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
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
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.