Key Factors Affecting Water Meter Accuracy

Organization: 
Institute for Water Technology (Spain)

As any other measuring device, a water meter is not an ideal instrument and is not capable of registering the exact amount of water consumed by a user. Every water meter, no matter its type, has considerable measuring limitations. Often, part of the water that is consumed is not registered and therefore not charged to the customer. Other times, depending on the water meter technology, some particular factors may lead to the opposite result, that is, to an over registration of the water consumption. In any of these two cases, since water meter inaccuracies are recognised as a critical component of apparent losses, it is important to be capable of quantifying the magnitude of these measuring errors.

Nowadays there is a general lack of information, based on real data, about the actual effect of different parameters in the performance of water meters. Hence, technical staff in the water utility has to evaluate or estimate water meter accuracy, and analyse the factors that may have any influence on it, without the help of bibliographic reference or external experience.

This paper presents real field and laboratory data on how several factors may affect the water meter accuracy for both, domestic and industrial type of meters, and different technologies, single jet, multiple jet, oscillating piston, Woltman and Tangential meters. Particularly the influence of the following parameters in the water meter metrology will be analysed: mounting position, velocity profile distortions, fatigue tests, depositions, partial blockage of the strainer or the water meter inlet, incorrect water meter sizing, water consumption patterns and the presence of user’s storage tanks. As a result of the experiments it has been clearly shown that not every water meter has the same sensitivity to the previous parameters. Furthermore, diverse meter models of the same technology present very different behaviours depending on the specific construction characteristics of each instrument. Consequently, to reduce the magnitude of the apparent losses and to guaranty an accurate water measurement, it is not only important to select the adequate metering technology but also the right construction that suits the specific characteristics of the water supply system.

The paper is divided into two parts. The first dealing with factors that may affect domestic water meter accuracy and the second describing the most common problems in registering non-domestic water consumption.

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