Quantifying Meter Under-Registration Caused by the Ball Valves of Roof Tanks (for Indirect Plumbing Systems)

The concept of Real and Apparent Water Loss has been constantly advocated by the International Water Association in a drive to clarify the different components through which a water utility will produce water but not receive corresponding revenues. The difference between a Real and an Apparent Water Loss is quite basic: A Real Loss is water lost through a distribution network as leakage, hence is quite ‘really’ a loss as no one stands to gain from it! An Apparent Loss consists of water that is produced, distributed and ultimately consumed, but not paid for by the consumer. The paper shall review the four components forming Apparent Water Losses, shall detail an in-depth case study aimed at quantifying one of these four components (for a particular scenario), and shall conclude with a proposal for a more robust performance indicator for Apparent Water Loss control. The case study in question was carried out with the assistance of the University of Malta and the Maltese national water utility; the Water Services Corporation.