicate that national leakage has been halved, with leakage figures comparing favorably to international values. Optimum economic leakage targets have been set and, in some localities, already been achieved.

Unaccounted-for Water Concepts and Terminologies

The term Unaccounted-for Water (UFW) refers to an accumulated range of losses that will be experienced by a Water Utility when comparing the system demand of a hydraulic water network with the quantity of water that is acknowledged as consumed by the water consumers residing within the network. Throughout the paper, the following terminology is utilized:

• System Demand: This describes the quantity of water inputted into the water network, often also referred to as System Input or Production less Reserves. The system demand can be computed for any form of metered and hydraulically encapsulated water networks, such as Master Zones, Cluster Zones or Zones.
• Hydraulically Encapsulated Area: A part of the water distribution network that is separated from the remainder of the system by shut valves, capped mains and a minimum number of metered interaction points.
• Master Zone: A large hydraulically encapsulated segment of the Water Utility’s distribution network, comprising numerous zones, reservoirs, production sources, trunk/transfer mains, etc.
• Cluster Zone: A smaller, more manageable part of a master zone that is also hydraulically encapsulated and usually comprises a limited number of zones, reservoirs and production sources.
• Zone: A segment of the network, hydraulically encapsulated, with preferably solely one metered (and data logged) supply inlet, zone size ideally below 3,000 premises.

• Real Losses: This first component of UFW consists of all forms of leakage within the network, such as service pipe leakage, leakage on fittings, reservoirs, trunk/transfer/street mains, etc. Any leakage downstream of a production source and upstream of the consumer revenue meter is termed a real loss.
• Apparent Losses: This term sums three principal sources of UFW that result in water that is actually consumed (or utilized) but not successfully billed. For this reason these three components are not a ‘real loss’ (as is leakage) but an ‘apparent loss’.
• Metering Errors: This first component of the apparent loss range can be subdivided into two categories; A) revenue meter under-registration, resulting in a lower than actual computation of consumer water usage and B) production meter over-registration, resulting in a higher than actual computation of system demand.
• Water Theft: This second component of the apparent loss range consists of the illegal or unauthorized usage of water taken from the system.
• Billing Anomalies: This third component of the apparent loss range includes a multitude of factors that contribute to a distorted picture of legitimate consumer usage due to the ineffectiveness of the water utility’s billing system.

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